Chest Physiotherapy and Airway Clearance Devices

Number: 0067

(Replaces CPBs 252, 280, 333)

Table Of Contents

Policy
Applicable CPT / HCPCS / ICD-10 Codes
Background
References

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Policy

Scope of Policy

This Clinical Policy Bulletin addresses chest physiotherapy and airway clearance devices.

1. Medical Necessity 

   1. Aetna considers the folowing interventions by a respiratory therapist medically necessary:

      1. Home chest physiotherapy upon the initial prescription of chest physiotherapy to stabilize the member and to train family members or caregivers to administer chest physiotherapy;
      2. Chest physiotherapy when the member’s pulmonary condition is unstable;

      Note: Chest physiotherapy by a respiratory therapist is not considered medically necessary for persons whose pulmonary condition is stable, as chest physiotherapy can be competently administered at home by a family member or caregiver.

   2. Aetna considers the following airway clearance devices medically necessary durable medical equipment (DME) to assist in mobilizing respiratory tract secretions for members with the conditions that are indicated below:

      1. Airway oscillating devices (e.g., Flutter and Acapella) for cystic fibrosis (CF), chronic bronchitis, bronchiectasis, immotile cilia syndrome (also known as primary ciliary dyskinesia) and asthma;
      2. Mechanical percussors (e.g., Fluid Flo, Frequencer, and VibraLung Acoustical Percussor) for CF, chronic bronchitis, bronchiectasis, immotile cilia syndrome, and asthma;
      3. Positive expiratory pressure (PEP) mask for CF, chronic bronchitis, immotile cilia syndrome, asthma, and chronic obstructive pulmonary disease (COPD);

   3. Aetna considers high-frequency chest compression systems (e.g., the AffloVest, the Frequencer, the Monarch Airway Clearance System, the SmartVest, the MedPulse Respiratory Vest System, the Vest Airway Clearance System, the ABI Vest, Respin11 Bronchial Clearance System, and the InCourage Vest/System) medically necessary DME in lieu of chest physiotherapy for the following indications, where there is a well documented failure of standard treatments to adequately mobilize retained secretions:

      1. Bronchiectasis, confirmed by CT scan, characterized by daily productive cough for at least 6 continuous months or by frequent (i.e., more than 2 times/year) exacerbations requiring antibiotic therapy; 
      2. Cystic fibrosis or immotile cilia syndrome; 
      3. The member has one of the following neuromuscular disease diagnoses:
         
         
         1. Acid maltase deficiency; or
         2. Anterior horn cell diseases, including amyotrophic lateral sclerosis; or
         3. Hereditary muscular dystrophy;or
         4. Multiple sclerosis; or
         5. Myotonic disorders; or
         6. Other myopathies; or
         7. Paralysis of the diaphragm; or
         8. Post-polio; or
         9. Quadriplegia regardless of underlying etiology.
            

      4. Lung transplant recipients, within the first 6 months post-operatively, who are unable to tolerate standard chest physiotherapy.;
         

   4. Aetna considers mechanical in-exsufflation devices medically necessary DME for persons with a neuromuscular disease (e.g., amyotrophic lateral sclerosis, congenital myopathies, inclusion body myositis, muscular dystrophy, myasthenia gravis, poliomyelitis, progressive bulbar palsy, spinal muscular atrophy, high spinal cord injury with quadriplegia) that is causing a significant impairment of chest wall and/or diaphragmatic movement and for whom standard treatments (e.g., chest percussion and postural drainage, etc.) have not been successful in adequately mobilizing retained secretions.

2. Experimental and Investigational

   Aetna considers the following devices or interventions experimental and investigational because the effectiveness of these approaches has not been established:

   1. High-frequency chest compression systems for other indications in members who do not meet medical necessity criteria above (e.g., alpha 1-antitrypsin deficiency, anoxic brain injury, cerebral palsy, CFTR-related metabolic syndrome, childhood atelectasis, chronic inflammatory demyelinating polyneuropathy, coma, Cri-du-Chat syndrome, dyspnea in chronic obstructive pulmonary disease, plastic bronchitis, individuals with acute pneumonic respiratory failure receiving mechanical ventilation, individuals in a chronic vegetative state or in a coma, individuals with Rett syndrome, interstitial lung disease, kyphosis, leukodystrophy, protein alveolar proteinosis, scoliosis, stiff-person (stiff-man) syndrome, and Zellweger syndrome; not an all-inclusive list); because their effectiveness for these indications has not been established;
      
   2. Intrapulmonary percussive ventilators (IPV) (e.g., the Impulsator F00012) for all indications (e.g., bronchiectasis, COPD, CF, neuromuscular conditions associated with retained airway secretions or atelectasis, and post-operative pulmonary complications; not an all-inclusive list) because there is insufficient evidence supporting their effectiveness;
   3. High-frequency oscillation therapy for the treatment of bronchitis, and secretion-induced atelectasis because there is insufficient evidence supporting its effectiveness;
   4. The Volara System Oscillation & Lung Expansion (OLE) therapy device for the treatment of asthma, cystic fibrosis, middle lobe syndrome, and other respiratory disorders because there is insufficient evidence supporting its effectiveness;
   5. The Simeox Airway Clearance Technology bronchial drainage device for the treatment of cystic fibrosis and all other indications because there is insufficient evidence supporting their effectiveness.

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Table:

