Review Articles

The recent medical literature includes a large number of review articles concerning the pathophysiology of mucociliary clearance mechanisms, diseases and conditions associated with impaired secretion clearance, descriptions and discussions of the array of modalities available for managing airway clearance and recommendations for their use.

  1. App EM, Wunderlich MO, Lohse P, King M, Matthys H. Oscillatory physiotherapy for bronchial diseases: rheological and anti-inflammatory effects. Pneumologie 1999; 53:348-359.
    This article reviews the rheologic and inflammatory sequelae of chronic lung disease. A discussion of the mycolytic effects of oscillatory physiotherapy on bronchial secretions is followed by an overview of several oral high frequency (OHF) and high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) oscillatory devices, their mechanisms of action and their usefulness.
  2. Barker AF. Bronchiectasis. N Engl J Med 2002 May; 346 (18): 1383-1393.
    This comprehensive review of bronchiectasis discusses its diverse etiologies, pathophysiology, clinical course and treatment. Diagnosis is made on the basis of chronic daily production of mucopurulent sputum and compatible findings on high resolution computed tomography (HRCT). In the discussion of the role of airway clearance therapy, the author states that, “Enhancing the removal of bronchial secretions in bronchiectasis has been shown to be useful…Traditional chest clapping or cupping has largely been replaced by the use of inflatable vests [i.e. high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO)] or mechanical vibrators applied to the chest.”
  3. Chiappetta A, Davis S. Airway clearance practices of respiratory care practitioners, physical therapists and physiotherapists from CF centers. Pediatr Pulmonol 1996 ;( suppl 13):A353.
    To establish guidelines to inform selection of patient-appropriate airway clearance modalities, a questionnaire was distributed to respiratory care practitioners, physical therapists, and physiotherapists attending the Ninth Annual North American CF Conference (1995). This review summarizes comments of 64 respondents concerning airway clearance technique recommendations prevalent at their center of practice, protocols used for monitoring efficacy, and patient criteria for choice of therapy.
  4. Dodd ME, Prasad SA. Physiotherapy management of cystic fibrosis. Chron Respir Dis 2005; 2: 139-149. Routine airway clearance therapy (ACT) has become a standard care practice for patients with cystic fibrosis (CF). Its current status is based on better understanding of CF pathophysiology and on observations of improved health and longevity associated with ACT. This review considers, among other topics, the evidence for and current practice of airway clearance, the array of available ACT techniques and devices, and the importance of therapies that promote independence and disease self-management.
  5. Dosman CF, Jones RL. High-frequency chest compression: a summary of the literature. Can Respir J. 2005; 12:37-41.
    This review of selected high frequency chest compression (HFCC) literature describes the history of the technology and summarizes studies of its effects on mucus transport, pulmonary function, end-expiratory lung volume and quality of life. Several studies show that HFCC provides better mucus clearance and better lung function compared with conventional chest physiotherapy (CPT).
  6. Fink JB, Mahlmeister MJ. High-frequency oscillation of the airway and chest wall. Respir Care 2002; 47 (7): 797-807.
    This paper reviews a growing body of basic research and clinical study evidence supporting the use of airway clearance modalities that create high frequency oscillations in the airways to promote secretion clearance. The mechanisms of action and use of several devices are discussed, including the relatively simple oral devices – Flutter, Acapella – and the more complex equipment designed to provide high-frequency chest wall compression (HFCC)/high frequency chest wall oscillation (HFCWO) and intrapulmonary percussive ventilation (IPV). Device types are differentiated by characterization of airflow patterns and airway and esophageal pressures.
  7. George RJ, Geddes DM. High frequency oscillations and mucociliary transport. Biomed Pharmacother. 1989; 43:25-30.
    This article reviews early in vitro, animal, and human subjects’ studies demonstrating the mucokinetic effects of high frequency oscillation of air within the lungs; it concludes that robust evidence supports the technique as a means of improving the clearance of secretions from the lung.
  8. Hardy KA, Anderson BD. Noninvasive clearance of airway secretions. Respir Care Clin N Am 1996; 2:323-45.
    This review article by a pediatric pulmonologist stresses that airway clearance techniques (ACT) should be considered for any patient who has a disease known to alter mucus clearance. Examples include cystic fibrosis (CF), dyskinetic cilia syndromes, and bronchiectasis from any cause. Patients with atelectasis from mucus plugs and hypersecretory states, such as asthma and chronic bronchitis, patients with pain secondary to surgical procedures, and patients with neuromuscular disease, weak cough, and abnormal patency of the airway may also benefit from the application of airway clearance techniques. The appropriate use, advantages and disadvantages of and array of ACTs, including high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) is discussed.
