ReviewAirway Clearance Techniques for Primary Ciliary Dyskinesia; is the Cystic Fibrosis literature portable?
Section snippets
Primary Ciliary Dyskinesia (PCD)
PCD is a rare, predominantly autosomal recessive condition in which ultra-structure abnormalities of ciliated cells cause impaired cilial function [1]. Impaired cilial function results in changes across the body including situs abnormalities (dextrocardia, situs inversus totalis), chronic otitis media, sinusitis, rhinitis, subfertility, and the main focus of this review; impaired mucociliary clearance from the lungs [2]. Normal ciliary function is essential to clear the respiratory tract from
Epidemiology
The prevalence of PCD in children aged 5–14 years is estimated to be between 0.33–0.5 per 10,000 across Europe [7]; lower than the European prevalence of CF (0.74 per 10,000) [8]. Variance in PCD prevalence rates may be true variance across different populations, illustrated by the unusually high prevalence of 4.4 per 10,000 amongst the Bradford Pakistani population [9]. However, spurious variance may be due to under-diagnosis, with patients mis-diagnosed as idiopathic bronchiectasis or asthma
PCD management
Links between early diagnosis, lower incidence of bronchiectasis and stable lung function have been established for over two decades [11] and later diagnosis has been associated with increased frequency of Pseudomonas aeruginosa colonisation and lower baseline lung function (FEV1) [10]. Once diagnosed, condition specific management can be commenced. A survey of paediatric PCD patients in European centres (including Turkey, Israel, Serbia and Estonia), conducted between 2007 and 2009, aimed to
Airway Clearance Techniques (ACTs)
ACTs are a range of interventions which aim to facilitate clearance of mucus from the airways. These are typically advised by a physiotherapist across a range of conditions in which the normal physiological mucociliary escalator is unable to effectively clear the airways of the mucus produced. Physiologically ACTs aim to influence regions of ventilation, splint open small airways, access channels of collateral ventilation, optimise and bias airflow, manipulate the location of the equal pressure
Physiotherapy evidence in PCD
Systematic review of the paediatric PCD literature in databases Medline, Embase, Cinahl and Amed found 375 studies using search terms which included variant terms of PCD and physiotherapy or ACTs. Of these 342 were excluded (62 duplications, 28 adult studies, 1 animal study and 252 which did not actually involve ACTs in PCD. Of the remaining 35 results, 18 comprised of guidelines, literature reviews, conference summaries or PCD overviews which were searched for relevant contents and references.
Evidence for ACTs in PCD
A randomised cross-over design was used to compare HFCWO with postural drainage percussion and vibrations (PDPV) in 12 positions performed by a physiotherapist [17]. Twenty four paediatric PCD patients received one intervention for 5 days and after a 2-day washout period; they received the alternate intervention for 5 days, with patients randomly allocated to receive either manual techniques or HFCWO first. Outcomes included lung function and patient’s reports of both comfort and perceived
Evidence for exercise in PCD
PCD consensus statements suggest regular exercise may assist secretion clearance and have a positive bronchodilation in PCD [2], [5]. Again, there is a paucity of literature with only 2 studies pertaining to exercise in paediatric patients with PCD identified in the search. One study evaluated the effects of exercise and a 200 μg dose of salbutamol on lung function in 12 paediatric PCD patients [14]. The interventions of 8 minutes on a treadmill and a dose of salbutamol were given in succession
Key differences between CF and PCD
With minimal evidence of the effectiveness of ACTs in PCD, practice is often based on evidence extrapolated from research in CF [18]. Yet, there are notable differences in the pathophysiology, disease trajectory and symptoms of the two conditions [19] and it is important to consider differences between the conditions which may influence clinical application. PCD is often likened to CF, which is also an inherited condition in which mucociliary clearance is impaired. However in PCD the impairment
Selection of appropriate ACTs
There are a number of interventions shown to be effective in CF which are widely applicable to PCD due to common physiological principles. Normal mucus clearance occurs through a combination of ciliary clearance and airflow forces shearing and mobilising mucus. This led to the development of Autogenic Drainage (AD) [25], which guides patients through the manipulation of lung volumes and airflows to move mucus from smaller to larger airways. With the absence of an effective ciliary beat, one of
Optimisation of ACTs
The position in which patients undertake an ACT can be varied and positioning is commonly used alongside other ACTs to target areas of lung and optimise regional ventilation [30]. Ventilation is usually greatest in the dependant regions of the lung; the lower lobes in sitting, the lowermost lung areas in supine and the dependant lung in side lying [31]. However caution should be taken when applying positioning principles as ventilation is thought to be to be highly variable even amongst healthy
Consideration of mucus properties
In CF, impaired Cl− and HCO3− secretion and increased epithelial Na+ absorption result in dehydrated mucus, which when compounded by the effects of inflammatory mediators make CF mucus understandably challenging to clear. Despite differing pathophysiology, mucus from PCD patients has been found to have similar biophysical and transport properties to CF mucus [18], with significantly higher interleukin-8 levels in PCD mucus than in CF mucus [18], [20]. Within CF, mucolytic dornase alpha
The impact of undertaking ACTs
Undertaking daily treatments such as ACTs are time-consuming and can be a considerable treatment burden for patients causing psychosocial implications. Within PCD, ACTs can serve as a cue that individuals might feel different to their peers and reminders of disease [40]. Coughing is one of the most visible signs of abnormality in PCD, yet one of the essential elements of an effective ACTs session. Coughing can be a stigma for patients with PCD and some children and young people cough supress to
Future research directions
Greater understanding of the physiological differences between PCD and CF will add to understanding of how mucociliary clearance is facilitated and when it is impaired. Whilst it would be unethical to withhold ACTs from patients with PCD, randomised-controlled trials of their effects, knowledge of the benefits of undertaking daily time-consuming treatments is needed. Large PCD specific trials of pharmacological agents such as mucolytics are also required to quantify the ‘true’ risks and
Conclusion
In the absence of PCD-specific research, clinical practice must be based on the best available evidence and expert opinion. Knowledge and understanding transposed from studies in people with CF have provided the foundation on which PCD care has been built. However, there are fundamental physiological differences between the conditions and caution needs to exercised prior to more comprehensive extrapolation. The lack of research in PCD populations is well recognised but it is hoped that the
Educational aims
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To review the existing evidence for chest physiotherapy in paediatric PCD
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To discuss the differences between PCD and CF pertaining to mucus clearance
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To explore the appropriateness of extrapolating CF research to PCD chest physiotherapy practice
Funding
This work was supported by the Leeds Teaching Hospitals Charitable Foundation [grant numbers 9R01/15-04].
Acknowledgements
Thank you to Rosemary Ball, Clinical Specialist Physiotherapist and Christine Blackburn, Highly Specialist Physiotherapist for their proof reading, and the Leeds Paediatric Physiotherapy team and The North of England Paediatric PCD Management Team for their support.
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