CPT Codes / HCPCS Codes / ICD-10 Codes

Code	Code Description
Home Chest Physiotherapy:
CPT codes covered if selection criteria are met:
94667, 94668	Manipulation chest wall, such as cupping, percussing and vibration to facilitate lung function; initial demonstration and/or evaluation or subsequent
94669	Mechanical chest wall oscillation to facilitate lung function, per session
97124	Therapeutic procedure, one or more areas, each 15 minutes; massage, including effleurage, petrissage and/or tapotement (stroking, compression, percussion)
HCPCS codes covered if selection criteria are met:
G0237	Therapeutic procedures to increase strength or endurance of respiratory muscles, face-to-face, one-on-one, each 15 minutes (includes monitoring)
G0238	Therapeutic procedures to improve respiratory function, other than described by G0237, one-on-one, face-to-face, per 15 minutes (including monitoring)
ICD-10 codes covered if selection criteria are met:
E84.0 - E84.9	Cystic fibrosis
G12.20 - G12.29	Motor neuron disease
G70.00 - G73.7	Diseases of myoneural junction and muscle
G82.20 - G82.54	Paraplegia (paraparesis) and quadriplegia (quadriparesis)
J40 - J47.9	Chronic lower respiratory diseases
J98.6	Disorders of diaphragm
Q33.4	Congenital bronchiectasis
Q89.3	Situs inversus [immotile cilia syndrome]
S12.000+ - S12.9xx+	Fracture of cervical vertebra and other parts of the neck
S14.101S - S14.109S	Unspecified injury of cervical spinal cord, sequela
S14.101+ - S14.109+	Unspecified injury of cervical spinal cord
S14.2xxS - S14.9xxS	Injury of nerves at neck level, sequela
S22.000+ - S22.089+	Fracture of thoracic vertebra
S24.101S - S24.109S	Unspecified injury of thoracic spinal cord, sequela
S24.101+ - S24.109+	Unspecified injury of thoracic spinal cord
S24.2xxS - S24.9xxS	Injury of nerves at thorax level, sequela
S34.101S - S34.109S	Unspecified injury of lumbar spinal cord, sequela
S34.131S - S34.139S	Other and unspecified injury to sacral spinal cord, sequela
S34.21xS - S34.9xxS	Injury of nerves at lumbar and sacral spinal cord and nerves at abdomen, lower back and pelvis level, sequela
Z94.2	Lung transplant status
Airway Clearance Devices:
Flutter / Acapella Device:
HCPCS codes covered if selection criteria are met:
S8185	Flutter device
ICD-10 codes covered if selection criteria are met:
E84.0 - E84.9	Cystic fibrosis
J41.0 - J42	Chronic bronchitis
J45.20 - J45.998	Asthma
J47.0 - J47.9	Bronchiectasis
Q33.4	Congenital bronchiectasis
Q89.3	Quantitative Pupillometry/Pupillography
Z94.2	Lung transplant status
Mechanical Percussors:
HCPCS codes covered if selection criteria are met:
E0480	Percussor, electric or pneumatic, home model
ICD-10 codes covered if selection criteria are met:
E84.0 - E84.9	Cystic fibrosis
J41.0 - J42	Chronic bronchitis
J45.20 - J45.998	Asthma
J47.0 - J47.9	Bronchiectasis
Q33.4	Congenital bronchiectasis
Q89.3	Situs inversus [immotile cilia syndrome]
Z94.2	Lung transplant status
Positive Expiratory Pressure (PEP):
HCPCS codes covered if selection criteria are met:
E0484	Oscillatory positive expiratory pressure device, non-electric, any type, each
ICD-10 codes covered if selection criteria are met:
E84.0 - E84.9	Cystic fibrosis
J40 - J47.9	Chronic lower respiratory diseases
Q89.3	Quantitative Pupillometry/Pupillography
High-frequency chest compression systems:
HCPCS codes covered if selection criteria are met:
A7025	High frequency chest wall oscillation system vest, replacement for use with patient owned equipment, each
A7026	High frequency chest wall oscillation system hose, replacement for use with patient owned equipment, each
E0483	High frequency chest wall oscillation air-pulse generator system, (includes hoses and vest), each
ICD-10 codes covered if selection criteria are met:
A15.0	Tuberculosis of lung [tuberculous bronchiectasis]
B91	Sequlea of poliomyelitis
G14	Postpolio syndrome
E84.0 - E84.9	Cystic fibrosis
G12.0 - G12.9	Spinal muscular atrophy and related syndromes
G35	Multiple sclerosis
G82.20 - G82.54	Paraplegia (paraparesis) and quadriplegia (quadriparesis) [regardless of underlying etiology]
G71.2	Congenital myopathies
G71.11 - G71.19	Myotonic disorders
G72.0 - G72.9	Other and unspecified myopathies
J47.0 - J47.9	Bronchiectasis
J98.6	Disorders of diaphragm [paralysis of the diaphragm]
Q33.4	Congenital bronchiectasis
Q89.3	Quantitative Pupillometry/Pupillography
Z94.2	Lung transplant status
ICD-10 codes not covered for indications listed in the CPB (not all-inclusive):
E71.510	Zellweger syndrome
E71.520 - E71.529	X-linked adrenoleukodystrophy
E75.29	Other sphingolipidosis
E88.81	Metabolic syndrome [CFTR-related metabolic syndrome]
E88.89	Other specified metabolic disorders [CFTR-related metabolic syndrome]
F84.2	Rett's syndrome
G25.82	Stiff-Man Syndrome
G61.81	Chronic inflammatory demyelinating polyneuritis
G80.0 - G80.9	Cerebral palsy
G93.1	Anoxic brain damage, not elsewhere classified
J18.9	Pneumonia, unspecified organism
J40	Bronchitis, not specified as acute or chronic [Plastic bronchitis]
J44.0 – J44.9	Chronic obstructive pulmonary disease
J84.01	Alveolar proteinosis
J84.10 - J84.9	Other interstitial pulmonary diseases
J96.00 - J96.02	Acute respiratory failure
J98.11	Atelectasis [childhood atelectasis]
M40.00 - M40.299	Kyphosis
M41.00 - M41.9	Scoliosis
P28.0	Primary atelectasis of newborn
P28.10 - P28.19	Other and unspecified atelectasis of newborn
Q67.5	Congenital deformity of spine
Q76.0 - Q76.419	Congenital malformations of spine
Q93.4	Deletion of short arm of chromosome 5 [Cri-du-Chat syndrome]
R40.20+ - R40.236+	Coma
R40.3	Persistent vegetative state
Mechanical Insufflation-Exsufflation Devices:
HCPCS codes covered if selection criteria are met:
A7020	Interface for cough stimulating device, includes all components, replacement only
E0482	Cough stimulating device, alternating positive and negative airway pressure
ICD-10 codes covered if selection criteria are met:
A80.0 - A80.9	Acute poliomyelitis
G12.0 - G12.1	Infantile spinal muscular atrophy, type I [Werdnig-Hoffman] and other inherited spinal muscular atrophy [Progressive bulbar palsy of childhood [Fazio-Londe]]
G12.20 - G12.29	Motor neuron disease
G12.8 - G12.9	Other and unspecified spinal muscular atrophies and related syndromes
G70.00 - G70.01	Myasthenia gravis
G71.00 - G71.09	Muscular dystrophy
G71.2	Congenital myopathies
G72.41	Inclusion body myositis [IBM]
G82.20 - G82.54	Paraplegia (paraparesis) and quadriplegia (quadriparesis)
G70.00 - G73.7	Diseases of myoneural junction and muscle
J98.6	Disorders of diaphragm
S12.000+ - S12.9xx+	Fracture of cervical vertebra and other parts of the neck
S14.0XXS - S14.109S	Unspecified injury of cervical spinal cord, sequela
S14.101S - S14.109S	Unspecified injury of cervical spinal cord, sequela
S14.101+ - S14.109+	Unspecified injury of cervical spinal cord
S14.2xxS- S14.9xxS	Injury of nerves at neck level, sequela
Intrapulmonary percussive ventilators (IPV):
HCPCS codes not covered for indications listed in the CPB:
E0481	Intrapulmonary percussive ventilation system and related accessories
ICD-10 codes not covered for indications listed in the CPB (not all-inclusive):
E84.0 - E84.9	Cystic fibrosis
J44.0 - J44.9	Chronic obstructive pulmonary disease
J47.0 - J47.9	Bronchiectasis
J95.00 - J95.5, J95.811 - J95.859, J95.89	Postprocedural respiratory complications
Continuous high-frequency oscillation therapy:
CPT codes not covered for indications listed in the CPB:
Continuous high-frequency oscillation therapy - no specific code:
ICD-10 codes not covered for indications listed in the CPB (not all-inclusive):
J40	Bronchitis, not specified as acute or chronic
J98.11	Atelectasis [childhood atelectasis]
Volara system oscillation & lung expansion (OLE) therapy device:
HCPCS codes not covered for indications listed in the CPB:
Volara system oscillation & lung expansion (OLE) therapy device-no specific code
ICD-10 codes not covered for indications listed in the CPB:
E84.0 – E84.9	Cystic fibrosis
J45.20 – J45.998	Asthma
J98.19	Other pulmonary collapse [Middle lobe syndrome]
J98.8 – J98.9	Other specified respiratory disorders
Simeox airway clearance technology bronchial drainage device:
HCPCS codes not covered for indications listed in the CPB:
Simeox airway clearance technology bronchial drainage device – no specific code
ICD-10 codes not covered for indications listed in the CPB:
E84.0 – E84.9	Cystic fibrosis

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Background

Cystic fibrosis (CF), chronic bronchitis, bronchiectasis, immotile cilia syndrome, asthma, and some acute respiratory tract infections can lead to abnormal airway clearance or increase sputum production.  Airway secretions are cleared by mucociliary clearance (MCC), in addition to other mechanisms such as cough, peristalsis, two-phase gas-liquid flow and alveolar clearance.  The underlying pathology of abnormal airway clearance differs from one illness to another.  Chest physiotherapy (CPT) is a treatment program that attempts to compensate for abnormal airway clearance.  By removing mucopurulent secretions, it decreases airway obstruction and its consequences, such as atelectasis and hyperinflation; furthermore, physiotherapy can decrease the rate of proteolytic tissue damage by removing infected secretions.  Methods to improve removal of tenacious lung secretions in patients with CF contribute to slowing the decline in respiratory function.

The standard dependent method of pulmonary care remains clapping, vibration and compression, together with postural drainage and assisted coughing.  Most practitioners prescribe 20 to 30-min CPT sessions 1 to 3 times a day, depending on the severity of disease and the presence of intercurrent infection.

Respiratory therapists can teach family members or other informal caregivers to competently administer manual CPT to children and others who are incapable of doing it for themselves.  The National Heart Lung and Blood Institute (1995) of the National Institutes of Health states: "Chest therapy consists of bronchial, or postural, drainage, which is done by placing the patient in a position that allows drainage of the mucus from the lungs.  At the same time, the chest or back is clapped (percussed) and vibrated to dislodge the mucus and help it move out of the airways.  This process is repeated over different parts of the chest and back to loosen the mucus in different areas of each lung.  This procedure has to be done for children by family members but older patients can learn to do it by themselves.  Mechanical aids that help chest physical therapy are available commercially."

Different types of airway clearance devices have been developed for independent use, which require little or no assistance by others.  When a competent care giver is not available to administer CPT manually, specific alternative methods may be utilized.  Many of these techniques have been developed and studied using CF patients.

De Boeck and colleagues (2008) noted that airway clearance techniques are an important part of the respiratory management in children with CF, bronchiectasis and neuromuscular disease.  They are also, however, frequently prescribed in previously healthy children with an acute respiratory problem with the aim to speed up recovery.  These investigators reviewed the evidence behind this use of airway clearance techniques in children without underlying disease.  They stated that few studies have been performed; many different techniques are available and the therapies used are often poorly specified.  It is necessary to name the specific airway clearance technique used in treatment rather than to just state "chest physiotherapy," a term that is often confused with chest clapping or vibration plus postural drainage.  There is little evidence that airway clearance techniques play a role in the management of children with an acute respiratory problem.  Physicians routinely prescribing airway clearance techniques in previously healthy children should question their practice.

High Frequency Chest Compression Systems

A high-frequency chest wall compression device (The Vest Airway Clearance System, formerly known as the ThAIRapy Vest, ABI Vest) (Advanced Respiratory, St. Paul, MN) is an inflatable vest connected to a compressor that provides external high-frequency chest wall oscillation.  The vest is connected via tubing to an air pulse delivery system.  The patient then uses a foot pedal to apply pressure pulses that cause the vest to inflate and deflate against the thorax creating an oscillatory or vibratory motion.

High-frequency chest compression devices have been shown to increase sputum production in CF patients.  Cystic fibrosis is caused by abnormal chloride ion transport on the apical surface of epithelial cells in exocrine gland tissues.  The abnormally composition of secretions from affected epithelial surfaces results in increased viscosity.  It has been theorized that high-frequency chest compression devices are particularly effective in clearing the abnormal secretions of CF because vibratory shear forces facilitate expectoration by reducing the viscosity of these secretions, much in the same way that shaking jello causes it to become fluid.  However, high-frequency chest compression vests have not been proven to be more effective than manual chest physiotherapy.  It can be used in place of manual chest physiotherapy for patients with CF where manual chest physiotherapy is unavailable.

High-frequency chest wall compression devices have been promoted for use in conditions other than CF, including non-CF bronchiectasis.  However, there are no adequate published controlled clinical studies of high-frequency chest compression devices for conditions other than CF.  Given the unique pathophysiology of CF resulting in the abnormal composition of CF secretions, evidence of the effectiveness of high-frequency chest wall compression devices in CF can not be extrapolated to other pulmonary conditions.  The Vest was cleared by the Food and Drug Administration (FDA) for a wide variety of pulmonary conditions based on a 510(k) pre-market notification; thus the manufacturer was not required to submit the type of evidence of effectiveness that would be required to support a pre-market approval (PMA) application.