  9. Hess DR. The evidence for secretion clearance techniques. Respir Care 2001; 46:1276-1292.
    Review In this near-comprensive (2001) review of evidence for various airway clearance techniques, a leading authority on the subject evaluates the quality of clinical studies involving: chest physiotherapy (CPT), postural drainage (PD), forced expiratory technique (FET), autogenic drainage (AD), high-frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO), flutter device, positive expiratory pressure (PEP), intrapulmonary percussion and mechanical in-exsufflation. Most of the studies identified were small, most used crossover designs, and few used sham therapy; many were limited to short-term outcomes such as sputum clearance with a single treatment session. The need for better quality, longer-term studies is discussed.
  10. Langenderfer B. Alternatives to percussion and postural drainage. A review of mucus clearance therapies: percussion and postural drainage, autogenic drainage, positive expiratory pressure, flutter valve, intrapulmonary percussive ventilation, and high-frequency chest compression with the ThAIRapy Vest. J Cardipulmonary Rehabil 1998; 18:283-289.
    This review of published studies on the efficacy of old and new mucus clearance techniques is intended to inform recommendations for different groups of patients. The theoretical basis, mechanisms of action, usage techniques and advantages and disadvantages of available airway clearance modalities are discussed in detail. High frequency chest compression (HFCC) is described as a device that, “…provide[s] mucus clearance assistance to patients who lack the ability to perform the simpler techniques… [and] promote[s] independence and self-care in the patient…”
  11. Marshall BC, Samuelson WM. Basic therapies in cystic fibrosis; Does standard therapy work? Clin Chest Med 1998; 19 (3): 487-504.
    This article focuses on treatment of cystic fibrosis (CF) pulmonary disease and includes a discussion of the following specific components of a standard therapeutic approach to CF: (1) antibiotics, (2) airway clearance and exercise, (3) mucolytics, (4) bronchodilators, (5) oxygen, (6) anti-inflammatory therapies, and (7) nutritional support. The role of high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) as an airway clearance modality is summarized: [HFCC/HFCWO] “…therapy is delivered to the entire chest at the same time, with the patient in a seated position. This allows the administration of nebulized medications during the therapy session, minimizing the patient’s time commitment, but the major advantage over conventional chest physiotherapy is the degree of independence afforded the patient.”
  12. Oberwaldner B. Physiotherapy for airway clearance in paediatrics. Eur J Respir Care 2000; 15 (1): 196-204.
    The basic therapeutic principles in pediatric chest physiotherapy (CPT) are identical to those applied in adults, but child growth and development correspond to continuing changes in respiratory structure and function. For these reasons, airway clearance techniques (ACT) must be adapted to accommodate complex physiological – as well as cognitive –differences. This review provides a detailed discussion of characteristics of the developing lung, chest wall, and airways, making clear that those differences among infant, child and adult demand careful analysis of the available mucus clearance techniques. Particular emphasis is placed upon hazards associated with improperly modified chest physiotherapy (CPT).
  13. Prasad A, Esta-Lee T, Mikelsons C. Physiotherapy in cystic fibrosis. J R Soc Med 2000 ;( suppl 38):93, 27-36.
    This review of current (2000) clinical opinion concerning the efficacy of various airway clearance techniques in patients with chronic lung disease considers active cycle breathing techniques (ACBT), exercise, high-frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) intrapulmonary percussive ventilation (IPV), and the Flutter® valve.
  14. Pryor JA. Physiotherapy for airway clearance in adults. Eur Respir J 1999; 14:1418-1424.
    This review of airway clearance techniques suitable for adult patients describes the principles, application, strengths and weaknesses of modalities including active cycle breathing techniques (ACBT), intrapulmonary percussive ventilation (IPV), the Flutter® valve and high-frequency compression (HFCC)/high frequency chest wall oscillation (HFCWO).
  15. Rueling S, Adams C. Close to the vest: a novel way to keep airways clear. Nursing. 2003; 33:56-57.
    This brief nursing journal article describes favorable clinical experience, patient tolerance and acceptance and staff time and labor savings using high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) in the in-patient setting.
  16. Schramm CM. Current concepts of respiratory complications of neuromuscular disease in children. Curr Opin Pediatr 2000; 12: 203-207.
