High frequency chest wall oscillation in cystic fibrosis.

Airway clearance is considered an integral component of the management of cystic fibrosis (CF).RecentCFpulmonaryguidelines made recommendations using the US Prentative Service task Force (USPSTF) grading scheme (a system which provides a mechanism toweigh the quality of evidence and the potential harms and benefits) on airway clearance. 2 These guidelines recommended thatairwayclearanceshouldbeprovidedtoall patients with CF (grade B recommendation: highcertainty that thenet benefit ismoderate and at least moderate certainty that the net benefit ismoderate to substantial). They also summarise the evidence for the efficacyof one airway clearance regime versus another and recommend (grade B) that no airway clearance regime has been shown to be superior to others although they recognise that, for any individual, one airway clearance regime may be superior. They advocate that patients shouldbeable tochoose, incollaborationwith the therapist,which airway clearance regime/ regimes they wish to use. Other guidelines and systematic reviews as well as many primary trials agree that there is no clear advantage of one particular airway clearance regime over another. The active cycle of breathing techniques (ACBT) is the standard airway clearance regime in the UK, although in the last few years other forms of airway clearance (eg, autogenic drainage) as well as a range of adjuncts have become popular (eg, positive expiratory pressure (PEP) mask, flutter and Acapella). These adjuncts are often provided “free” at the point of delivery to the patient within the current healthcare system. In the USA, high frequency chest wall oscillation (HFCWO; known as the Vest) is widely used and is purchased for patients under various insurance schemes. HFCWO is notwidely provided to patients with CF in the UK or the Republic of Ireland, and patients who currently use it have often purchased it themselves. The UK and the Republic of Ireland have experienced a huge move by patients to have access to HFCWO. At present, patient choice to use HFCWO is set against its significant cost (around £8000 per Vest), and there is a lack of sound evidence on its superiority or on equivalence to othermuch less expensive treatments that are currently part of standard treatment for CF. The CF pulmonary guidelines have summarised the evidence available for HFCWO compared with other forms of airway clearance. Studies (n1⁄410) comparing HFCWO with other forms of airway clearance were mostly limited to very short studies comparing one session or a number of days of treatment. Some of the studies have compared HFCWO with conventional chest physiotherapy (postural drainage and percussion). In general, these studies showed no difference in lung function or sputum production or favoured HFCWO. Conventional chest physical therapy (CCPT) can be associated with some side effects.WhenCCPT is performed in a head-down position, it can aggravate gastro-oesophageal reflux and induce adverse reactions, including bronchospasm, changes in cardiac rhythm and increased intracranial pressure. Moreover, patients find CCPT so burdensome that adherence with the prescribed treatment regime is probably less than 50%. Even hospitalised adolescents in a controlled setting showed significant (35%) nonadherence to a CCPT regime. Postural drainage and percussion is not considered standard airway clearance in the UK, and therefore the resultsdwhether positive or notdhave limited applicability in the UK. Some studies (also short-term) have compared HFCWO with treatments recognised as standard airway clearance in the UK. ComparedwithPEP, therewasnodifference in either lung function or sputum production. When compared with oscillating PEP, one study showed a benefit in terms of sputum production and found no difference in lung function. 16 When HFCWOwas compared with ACBT, ACBT was better in terms of sputum production and lung function. The lack of published evidence comparing HFCWOwith airway clearance techniques frequently used in the UK and Europe provided the main justification for the randomised crossover study by Osman and colleagues in this issue of Thorax (see page 196). The study compares the efficacyof 2 daysofHFCWOwith2 daysof usual airway clearance in 29 patients with CF. The crossover design used in this study (chosen presumably to improve the efficiency of the study and also to facilitate patient comparison between treatments) assumes that the treatment on one day did not “carry over” and alter the response to the treatment on the next day, and an analysis is presented which suggests that this was the case. The authors optimised their design by ensuring that patients were familiarised with both interventions, HFCWO was optimally delivered using recommended instructions for use, and the length of each treatment session was standardised. The primary outcome measures were carried out by an independent assessor and included wet weight of sputum (collected during the treatment session and also during each 24 h session), forced expiratory volume in 1 s, pulsed arterial oxygen saturation, urinary leakage and patient-reported preference. The study showed that patients cleared more sputum (during a treatment session and over 24 h) using usual airway clearance than with HFCWO. Patients perceived usual treatments to bemore effective, and thiswasnot affected by order or day of treatment. The authors conclude that, considering the cost of HFCWO compared with other airway clearance techniques and the differing healthcare systems in the USA and the UK, it is unlikely that HFCWO will be the first choice of airway clearance in the UK. It is indeed unlikely thatHFCWOcould be offeredwithin current funding arrangements in the UK National Health Service unless future research or the results of currently active trials such as the 1-year Canadian trial comparing HFCWO with their standard treatmentdPEP (http://ClinicalTrials.gov identifier NCT00817180) show significant benefits of HFCWO that outweigh the considerable cost. Further research with HFCWO remains important, as we have an obligation to provide our patients with scientific evidence to justify our current practice. Osman and colleagues have provided preliminary data which could be used to design a long-term study comparing the efficacy of HFCWO with usual airway clearance in the UK. Such a study would be complex, multicentre and expensive, and yet unlikely to attract the same funding as other types of trials such as new drug therapies. Airway clearance is rated as one of the most troublesome parts of treatment in CF and sodperhaps in response to patient demandsdpatient organisations should seek to lobby funding bodies to prioritise and/or commission research on HFCWO. Collaboration between teams of researchers and clinicians will be essential to design and Correspondence to Dr J M Bradley, Physiotherapy, Health and Rehabilitation Sciences Research Institute, University of Ulster, UK; [email protected]