In addition, there are no adequate studies comparing high-frequency chest compression to other, relatively simple and substantially less expensive devices (e.g., Flutter, Acapella) that apply high-frequency oscillation to the airway.

The American College of Chest Physicians' evidence-based clinical practice guidelines on non-pharmacologic airway clearance therapies (McCool and Rosen, 2006) recommend oscillatory devices (e.g., Flutter, IPV, and HFCWO) be considered as an alternative to chest physiotherapy only in CF patients.

The Vest is only available for purchase (it can not be rented); the air pulse delivery system (an air-pulse generator) and flexible hoses are available for rental or purchase.

There is controversy surrounding the use of high-frequency chest physiotherapy devices for indications other than CF.

Yuan and colleagues (2010) stated that airway secretions and infections are common in cerebral palsy (CP) and neuromuscular diseases.  Chest physiotherapy is standard therapy but effort is substantial.  High-frequency chest wall oscillation (HFCWO) is used in CF, but tolerability and safety data in cerebral palsy and neuromuscular disease are limited.  These researchers performed a prospective, randomized, controlled trial of HFCWO and standard CPT in patients with neuromuscular disease or CP.  Outcome measures included respiratory-related hospitalizations, antibiotic therapy, chest radiographs, and polysomnography.  Caregivers were questioned regarding therapy adherence.  A total of 28 participants enrolled, 23 completed (12 CPT, mean study period 5 months).  No adverse outcomes were reported.  Adherence to prescribed regimen was higher with HFCWO (p = 0.036).  These findings suggest safety, tolerability, and better compliance with HFCWO.  Improvement in airway clearance may help prevent hospitalizations.  The authors noted that larger controlled trials are needed to confirm these results.

Drosman and Jones (2005) noted that, in the pediatric population, HFCWO is most widely used in children with CF, but that children with developmental disorders involving neuromuscular dysfunction also have impaired airway clearance with or without ventilatory dependence.  The authors stated that "[l]arge, long-term studies are needed examining HFCC in the patients with developmental disorders."

In an "exploratory" randomized controlled trial, Lange et al (2006) assessed changes in respiratory function in patients with amyotrophic lateral sclerosis (ALS) after using HFCWO.  This was a 12-week study of HFCWO in patients with probable or definite ALS, an Amyotrophic Lateral Sclerosis Functional Rating Scale respiratory subscale score less than or equal to 11 and greater than or equal to 5, and forced vital capacity (FVC) greater than or equal to 40 % predicted.  A total of 46 patients were enrolled (58.0 +/- 9.8 years; 21 men, 25 women); 22 used HFCWO and 24 were untreated.  Only 35 completed the trial: 19 used HFCWO and 16 untreated.  Results were reported per-protocol, rather than by intention-to-treat.  HFCWO users had less breathlessness (p = 0.021) and coughed more at night (p = 0.048) at 12 weeks compared to baseline.  At 12 weeks, HFCWO users reported a decline in breathlessness (p = 0.048); non-users reported more noise when breathing (p = 0.027).  There were no significant differences in FVC change, peak expiratory flow, capnography, oxygen saturation, fatigue, functional quality of life, or transitional dyspnea index.  When patients with FVC between 40 and 70 % predicted were analyzed, FVC showed a significant mean decrease in untreated patients but not in HFCWO patients; HFCWO patients had significantly less increased fatigue and breathlessness.  Satisfaction with HFCWO was 79 %.  The authors concluded that HFCWO was well-tolerated, considered helpful by a majority of patients, and decreased symptoms of breathlessness.  In patients with impaired breathing, HFCWO decreased fatigue and showed a trend toward slowing the decline of forced vital capacity.  The investigators explained that the study was exploratory in nature, and was not sufficiently powered to detect significant differences in clinical outcomes such as pulmonary complications, hospitalizations or mortality.

On the other hand, Chaisson et al (2006) did not find HFCWO to be of significant help to patients with ALS.  These investigators evaluated the effectiveness of HFCWO administered through the Vest Airway Clearance System when added to standard care in preventing pulmonary complications and prolonging the time to death in patients with ALS.  A total of 9 patients with a diagnosis of ALS and concurrently receiving non-invasive ventilatory support with bi-level positive airway pressure (BiPAP) were recruited from an outpatient clinic.  Four patients were randomized to receive standard care and 5 patients to receive standard care plus the addition of HFCWO administered twice-daily for 15-min duration.  Longitudinal assessments of oxyhemoglobin saturation, forced FVC, and adverse events were obtained until time of death.  Pulmonary complications of atelectasis, pneumonia, hospitalization for a respiratory-related abnormality, and tracheostomy with mechanical ventilation were monitored throughout the study duration.  No differences were observed between treatment groups in relation to the rate of decline in FVC.  The addition of HFCWO airway clearance failed to improve time to death compared to standard treatment alone (340 days +/- 247 versus 470 days +/- 241; p = 0.26).  The random allocation of HFCWO airway clearance to patients with ALS concomitantly receiving BiPAP failed to attain any significant clinical benefits in relation to either loss of lung function or mortality.  This study does not exclude the potential benefit of HFCWO in select patients with ALS who have co-existent pulmonary diseases, pre-existent mucus-related pulmonary complications, or less severe levels of respiratory muscle weakness.

The Frequencer (Dymedso, Inc., Boisbriand, Quebec, Canada) is a device that provides airway clearance therapy and promotes bronchial drainage by inducing vibration in the chest walls.  It induces oscillatory sound waves in the chest by means of an electro-acoustical transducer (referred to as the "Power Head"), which is placed externally on the user's chest.  The Power Head is connected to a frequency generator that is capable of producing frequencies between 20 and 100 Hz, and induces sound waves in the user's chest for the purpose of loosening mucus deposits.

The Frequencer device provides airway clearance by inducing oscillatory sound waves in the chest by means of an electro-acoustical transducer placed externally on the patient's chest.  The transducer is connected to a frequency generator which is capable of producing frequencies between 20 and 100 Hz.  The vibrations in the patient's chest are effective in loosening mucus deposits and promoting bronchial drainage.  The Frequencer consists of 2 parts, a control unit and a transducer.  The user places the transducer on the chest.  The frequency (adjustable between 20 and 100 HZ) and the volume are adjusted in the control unit to create sympathetic resonance that can be felt in the lungs.  According to the manufactuer, there are significant differences between other high frequency percussors and the Frequencer. Specifically: other devices deliver a frequency pounding or striking action, similar to clapping, to a patient's chest to loosen mucus. The Frequencer uses a different operating principle: higher frequency acoustic waves to excite resonance in the chest, and acoustic wave action makes the Frequencer appropriate patients who are: under 3 years of age; elderly and fragile; agitated; immobilized; obese; and status/post surgery.

Cantin et al (2006) stated that clearance of mucus from airways is the cornerstone of therapy for lung disease in patients with CF.  These investigators described the operation of the Frequencer, a novel respiratory physiotherapy device comprised of an electro-acoustical transducer.  They hypothesized that the Frequencer would be a safe and effective therapy to help clear secretions from the airways of subjects with CF.  A total of 22 individuals with CF were recruited to this study comparing sputum production during conventional chest physiotherapy (CCPT) and Frequencer therapy using a cross-over design.  The sputum weight was the main outcome measure.  Sputum weight was found to be a reproducible measure of the efficacy of chest physiotherapy in individual patients.  The Frequencer induced airway clearance in patients with CF that was equivalent to that of CCPT.  Furthermore, treatment of a 4 % mucin preparation ex-vivo with the Frequencer significantly reduced the viscosity of the mucin solution as determined in a capillary rheometer.  The authors concluded that these results indicated the Frequencer is safe and as effective as CCPT in inducing airway clearance in patients with CF.

Although clinical evidence is limited, high-frequency chest wall oscillation devices have been used for lung transplant recipients who are unable to tolerate standard chest physiotherapy in the post-operative period.

The American Academy of Neurology’s practice parameter update on "The care of the patient with amyotrophic lateral sclerosis" (Miller et al, 2009) noted that "High frequency chest wall oscillation (HFCWO) is unproven for adjunctive airway secretion management".

McIlwaine et al (2013) noted that PEP is the most commonly used method of airway clearance (AC) in Canada for patients with CF whereas, in some countries, HFCWO is the preferred form of AC.  There have been no long-term studies comparing the effectiveness of HFCWO and PEP in the CF population.  These investigators determined the long-term effectiveness of HFCWO compared with PEP mask therapy in the treatment of CF as measured by the number of pulmonary exacerbations (PEs).  A randomized controlled study was performed in 12 CF centers in Canada.  After a 2-month wash-out period, subjects were randomized to perform either HFCWO or PEP mask therapy for 1 year.  A total of 107 subjects were enrolled in the study; 51 were randomized to PEP and 56 to HFCWO.  There were 19 drop-outs within the study period, of which 16 occurred prior to or at the time of randomization.  There were significant differences between the groups in the mean number of PEs (1.14 for PEP versus 2.0 for HFCWO) and time to first PE (220 days for PEP versus 115 days for HFCWO, p = 0.02).  There was no significant difference in lung function, health-related quality of life scores or patient satisfaction scores between the 2 groups.  Positive expiratory pressure mask therapy required a shorter treatment time.  The authors concluded that the results of this study favored PEP and do not support the use of HFCWO as the primary form of AC in patients with CF.