    Chronic neuromuscular diseases affecting the respiratory muscles may promote development of restrictive pulmonary disease, ineffective cough, atelectasis, pneumonia and chronic respiratory insufficiency leading to respiratory failure. This review discusses the necessity for therapeutic strategies to augment cough and airway clearance, improve lung volumes, and support the neuromuscular disease patient with progressive ventilatory failure; such techniques are associated with improved longevity and quality of life in this patient population. The growing use of high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) for neuromuscular patients is acknowledged: “Various chest physiotherapy techniques have been added [to the pulmonary care] regimen to help thin the viscoelastic properties of airway mucus and enhance its clearance. Traditionally, these have entailed chest percussion and postural drainage, but…external vibration from a pneumatic vest [is] beginning to be employed for these conditions.”
  17. Swigeris JJ, Stoller JK. A review of bronchiectasis. Clin Pulm Med 2000; 7 (5): 223-230.
    Patients with bronchiectasis produce large volumes of sputum and experience chest pain and shortness of breath associated with airflow limitation and recurrent respiratory infections. Disease progression is marked by increasingly frequent, severe episodes of exacerbation. In this review of bronchiectasis, clinical symptoms, eitiology, pathophysiology diagnosis and current management practices, airway clearance therapy (ACT) is discussed in terms of exacerbation control and symptom relief. Recommendations include,”…devices used to increase sputum volume and clearance include external high-frequency chest wall vibrators, one example of which is the Vest [high frequency chest wall oscillation (HFCWO).”
  18. Toder DS. Respiratory problems in the adolescent with developmental delay. Adolescent Medicine: State of the Art Reviews 2000; 11:617-631.
    Review This overview of respiratory complications prevalent in adolescents with severe cerebral palsy or other neuromotor/neuromuscular disorders, together with developmental delay, emphasizes the importance of routine preventative and therapeutic secretion clearance. Risk factors for pulmonary problems include drooling, aspiration, gastroesophageal reflux, and musculoskeletal deformity. Airway clearance treatment options suitable for this population are evaluated; the author singles out “the external chest percussion vest” [high frequency chest compression (HFCC)/high frequency chest  wall oscillation (HFCWO)] for management of atelectasis in patients with and without tracheostomies.
  19. van der Schans CP, Postma DS, Koeter GH,Rubin BK. Physiotherapy and bronchial mucus transport. Eur Respir J 1999; 13(6): 1477-1486.
    This review discusses use of laboratory and clinical data to evaluate the efficacy of various airway clearance techniques in different patient populations. Outcome variables, such as bronchial mucus transport measurement, measurement of the amount of expectorated mucus, pulmonary function, medication use, frequency of exacerbation and quality of life, are recommended. Measurement of the transport rate of mucus in the airways using a radioactive tracer is advocated for short-term studies. The usefulness of pulmonary function tests in short-term studies is challenged.
  20. van der Schans CP. Airway Clearance: assessment of techniques. Paediatr Respir Rev. 2002; 3 (2): 110-114.
    Mucus hypersecretion and retention of mucus are common in patients with pulmonary disease. In order to reduce mucus retention, airway clearance techniques are used. The value of the most commonly used outcome parameter in clinical situations – pulmonary function testing – is called into question. For research purposes, measurement of the transport rate of mucus in the airway using a radioactive tracer technique is identified as the most direct outcome parameter. Disease course and progression are considered meaningful long-term outcome parameters.
  21. Wagener JS, Headley AA. Cystic fibrosis: current trends in respiratory care. Resp Care 2003; 48 (3): 234-245.
    Prolonged bronchial obstruction, infection and inflammation result in the end stage lung disease, or bronchiectstasis, that proves fatal to the majority of cystic fibrosis (CF) patients. This review discusses the importance of early diagnosis, effective treatment and responsive outcomes monitoring. In the absence of a cure, effective respiratory therapies, including airway clearance interventions such as high frequency chest compression (HFCC), are the primary means to extend life and improve its quality. Authors comment, “High-frequency chest compression is clinically safe and effective in CF patients. Unlike CPT (chest physiotherapy…the patient can independently perform HFCC. Patient acceptance, and therefore adherence with prescribed routine, may also be better with HFCC…although the initial equipment cost is high, subsequent savings in therapist time can be expected.”
  22. Warwick, WJ. Center Directors Remember: Minnesota. In: Cystic Fibrosis in the 20th Century, CF Doershuk, Ed., (AM Publishing, Cleveland, OH. 2001)
    Cystic Fibrosis in the 20th Century: People, Events, and Progress, tells the story of more than 60 years of advances in understanding and managing the disease. In one of several chapters written by directors of major U.S. cystic fibrosis treatment centers, Dr. Warren J Warwick, inventor of the first high frequency chest compression (HFCC) machine for clinical use, summarizes his experience with the therapy: “The vest technology has proven to be the most effective way to remove mucus from the lungs of patients with CF and many other lung diseases.”

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