Nolan and colleagues (2014) stated that there are no published guidelines, clinical trials or case series in the management of recalcitrant atelectasis in the infants and toddlers with HFCWO.  These researchers performed a retrospective case-series study of the clinical experience in the management of atelectasis with HFCWO in post-term infants and toddlers.  Subjects included non-cardiac, cardiac, non-pediatric intensive care unit (PICU) and PICU patients.  The HFCWO device used was the SmartVest™ 17-25cm Wrap® (Electromed®, New Prague, MN).  Patients had radiographic evidence of atelectasis not responding to mucolytic therapy (either nebulized 3 % or 7 % hypertonic saline) and conventional chest physiotherapy.  A total of 23 patients with 26 separate admissions with post-term ages of 2 weeks to 17 months were treated; 4 were in the PICU, the others were in general pediatrics.  Atelectasis etiologies were infectious, structural, neurological, post-surgical, congenital defects of the airways and congenital heart disease with compression of bronchi.  The greatest cause of atelectasis was infectious (23, 88 %), rhinovirus being the most common (9, 35 %).  Other causes and co-morbid conditions were: neurologic conditions (6, 23 %), airway anomalies (6, 23 %), and cardiovascular anomalies (3, 11 %).  High-frequency chest wall oscillation was well-tolerated, with only 3 patients (11 %) having documented adverse events consisting of post-tussive emesis (2, 8 %) right after initiation of HFCWO or excessive coughing (1, 4 %).  A combination of 8 Hertz x 10 minutes, then 10 Hertz x 10 minutes at pressure of 15 was the best tolerated setting for the infants and toddlers with 23 (88 %) having these settings.  Patients with viral infectious etiologies consistently had more rapid resolution of the atelectasis (mean of 2 days) than those with structural and/or cardiac anomalies (mean of 9 days).  The authors concluded that HFCWO with a size appropriate device, combined with nebulized 3 % or 7 % saline, for post-term infants and toddlers was well-tolerated and should be considered as a tool for treating recalcitrant atelectasis.  Moreover, they stated that in post-term infants and toddlers with recalcitrant atelectasis, HFCWO, with a size appropriate device, used concurrently with nebulized 3 % or 7 % saline, may be effective therapy.  These investigators stated that clinical randomized trials are needed for comparing HFCWO versus traditional chest percussive therapy in infants and toddlers for managing atelectasis.

Furthermore, and UpToDate review on "Atelectasis in children" (Finder, 2014) does not mention high-frequency chest wall oscillation as a therapeutic option.

StatPearls’ webpage on "Cri du Chat syndrome" (Ajitkumar et al, 2019) did not mention high-frequency chest compression as a therapeutic option for the treatment of Cri du Chat syndrome.  Furthermore, an UpToDate review on "Congenital cytogenetic abnormalities" (Giersch, 2020) does not mention high-frequency chest compression as a management / therapeutic option.

High-Frequency Chest Compression Systems for Rett Syndrome

An UpToDate review on “Rett syndrome: Treatment and prognosis” (Schultz and Glaze, 2021) does not mention high-frequency chest wall oscillation as a management / therapeutic option.

Mechanical Percussors

The purpose of percussion is to apply kinetic energy to the chest wall and lung at regular intervals.  Percussion is also referred to as cupping, clapping, and tapotement.  It can be accomplished by rhythmically striking the thorax with a cupped hand or a mechanical device applied directly over the lung segment(s) being drained.  According to the guidelines developed by American Association for Respiratory Care (AARC) on postural drainage therapy, no convincing evidence demonstrates the superiority of one method over the other; however, use of a mechanical percussor can benefit the patient by allowing for independence and greater compliance.

Flutter and Acapella

The Flutter (Scandipharm, Birmingham, AL) is a handheld pipe-like device with a plastic mouthpiece on one end that the patient exhales into.  On the other end of the pipe, a stainless steel ball rests inside a plastic circular cone.  When the patient exhales into the device, the ball rolls and moves up and down, creating an opening and closing cycle over a conical canal.  The cycle repeats itself many times throughout each exhalation intending to produce oscillations of endobronchial pressure and expiratory airflow that will vibrate the airway walls and loosen mucus so that it can be easily expectorated by the patient.  The Flutter device has 510(k) status with the FDA.  Although the Flutter device has not been shown to significantly change respiratory assessment parameters or pulmonary function, some patients may prefer this method over other therapies.

A similar oscillatory positive airway pressure device, the Acapella (Smiths Medical, Watford, UK), uses a counterweighted plug and magnet to create air flow oscillation.  Volsko et al (2003) noted that the Acapella and Flutter have similar performance characteristics.  The author noted that the Acapella's performance is not gravity-dependent (i.e., dependent on device orientation) and may be easier to use for some patients.

Positive Expiratory Pressure (PEP)

The PEP mask/mouthpiece contains a valve that increases resistance to expiratory airflow.  The patient breathes in and out 5 to 20 times through the flow resistor, creating positive pressure in the airways during exhalation.  The pressure generated can be monitored and adjusted with a manometer.  Either low pressures or high pressures are prescribed.  The PEP mask/mouthpiece achieves the same goal as autogenic drainage (a special breathing technique aimed at avoiding airway compression by reducing positive expiratory transthoracic pressure) by expiring against an external airflow obstruction.

Most studies on the effectiveness of PEP have been conducted in Europe and they reported short-term equivalency of PEP to other methods of airway clearance.  A published review of these studies found that PEP had similar effects on sputum clearance when compared with other methods (postural drainage forced exhalatory technique).  The strongest evidence of the effectiveness of PEP comes from a 1-year randomized controlled clinical trial of PEP versus conventional physiotherapy in 40 children with CF.  The patients treated with PEP showed improvements in pulmonary function, whereas pulmonary function actually declined in patients treated with conventional physiotherapy.  The differences between treatment groups were statistically significant for changes in FVC and forced expiratory volume in 1 second (FEV1).

There are numerous PEP Mask/PEP Valves on the market. Examples include: Resistex PEP Mask (Mercury Medical, Clearwater, FL), TheraPep Valve (DHD Healthcare, Inc., Canastota, NY), Acapella (DHD Healthcare, Inc., Wampsville, NY) and PARI PEP Mask (PARI Respiratory Equipment, Inc., Midlothian, VA).

Intrapulmonary Percussive Ventilator (IPV)

Intrapulmonary Percussive Ventilator (IPV) (Percussionaire Corporation, Sandpoint, ID) is an aerosol machine that delivers a series of pressurized gas minibursts at rates of 100 to 225 cycles/min to the respiratory tract.  Aerosolized medications can be delivered under pressure and with oscillations that vibrate the chest.  In contrast to PEP and flutter, IPV allows continuous monitored positive pressure application and percussion throughout the respiratory cycle.  The patient controls variables such as inspiratory time, peak pressure and delivery rates.  The Percussionaire has 510(k) status with the FDA.

There is a scarcity of scientific data to support the effectiveness of IPV.  A small study (n = 16) by Homnick et al (1995) found IPV as effective as standard aerosol and chest physiotherapy in preserving lung function.  A study by Newhouse et al (1998) concluded that larger and longer studies of IPV compared to standard chest physiotherapy are needed to evaluate its value for independent administration of chest physiotherapy.  Studies do not demonstrate any advantage of IPV over that achieved with good pulmonary care in the hospital environment and there are no studies in the home setting.

Reychler et al (2006) stated that IPV, frequently coupled with a nebulizer, is increasingly used as a physiotherapy technique.  However, its physiological and clinical values have been poorly studied.  These researchers compared lung deposition of amikacin by the nebulizer of the IPV device and that of standard jet nebulization (SJN).  Amikacin was nebulized with both devices in a group of 5 healthy subjects during spontaneous breathing.  The deposition of amikacin was measured by urinary monitoring.  Drug output of both devices was measured.  Respiratory frequency (RF) was significantly lower when comparing the IPV device with SJN (8.2 +/- 1.6 breaths/min versus 12.6 +/- 2.5 breaths/min, p < 0.05).  The total daily amount of amikacin excreted in the urine was significantly lower with IPV than with SJN (0.8 % initial dose versus 5.6 % initial dose, p < 0.001).  Elimination half-life was identical with both devices.  Drug output was lower with IPV than with SJN.  The amount of amikacin delivered to the lung is 6-fold lower with IPV than with SJN, although a lower RF was adopted by the subjects with the IPV.  The authors concluded that the IPV seems unfavorable for the nebulization of antibiotics.

Brückner (2008) stated that assisted coughing and mechanical cough aids compensate for the weak cough flow in patients with neuromuscular diseases (NMD).  In cases with preserved respiratory muscles, breathing techniques and special devices (e.g., Flutter or Acapella) can be used for secretion mobilization during infections of the airways.  These physiotherapeutic approaches were summarized as oscillating physiotherapy.  Their mechanisms are dependent on separation of the mucus from the bronchial wall by vibration, thus facilitating mucus transport from the peripheral to the central airways.  In mucoviscidosis and chronic obstructive pulmonary disease their application is established, but there is a paucity of data regarding the commitment in patients with NMD.  The effective adoption of simple oscillating therapeutic interventions demands usually a sufficient force of the respiratory muscles -- exceptions are the application of the Percussionaire (i.e., IPV) or high-frequency chest wall oscillation (HFCWO).  In daily practice there is evidence that patients with weak respiratory muscles are over-strained with the use of these approaches, or get exhausted.  A general recommendation for the adoption of simple oscillating physiotherapeutic interventions can not be made in patients with NMD.  Perhaps in the future devices such as IPV or HFCWO will prove to be more effective in patients with NMD.

The Impulsator F00012 (Percussionaire Corp, Sandpoint, ID) is an intra-pulmonary percussive ventilator; it is a pneumatic device that delivers high-flow-rate bursts of air and aerosol to the lungs at a frequency of 200 to 300 cycles per minute.  Pulsatile breaths are delivered at a peak pressure of 20 to 40 cm H2O, titrated by visualizing percussive movement of the intercostal spaces.  Breaths are delivered using a mouthpiece, and the lungs percussed for 5- to 15-second intervals over a 15- to 30-min period.  There is a lack of evidence regarding the effectiveness of the Impulsator F00012.

Kallet (2013) stated that mechanically ventilated patients in respiratory failure often require adjunctive therapies to address special needs such as inhaled drug delivery to alleviate airway obstruction, treat pulmonary infection, or stabilize gas exchange, or therapies that enhance pulmonary hygiene.  These therapies generally are supportive in nature rather than curative.  Currently, most lack high-level evidence supporting their routine use.  In this overview, the author described the rationale and examined the evidence supporting adjunctive therapies during mechanical ventilation.  Both mechanistic and clinical research suggests that IPV may enhance pulmonary secretion mobilization and might reverse atelectasis.  However, its impact on outcomes such as ICU stay is uncertain.  The most crucial issue is whether aerosolized antibiotics should be used to treat ventilator-associated pneumonia, particularly when caused by multi-drug resistant pathogens.  There is encouraging evidence from several studies supporting its use, at least in individual cases of pneumonia non-responsive to systemic antibiotic therapy.  Inhaled pulmonary vasodilators provide at least short-term improvement in oxygenation and may be useful in stabilizing pulmonary gas exchange in complex management situations.  Small uncontrolled studies suggest aerosolized heparin with N-acetylcysteine might break down pulmonary casts and relieve airway obstruction in patients with severe inhalation injury.  Similar low-level evidence suggests that heliox is effective in reducing airway pressure and improving ventilation in various forms of lower airway obstruction.  These therapies generally are supportive and may facilitate patient management.  However, because they have not been shown to improve patient outcomes, it behooves clinicians to use these therapies parsimoniously and to monitor their effectiveness carefully.

Branson (2013) stated that postoperative pulmonary complications (PPCs) are common and expensive.  Costs, morbidity, and mortality are higher with PPCs than with cardiac or thromboembolic complications.  Preventing and treating PPCs is a major focus of respiratory therapists, using a wide variety of techniques and devices, including chest physical therapy, continuous positive airway pressure, incentive spirometry, and IPV.  The scientific evidence for these techniques is lacking.

The American Association for Respiratory Care’s clinical practice guideline on "Effectiveness of nonpharmacologic airway clearance therapies in hospitalized patients" (Strickland et al, 2013) listed intrapulmonary percussive ventilation (IPV) as one of the interventions that were considered but not recommended due to insufficient evidence.

Mechanical Insufflation-Exsufflation

Mechanical insufflation-exsufflation (CoughAssist, J.H. Emerson Co., Cambridge, MA) (also known as In-Exsufflator, Cofflator, cough machine) is designed to inflate the lung with positive pressure and assist cough with negative pressure; it is advocated for use in patients with NMD.  The published literature on the effectiveness of mechanical insufflation-exsufflation consists of review articles, case reports, retrospective analyses, and small, uncontrolled case series.  In addition, published research on mechanical insufflation-exsufflation has come from a single investigator, raising questions about the generalization of findings.  A Consensus Panel Report by the American College of Chest Physicians (Irwin et al, 1998) stated that "[t]he inability of patients with respiratory muscle weakness to achieve high lung volumes is likely to contribute to cough ineffectiveness.  Increasing the inhaled volume prior to cough by air-stacking positive pressure breaths or by glossopharyngeal breathing increases cough expiratory flows by 80 % in these patients.  Cough efficiency may be further enhanced by the application of negative pressure to the airway for a period of 1 to 3 s.  Using this technique of mechanical insufflation-exsufflation, peak cough expiratory flows can be increased by more than four-fold."  The Consensus Panel Report, however, concluded that "[w]hile a variety of nonpharmacologic protussive treatment modalities may improve cough mechanics, clinical studies documenting improvement in patient morbidity and mortality are lacking." 

Motivation to perform any airway clearance technique is key to maintaining pulmonary function.  An increase in sputum production, while not necessarily an indicator of improved pulmonary function, motivates most patients to continue with their physiotherapy treatment.  The ease in which the therapy can be performed by a particular patient is another important consideration.  Most adolescent and adult patients who need chest physiotherapy are able to carry out their treatment independently with one of the above methods and using gravity assisted positions and breathing exercises.  Positive expiratory pressure mask/mouthpiece and the Flutter device are well accepted by children.  Long-term comparison of these methods with large groups of patients including the selection of appropriate outcome measures, are needed for further evaluation of the potential success of various methods of airway clearance.

Rose and colleagues (2017) noted that there are various reasons why weaning and extubation failure occur, but ineffective cough and secretion retention can play a significant role.  Cough assist (CA) techniques, such as lung volume recruitment or manually- and mechanically-assisted cough, are used to prevent and manage respiratory complications associated with chronic conditions, particularly neuromuscular disease, and may improve short- and long-term outcomes for people with acute respiratory failure.  However, the role of CA to facilitate extubation and prevent post-extubation respiratory failure is unclear.  In a Cochrane review, these investigators determined extubation success using CA techniques compared to no CA for critically-ill adults and children with acute respiratory failure admitted to a high-intensity care setting capable of managing mechanically-ventilated people (such as an ICU, specialized weaning center, respiratory intermediate care unit, or high-dependency unit).  They also determined the effect of CA techniques on re-intubation, weaning success, mechanical ventilation and weaning duration, length of stay (high-intensity care setting and hospital), pneumonia, tracheostomy placement and tracheostomy de-cannulation, and mortality (high-intensity care setting, hospital, and after hospital discharge). We evaluated harms associated with use of cough augmentation techniques when applied via an artificial airway (or non-invasive mask once extubated/de-cannulated), including hemodynamic compromise, arrhythmias, pneumothorax, hemoptysis, and mucus plugging requiring airway change and the type of person (such as those with neuromuscular disorders or weakness and spinal cord injury) for whom these techniques may be efficacious.  These investigators searched the Cochrane Central Register of Controlled Trials (CENTRAL; Issue 4, 2016), Medline (OvidSP) (1946 to April 2016), Embase (OvidSP) (1980 to April 2016), CINAHL (EBSCOhost) (1982 to April 2016), and ISI Web of Science and Conference Proceedings.  They searched the PROSPERO and Joanna Briggs Institute databases, websites of relevant professional societies, and conference abstracts from five professional society annual congresses (2011 to 2015).  These researchers did not impose language or other restrictions.  They performed a citation search using PubMed and examined reference lists of relevant studies and reviews.  They contacted corresponding authors for details of additional published or unpublished work; and searched for unpublished studies and ongoing trials on the International Clinical Trials Registry Platform (apps.who.int/trialsearch) (April 2016).  These researchers included randomized controlled trials (RCTs) and quasi-RCTS that evaluated CA compared to a control group without this intervention.  They included non-randomized studies for assessment of harms; and included studies of adults and of children aged 4 weeks or older, receiving invasive mechanical ventilation in a high-intensity care setting.  Two review authors independently screened titles and abstracts identified by their search methods; 2 review authors independently evaluated full-text versions, independently extracted data and assessed risks of bias.  They screened 2,686 citations and included 2 trials enrolling 95 participants and 1 cohort study enrolling 17 participants.  These investigators assessed 1 RCT as being at unclear risk of bias, and the other at high risk of bias; they assessed the non-randomized study as being at high risk of bias.  They were unable to pool data due to the small number of studies meeting the inclusion criteria and therefore presented narrative results rather than meta-analyses.  One trial of 75 participants reported that extubation success (defined as no need for re-intubation within 48 hours) was higher in the mechanical insufflation-exsufflation (MI-E) group (82.9 % versus 52.5 %, p < 0.05) (risk ratio (RR) 1.58, 95 % CI: 1.13 to 2.20, very low-quality evidence).  No study reported weaning success or re-intubation as distinct from extubation success.  One trial reported a statistically significant reduction in mechanical ventilation duration favoring MI-E (mean difference -6.1 days, 95 % CI: -8.4 to -3.8, very low-quality evidence).  One trial reported mortality, with no participant dying in either study group.  Adverse events (reported by 2 trials) included 1 participant receiving the MI-E protocol experiencing hemodynamic compromise; 9 (22.5 %) of the control group compared to 2 (6 %) MI-E participants experienced secretion encumbrance with severe hypoxemia requiring re-intubation (RR 0.25, 95 % CI: 0.06 to 1.10).  In the lung volume recruitment trial, 1 participant experienced elevated BP for more than 30 mins.  No participant experienced new-onset arrhythmias, HR increased by more than 25 %, or a pneumothorax.  For outcomes assessed using GRADE, these researchers based their down-grading decisions on unclear risk of bias, inability to assess consistency or publication bias, and uncertainty about the estimate of effect due to the limited number of studies contributing outcome data.  The authors concluded that the overall quality of evidence on the efficacy of CA techniques for critically-ill people was very low; CA techniques when used in mechanically-ventilated critically-ill people appeared to result in few adverse events.

Sanchez-García and associates (2018) stated that catheter suctioning of respiratory secretions in intubated subjects is limited to the proximal airway and associated with traumatic lesions to the mucosa and poor tolerance; MI-E exerts positive pressure, followed by an abrupt drop to negative pressure.  Potential advantages of this technique are aspiration of distal airway secretions, avoiding trauma, and improving tolerance.  These researchers applied insufflation of 50 cmH2O for 3 seconds and exsufflation of - 45 cmH2O for 4 seconds in patients with an endotracheal tube or tracheostomy cannula requiring secretion suctioning.  Cycles of 10 to 12 insufflations-exsufflations were performed and repeated if secretions were aspirated and visible in the proximal artificial airway.  Clinical and laboratory parameters were collected before and 5 and 60 minutes after the procedure.  Subjects were followed during their ICU stay until discharge or death; MI-E was applied 26 times to 7 men and 6 women requiring suctioning.  Mean age was 62.6 ± 20 years and mean Apache II score 23.3 ± 7.4 points.  At each session, a median of 2 (inter-quartile range [IQR] 1; 2) cycles on median day of intubation 11.5 (IQR 6.25; 25.75) were performed.  Mean insufflation tidal volume was 1,043.6 ± 649.9 ml.  No statistically significant differences were identified between baseline and post-procedure time-points.  Barotrauma, desaturation, atelectasis, hemoptysis, or other airway complication and hemodynamic complications were not detected.  All, except one, of the MI-E sessions, were productive, showing secretions in the proximal artificial airway, and were well-tolerated.  The authors concluded that these preliminary findings suggested that MI-E may be safe and effective in patients with artificial airway.  They stated that the safety and efficacy of this approach need to be confirmed in larger studies over a broader range of severity.

The authors stated that the main drawbacks of this study were the small sample size (n = 13) and the relative clinical stability of most patients, thus preventing these investigators from drawing conclusions for patients in higher severity groups, like those with acute respiratory distress syndrome or severe hemodynamic dysfunction.  Furthermore, not being a controlled study, the observed safety and efficacy data need to be further evaluated in future randomized controlled trials.

Coutinho and colleagues (2018) noted that CA is a device to improve bronchial hygiene of patients with secretion in the airways and ineffective cough.  In a randomized, cross-over study, these investigators compared the physiological effects and the volume of secretion of MI-E (CA device) with isolated endotracheal suctioning in mechanically ventilated patients.  The patients were randomly allocated to the first technique, then the following technique was performed in the next day.  These researchers collected the variables related to oxygen saturation, hemodynamics (HR, systolic BP, diastolic BP, and mean arterial pressure [MAP]), and respiratory mechanics (tidal volume, minute volume, respiratory rate, and lung compliance and resistance), pre- and post-implementation (immediately and after 15 and 30 mins), and the aspirated volume of secretion.  They used 2-way analysis of variance (ANOVA) followed by the Student-Newman-Keuls t-test to compare the variables at different time-points.  Student's t-test was used to compare secretion volumes.  All data were stored and analyzed in SPSS for Windows Version 19.0; the significance level was set at 5 %.  A total of 43 patients were included in the study.  When these researchers compared the results before and after the application of the techniques, they observed no significant difference in lung compliance, pulmonary resistance, MAP, peripheral oxygen saturation, and secretion volume in both groups.  The authors concluded that MI-E performed with a CA device did not alter respiratory or hemodynamic stability when compared to conventional tracheal suctioning, but also failed to reduce the volume of secretion.  Moreover, they stated that further studies with different protocols and sample sizes are needed to demonstrate the possible superiority of MI-E over other bronchial hygiene techniques or its effectiveness as an isolated method.

de Camillis and co-workers (2018) stated that few studies have evaluated the effects of MI-E in subjects on mechanical ventilation.  In a randomized, parallel-group, open-label study, these researchers evaluated the effectiveness of MI-E on airway mucus clearance among mechanically ventilated ICU subjects.  The trial was conducted between June and November 2017 in a single, mixed ICU.  Adult ICU subjects receiving mechanical ventilation for more than 24 hours with stable ventilatory and hemodynamic status were randomized to receive either standard respiratory physiotherapy alone (control group) or respiratory physiotherapy by using an MI-E device (intervention group).  The primary outcome was the weight of aspirated airway mucus after study interventions.  Secondary outcomes included variation in static lung compliance (ΔCL), airway resistance (ΔRaw), work of breathing (ΔWOB) in relation to the pre-intervention period, and hemodynamic and ventilator complications during the procedures.  There were 90 subjects in each group.  The mean ± SD weight of the aspirated airway mucus was higher in the intervention group than in the control group (2.42 ± 2.32 g versus 1.35 ± 1.56 g, p < 0.001).  The ΔCL values in the intervention group were higher than those in the control group (1.76 ± 4.90 ml/cm H2O versus -0.57 ± 4.85 ml/cm H2O, p = 0.001).  The ΔRaw and ΔWOB values were similar between the groups.  No hemodynamic or ventilatory complications were observed.  The authors concluded that among the general ICU subjects receiving mechanical ventilation, use of an MI-E device during respiratory physiotherapy resulted in a larger amount of airway mucus clearance than respiratory physiotherapy alone.

Continuous High-Frequency Oscillation Therapy

Morgan and colleagues (2016) noted that continuous high-frequency oscillation (CHFO) creates a pressure gradient in the small airways that accelerates expiratory flow.  The intended use of CHFO therapy is to facilitate secretion removal and treat atelectasis.  These researchers evaluated the feasibility, safety, and effectiveness of CHFO in the mechanically ventilated pediatric population.  After institutional review board approval, these investigators retrospectively reviewed medical records of mechanically ventilated children treated with CHFO (the MetaNeb system) at their institution from July 1, 2007 through August 31, 2012.  Patients supported with extracorporeal membrane oxygenation were excluded.  The authors evaluated changes in ventilator settings in subjects with ventilator data documented within 6 hours pre- and post-treatment.  They evaluated arterial blood gas (ABG) results for individual treatments, comparing ABG results within 8 hours pre-therapy to ABG results within 3 hours post-treatment.  Oxygen index and PaO2 /FIO2 were calculated.  Demographic data, blood pressure (BP), heart rate (HR), and development of new air leak while being treated with CHFO were recorded.  Pre- and post-CHFO measurements were compared using Wilcoxon signed-rank testing.  This cohort included 59 invasively ventilated subjects.  Median age was 2 years (range of 1 month to 19 years), and median weight was 14 kg (2 to 81 kg).  These researchers evaluated data on 528 total treatments (range per subject 1 to 39 treatments).  Peak inspiratory pressure significantly decreased with CHFO, whereas other parameters, including PaCO2 and breathing frequency, remained stable.  There was no significant change in systolic BP, diastolic BP, or HR following treatment with CHFO.  One subject (2 %) developed a clinically insignificant pneumothorax during CHFO.  The authors concluded that CHFO is feasible and appears safe in this cohort of mechanically ventilated pediatric subjects.  The rate of pneumothorax was consistent with that seen in similar pediatric ICU populations.  They stated that these preliminary results suggested that CHFO may be beneficial by improving lung compliance in pediatric subjects with secretion-induced atelectasis; prospective clinical studies are needed to further evaluate the clinical safety and effectiveness of CHFO in children receiving invasive mechanical ventilation.

Malakian and associates (2020) stated that respiratory distress syndrome (RDS) is one of the main causes of mortality in premature neonates.  Treatment of these neonates with invasive mechanical ventilation has side effects such as chronic pulmonary diseases.  Non-invasive ventilation, such as nasal continuous positive airway pressure (NCPAP) and nasal high-frequency oscillation ventilation (nHFOV), has shown to reduce the burden of chronic lung disease.  These investigators stated that nHFOV is a promising new mode of non-invasive ventilation and may reduce the need for mechanical ventilation and reduce possible complications.  In a RCT, these researchers hypothesized that early nHFOV would reduce the need for invasive respiratory support in comparison to NCPAP in preterm neonates with RDS.  A total of 124 neonates between 28 to 34 weeks of gestational age (GA) with RDS hospitalized at Imam Khomeini Hospital, Ahvaz in 2016 were included in this study.  The primary outcomes were the failure of nHFOV and NCPAP within 72 hours after birth; secondary outcome were the duration of invasive ventilation and possible side effects.  Of the 124 neonates, 63 and 61 were studied in the nHFOV and NCPAP groups, respectively.  There were no significant differences between nHFOV (6.5 %) and NCPAP (14.1 %) groups in terms of rates of primary consequences (p = 0.13).  However, the duration of non-invasive ventilation in nHFOV was significantly less than that of NCPAP group (p = 0.01).  The authors concluded that in preterm infants from 28 to 34 weeks of GA, nHFOV did not reduce the need for mechanical ventilation during the first 72 hours following birth compared to NCPAP; however, the duration of non-invasive ventilation in the NHFOV group was significantly shorter.

Iranpour and colleagues (2019) noted that currently, various forms of non-invasive respiratory support have been used in the management of RDS in preterm neonates.  However, nHFOV has not yet been applied commonly as an initial treatment.  In a randomized clinical trial, these investigators examined the safety and efficacy of nHFOV compared with NCPAP in preterm and near-term infants with RDS.  A total of 68 neonates (GA between 30 and 36 weeks and 6 days) with a clinical diagnosis of RDS were randomly assigned to either the NCPAP (n = 34) or the nHFOV (n = 34) group.  The primary outcome was the duration of non-invasive respiratory support (duration of using NCPAP or nHFOV).  The median (IQR) duration of non-invasive respiratory support, was significantly shorter in the nHFOV group than that in the NCPAP group (20 (15 to 25.3) hours versus 26.5 (15 to 37.4) hours, respectively; p = 0.02).  The need for a ventilator occurred in 4 out of 34 (11.8 %) neonates in the NCPAP group and in none of the neonates in the nHFOV group (p = 0.03).  In addition, intra-ventricular hemorrhage (IVH) occurred in 9 cases (6.9 %) in the NCPAP group and 2 cases (3.3 %) in the nHFOV group, which showed a significant difference (p = 0.04).  The incidence of pneumothorax, chronic lung disease, pulmonary hemorrhage and necrotizing enterocolitis was similar between the 2 groups.  The authors concluded that the findings of this study showed that nHFOV significantly reduced the duration of non-invasive respiratory support and decreased the need for intubation compared with NCPAP in infants with RDS.  Furthermore, nHFOV appeared to reduce the incidence of IVH without increasing other complications.  Moreover, these researchers stated that to suggest the routine use of nHFOV as an initial therapy in the management of preterm neonates, further studies, especially multi-center trials, are needed.

The authors stated that this study had several drawbacks.  First, the number of subjectss in this study was small (n = 34 in each of the 2 groups), and although the findings were significant, they should be taken with caution.  For routine and widespread use of nHFOV as a primary mode of respiratory support in premature neonates with RDS, more studies are needed.  Second, due to a lack of sufficient facilities and financial constraints, some premature neonates were eligible for this trial, but these researchers could not include them all, as they did not have enough ventilators for nHFOV.

High-Flow Nasal Cannula Therapy

Nishimura (2016) noted that high-flow nasal cannula (HFNC) oxygen therapy is performed by means of an air/oxygen blender, active humidifier, single heated tube, and nasal cannula.  Being able to deliver adequately heated and humidified medical gas at flows up to 60 L/min, it is considered to have a number of physiological advantages compared with other standard oxygen therapies, including reduced anatomical dead space, positive end-expiratory pressure (PEEP), constant F(IO2), and good humidification.  Although few large randomized clinical trials have been performed, HFNC has been gaining attention as an alternative respiratory support for critically ill patients.  Published data are mostly available for neonates.  For critically ill adults, however, evidence is uneven because the reports cover various subjects with diverse underlying conditions, such as hypoxemic respiratory failure, exacerbation of COPD, post-extubation, pre-intubation oxygenation, sleep apnea, acute heart failure, and conditions entailing do-not-intubate orders.  Even so, across the diversity, many published reports suggested that HFNC decreases breathing frequency and work of breathing and reduced the need for respiratory support escalation.  The author stated that some important issues remain to be resolved, such as definitive indications for HFNC and criteria for timing the starting and stopping of HFNC and for escalating treatment.

Zhang and associates (2016) stated that HFNC oxygen therapy has several physiological advantages over traditional oxygen therapy devices, including decreased nasopharyngeal resistance, washing out of the nasopharyngeal dead space, generation of positive pressure in the pharynx, increasing alveolar recruitment in the lungs, humidification of the airways, increased fraction of inspired oxygen and improved muco-ciliary clearance.  Recently, the use of HFNC in treating adult critical illness patients has significantly increased, and it is now being used in many patients with a range of different disease conditions.  However, there are no established guidelines to direct the safe and effective use of HFNC for these patients.  These researchers summarized the available published literature on the positive physiological effects, mechanisms of action, and the clinical applications of HFNC, compared with traditional oxygen therapy devices.  The authors concluded that the available literature suggested that HFNC oxygen therapy is an effective modality for the early treatment of critically adult patients.  Moreover, they stated that further research is needed to confirm the long-term effects of HFNC and identify the adult patient population(s) to whom it could be most beneficial.

The authors stated that HFNC had several drawbacks:

1. expense and complexity (air/O2 blender, humidifier and requirement for a large oxygen supply),
2. mobility (limited ambulation),
3. leak mitigating positive airway pressure effect and inability to compensate for leaks,
4. nasopharyngeal airway pressure and PEEP warrant more exploration,
5. potential for delayed intubation, and
6. potential for (inappropriate) delay of end-of-life decisions.

Nedel and colleagues (2017) stated that HFNC oxygen delivery has been gaining attention as an alternative means of respiratory support for critically ill patients, with recent studies suggesting equivalent outcomes when compared with other forms of oxygen therapy delivery.  These investigators extracted current data regarding the effectiveness of HFNC in critically ill subjects with or at risk for respiratory failure.  They performed a systematic review of publications (from database inception to October 2015) that evaluated HFNC in critically ill subjects with or at risk for acute respiratory failure and performed a meta-analysis comparing HFNC with non-invasive ventilation (NIV) and with standard oxygen therapy regarding major outcomes: incidence of invasive mechanical ventilation and ICU mortality.  A total of 9 studies were included.  HFNC was not associated with a reduction in the incidence of invasive mechanical ventilation compared with NIV (odds ratio [OR] 0.83, 95 % confidence interval [CI]: 0.57 to 1.20, p = 0.31) or standard oxygen therapy (OR 0.49, 95 % CI: 0.22 to 1.08, p = 0.17).  Additionally, HFNC use did not reduce ICU mortality compared with NIV (OR 0.72, 95 % CI: 0.23 to 2.21, p = 0.56) or with standard oxygen therapy (OR 0.69, 95 % CI: 0.33 to 1.42, p = 0.29).  There was a trend toward better oxygenation compared with conventional oxygen therapy but a worse gas exchange compared with NIV.  The authors concluded that HFNC therapy appeared not to be superior to conventional oxygen therapy or NIV in terms of invasive mechanical ventilation rate or ICU mortality in critical illness, but new studies are needed to examine if HFNC is associated with any difference in major outcomes when compared with other techniques.

Individuals with Acute Pneumonic Respiratory Failure Receiving Mechanical Ventilation

Chuang and colleagues (2017) stated that endotracheal intubation and prolonged immobilization of patients receiving mechanical ventilation may reduce expectoration function.  High-frequency chest wall oscillation (HFCWO) may ameliorate airway secretion movement; however, the instantaneous changes in patients' cardiopulmonary responses are unknown.  Moreover, HFCWO may influence ventilator settings by the vigorous oscillation.  These researchers investigated these issues.  A total of 73 patients (52 men) aged 71.5 ± 13.4 years who were intubated with mechanical ventilation for pneumonic respiratory failure were recruited and randomly classified into 2 groups (HFCWO group, n = 36; and control group who received conventional chest physical therapy (CCPT, n = 37).  HFCWO was applied with a fixed protocol, whereas CCPT was conducted using standard protocols.  Both groups received sputum suction after the procedure.  Changes in ventilator settings and the subjects' responses were measured at pre-set intervals and compared within groups and between groups.  Oscillation did not affect the ventilator settings (all p > 0.05).  The mean airway pressure, breathing frequency, and rapid shallow breathing index increased, and the tidal volume and SpO2 decreased (all p < 0.05).  After sputum suction, the peak airway pressure (Ppeak) and minute ventilation decreased (all p < 0.05).  The HFCWO group had a lower tidal volume and SpO2 at the end of oscillation, and lower Ppeak and tidal volume after sputum suction than the CCPT group.  The authors concluded that HFCWO affected breathing pattern and SpO2 but not ventilator settings, whereas CCPT maintained a steadier condition.  After sputum suction, HFCWO slightly improved Ppeak compared to CCPT, suggesting that the study extends the indications of HFCWO for patients with acute pneumonic respiratory failure in ICU.

The authors stated that this study had several drawbacks:

1. although this is a randomized controlled study, there was still enrollment bias.  Despite more subjects receiving sedation in the CCPT group than in the HFCWO group, the CCPT group was sedated to a shallower level.  However, the entire CCPT group had poorer consciousness because some of them had lower levels of consciousness because of underlying illness despite receiving less sedation.  The poorer consciousness might be the main cause of a steadier cardiopulmonary response during the procedures in the CCPT group than in the HFCWO group.  However, Ppeak was lower in the HFCWO group than in the CCPT group after sputum suction, suggesting that sedation use or consciousness level did not affect the main results of the study,
2. patients were intended to use ventilator on pressure control mode.  However, 2 patients of the HFCWO group were used volume control mode.  Intent-to-treat analysis was used in this study.  Thus, the 2 patients were not excluded from analysis,
3. this study showed that HFCWO can be safe, but CCPT appeared more effective for tidal volume before and after sputum suction.  However, the changes (Δ) in tidal volume between baseline and after sputum suction for 15 minutes were not significant in either group, suggesting a larger scale of patient population for this regard is warranted,
4. another selection bias was a concern that Ppeak was higher at baseline so that Ppeak might be higher at 15 minutes after sputum suction in the CCPT group than the HFCWO group.  However, the difference between groups in ΔPpeak between baseline and recovery from sputum suction for 15 minutes was larger in HFCWO group than in CCPT group.  Mortality rate was higher in the CCPT group than the HFCWO.  This might also be attributed to selection bias as the incidence of multi-organ failure tended to be higher in the CCPT group than in the HFCWO group, although insignificantly.  The hospital stay, lung function, or BODE score (a multi-dimensional 10-point scale for evaluation of chronic obstructive pulmonary disease) was not reported, as these were not the foci of the study, and
5. this was an observational study exploring many variables, there was a potential risk of finding statistically significant association because of chance.

The Volara System Oscillation & Lung Expansion (OLE) Therapy Device

The Volara System Oscillation & Lung Expansion (OLE) therapy device combines 3 respiratory therapies in a single device.  It provides continuous positive expiratory pressure (CPEP) to expand the patient’s lungs and airways, continuous high-frequency oscillation (CHFO) pulses to dislodge mucus; thus, making it easier to cough out, and nebulized medication to relax the patient’s airways and aid in breathing with less effort.  There is a lack of evidence to support the effectiveness of the Volara System in improving health outcomes.

Huynh and colleagues (2019) noted that post-operative pulmonary complications (PPCs) cause high morbidity and mortality.  Targeted treatment for patients at risk for PPCs could improve outcomes.  In a prospective, multi-center trial, these researchers examined the impact of OLE therapy, using CHFO and CPEP on PPCs in high-risk patients.  In stage I, CPT and ICD codes were queried for patients (n = 210) undergoing thoracic, upper abdominal, or aortic open procedures at 3 institutions from December 2014 to April 2016.  Patients were selected randomly.  Age, co-morbidities, American Society of Anesthesiologists (ASA) physical status classification scores, and PPC rates were determined.  In stage II, a total of 209 subjects were enrolled prospectively from October 2016 to July 2017 using the same criteria.  Stage II subjects received OLE treatment and standard respiratory care.  The PPCs rate (prolonged ventilation, high-level respiratory support, pneumonia, intensive care unit [ICU] re-admission) were compared.  These investigators also compared ICU length of stay (LOS), hospital LOS, and mortality using t-tests and analysis of co-variance.  Data were presented as mean ± SD.  There were 419 subjects.  Stage II patients were older (61.1 ± 13.7 years versus 57.4 ± 15.5 years; p < 0.05) and had higher ASA scores.  Treatment with OLE decreased PPCs from 22.9 % (stage I) to 15.8 % (stage II) (p < 0.01 adjusted for age, ASA score, and operation time).  Similarly, OLE treatment reduced ventilator time (23.7 ± 107.5 hours to 8.5 ± 27.5 hours; p < 0.05) and hospital LOS (8.4 ± 7.9 days to 6.8 ± 5.0 days; p < 0.05).  No differences in ICU LOS, pneumonia, or mortality were observed.  The authors concluded that the findings of this study suggested that the modality is feasible and could aid in achieving value-based quality care for surgical patients.  Furthermore, other disease entities with a high likelihood of pulmonary complications should be considered for future OLE studies, including those admitted following blunt chest trauma, COPD exacerbation, cystic fibrosis, and pneumonia.

Furthermore, UpToDate reviews on “Cystic fibrosis: Management of advanced lung disease” (Simon, 2021a), “Cystic fibrosis: Overview of the treatment of lung disease” (Simon, 2021b), and “Cystic fibrosis: Treatment of acute pulmonary exacerbations” (Simon, 2021c) do not mention oscillation and lung expansion therapy as a management / therapeutic option.

Caldwell et al (2020) noted that the MetaNeb System is a respiratory therapy modality that aims to effect clearance of airway secretions through chest physiotherapy.  It is usually employed in critically ill patients with bronchiectasis or copious secretions.  However, it also expands lungs through a continuous positive expiratory pressure (PEP) and continuous high-frequency oscillation, which has the benefit of increasing lung recruitment and improving oxygenation.  In a case-report, these investigators described the case of a 61-year-old man who had re-expansion pulmonary edema following a paracentesis and thoracentesis for cirrhosis, which caused a large unilateral pleural effusion.  He required intubation and his hypoxemia was refractory to standard maximum ventilatory measures.  A trial of continuous MetaNeb acted as a non-invasive extracorporeal membrane oxygenation (ECMO) method, dramatically improving oxygenation and hypoxemia, normalizing the patient's blood gas; thereby, stabilizing him.  The authors concluded that MetaNeb could potentially be used in other community hospitals that lack the capability for advanced ventilatory modes or in patients who are too unstable for transfer.  Moreover, these researchers stated that further investigation is needed to examine the potential of the MetaNeb System as an adjunct therapy for critically ill patients on mechanical ventilation and refractory hypoxemia due to alveolar gas mismatch.

There is a clinical trial entitled “Oscillation and Lung Expansion Therapy in Patients With COVID-19” that is currently recruiting subjects; this study is sponsored by Hill-Rom, and the intervention device is the MetaNeb System.  This pilot study is designed to examine the impact of Oscillation and Lung Expansion (OLE) therapy using the MetaNeb System on the hospital length of stay (LOS) in patients hospitalized and receiving heated high-flow oxygen therapy for COVID-19 infection (last updated: May 10, 2022).  

Furthermore, there is a clinical trial entitled “Oscillation and Lung Expansion (OLE) for Treatment of Neuromuscular Disease Patients” that is currently recruiting subjects; this study is sponsored Hill-Rom.  The primary objective of this trial is to examine the impact of OLE for the treatment of respiratory complications of neuromuscular disease patients (last updated: May 9, 2022). 

High-Frequency Chest Compression Systems for Dyspnea in COPD

Daynes et al (2022) noted that chronic obstructive pulmonary disease (COPD) is characterized by symptomatic dyspnea and reduced exercise tolerance, in part as a result muscle weakness, for which inspiratory muscle training (IMT) may be useful.  Excess mucus hyper-secretion commonly co-exists in COPD and may lead to reduce ventilation, further impacting on breathlessness.  Devices for sputum clearance may be employed to aid mucus expectoration.  In a randomized, double-blind, sham-controlled trial, these researchers examined the effectiveness of a combined IMT and high-frequency airway oscillating (HFAO) device in the management of dyspnea; this study recruited symptomatic patients with COPD.  Patients were randomized to either a HFAO device (Aerosure) or sham device for 8 weeks, 3 times a day.  The primary outcome was the Chronic Respiratory Questionnaire dyspnea (CRQ-D) domain.  Pre-specified subgroup analyses were carried out including those with respiratory muscle weakness, excessive sputum and frequent exacerbators.  A total of 104 subject (68 % men, mean (SD) age of 69.75 years (7.41), FEV1 per cent predicted 48.22 % (18.75)) were recruited to this study with 96 participants completing.  No difference in CRQ-D was observed between groups (0.28, 95 % CI: -0.19 to 0.75, p = 0.24), though meaningful improvements were observed over time in both groups (mean (SD) HFAO 0.45 (0.78), p < 0.01; sham 0.73 (1.09), p < 0.01).  Maximal inspiratory pressure significantly improved in the HFAO group over sham (5.26, 95 % CI: 0.34 to 10.19, p = 0.05).  Similar patterns were observed in the subgroup analysis.  The authors concluded that there were no statistical differences between the HFAO and the sham group in improving dyspnea measured by the CRQ-D.

High-Frequency Chest Compression Systems for Plastic Bronchitis

An UpToDate review on “Management of complications in patients with Fontan circulation” (Johnson and Connolly, 2022) states that “Plastic bronchitis is estimated to occur in 3 to 4 % of patients after Fontan procedure and is associated with similar risk factors as protein-losing enteropathy (PLE).  In plastic bronchitis, there is formation of mucofibrinous bronchial casts, resulting in marked airway obstruction.  Patients will often expectorate these large casts or require urgent removal by bronchoscopy, and life-threatening events may occur in up to 40 % of affected patients.  Initial management of patients with active plastic bronchitis is similar to that of PLE, including optimization of Fontan hemodynamics and ensuring there is no alternate reversible cause of elevated central venous pressure.  Proposed treatment options include inhaled or systemic steroids, aerosolized mucolytics, and aerosolized fibrinolytics such as tissue plasminogen activator.  There are limited available data on survival; a study of 25 patients reported a median transplant-free survival of 8.3 years after diagnosis”.  VEST Airway Clearance System is not mentioned as a management option.

Simeox Bronchial Drainage Device

Schmidt et al (2022) noted that in CF airways, impaired airway muco-ciliary clearance and mucus accumulation due to CF transmembrane conductance regulator defects contribute to inflammation, progressive structural lung damage, and decline of lung function.  Physiotherapy is essential to promote mucus mobilization and removal in CF and is a key element of rehabilitation measures; however, conventional techniques may be suboptimal to mobilize viscous mucus.  In a prospective, clinical cohort, single-center study, these investigators examined the specific effects of a novel bronchial drainage device (BDD) (Simeox, PhysioAssist) in subjects with CF and assessed lung function, diaphragm mobility, and sputum properties. Simeox technology is reported to mobilize and transport mucus from the distal tracts by disseminating a vibratory pneumatic signal in the bronchial tree during exhalation. This trial was carried out in the setting of outpatient physiotherapy.  These researchers examined CF patients (n = 21) with stable CF lung disease and collected pulmonary lung function tests (PFT), diaphragm mobility, and sputum properties before and after 2 physiotherapy sessions using the novel BDD.  PFT was evaluated using spirometry and diaphragm mobility using m-mode ultrasound (US) analysis.  Spontaneous sputum samples were collected before and after using the BDD and analyzed for microstructure and DNA concentrations.  PFT parameters (FEV1, FVC, mean expiratory flow at 25 %, 50 %, and 75 % of vital capacity [MEF25/50/75]) were not affected by the use of the BDD.  US analysis of diaphragm mobility revealed an increase in maximum diaphragm excursion upon the intervention.  Mucus analysis demonstrated altered microstructure and higher DNA concentrations collected after using the BDD compared to samples collected before.  Pearson correlation analysis showed significant correlations between changes in mucus properties and DNA levels in respective mucus samples.  The authors concluded that the findings of this study showed that the novel BDD improved diaphragm mobility and altered sputum properties in subjects with CF.  These researchers stated that this novel BDD with unique properties should be further examined in CF‐specific physiotherapy and could complement the physiotherapy methods for CF patients suffering from severe mucus retention. These investigators stated that this study had 2 main drawbacks.  Since this was a pilot study to examine the basic effects of the BDD, the study design was mono-centric; and a relatively low number of cases (n = 21) was targeted.

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References