Physiological Principles of Airway Clearance Techniques Used in the Physiotherapy Management of Cystic Fibrosis

ARTICLE IN PRESS

Current Paediatrics (2005) 15, 233–238

www.elsevier.com/locate/cupe

Physiological principles of airway clearance techniques used in the physiotherapy management of cystic ﬁbrosis

Diane RogersÃ, I.J.M. Doull

Paediatric CF/Respiratory Unit, Children’s Centre, University Hospital of Wales (UHW), Health Park, Cardiff CF14 4XW, UK

KEYWORDS Summary Cystic fibrosis (CF) has a reported incidence of one in 2500 live births in Cystic fibrosis; the UK and is the most common cause of suppurative lung disease in Caucasian Physiotherapy man- children. Effective management of the respiratory component of this condition agement; relies on optimal antibiotic therapy combined with efficient clearance of retained Retained secretions; airway secretions. Physiotherapy management of CF aims to address patient Airway clearance problems associated with the impairment of mucocilliary clearance mechanisms. techniques (acts) Over the last two decades a number of airway clearance techniques (ACTs) used during physiotherapy treatment have been developed and studied within the CF paediatric population. Many of these ACTs share common physiological principles that are well described and reported. This article gives a brief overview of the most commonly used techniques used in the paediatric CF population. & 2005 Elsevier Ltd. All rights reserved.

assessment, be provided with individual Practice points physiotherapy management plans Airway clearance techniques (ACTs): Physiotherapy assessment: All paediatric Physiotherapy ACT enhances the clearance patients diagnosed with CF should be of excess bronchial secretions in the assessed by a physiotherapist experienced paediatric patient with CF resulting in in the management of this condition decreased airway obstruction, de- Individual patient management plans: All creased airway resistance and improved paediatric CF patients should, following ventilation Treatment evaluation and outcome mea- sures: Appropriate measurement tools ÃCorresponding author. Tel.: +44 2920745250; should be used to evaluate physiotherapy fax: +44 2920743587. treatment interventions E-mail address: [email protected] (D. Rogers).

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Education/advice on exercise activity and ex- Research directions ercise programmes. Advice on posture and treatment for musculos- Infant treatment: The development of keletal pain. neonatal screening programmes has resulted Oxygen therapy and non-invasive ventilation. in reduced age at diagnosis of CF. Further Advice and treatment of stress incontinence research is required to determine the effect symptoms. this will have on early physiotherapy treatment interventions Combining treatment modalities:Thebur- Airway mucus in CF den of daily routines of airway clearance techniques (ACTs) and inhalation therapy is The presence of excessive airway secretions in CF significant. Further research could determine due to chronic infection and mucosal inflammation how combining these treatment modalities and the retention of infected secretions due to may benefit the paediatric patient with CF bronchoconstriction and impaired mucocliiary Novel ACTs: Whilst it is important that clearance leads to the pattern of airway obstruc- paediatric CF patients are offered the most tion, mucus plugging, atelectasis, airway instability up to date, effective and socially acceptable and hyperinflation seen.5 ACTs available, the introduction of a novel Removal of retained secretions using physiother- ACT should be properly evaluated. apy ACTs will result in decreased airway obstruction and resistance, improved ventilation and air flow, decreased shunting and reduced ventilation/perfu- sion mismatch.6 There may also be some benefit in the removal of the bacterial products produced Introduction during chronic infection, which have been shown to further disrupt local defence mechanisms.7 The clinical manifestation of cystic fibrosis (CF) is characterised by chronic pulmonary infection and pancreatic insufficiency, with associated problems such as cystic fibrosis related diabetes (CFRD) and Airway clearance techniques liver disease generally developing as later compli- cations. The main cause of morbidity and mortality In combination with an effective cough, physiother- remains pulmonary disease and much of the clinical apy ACTs used in the treatment of paediatric CF can management is aimed at the treatment of a consist of a number of different modalities8 patient’s respiratory problems.1 including: Along with antibiotic therapy, physiotherapy management is an important component in the Use of gravity to aid mucus transport—postural treatment of the respiratory problems seen and has drainage (PD). been shown to be of benefit in the removal of External application of forces against the chest excess airway secretions2 and in the treatment of wall—percussion, vibrations, shaking, high-fre- sensations of breathlessness (SOB) and decreased quency chest wall compression (HFCC). exercise activity and tolerance.3 Breathing techniques—active cycle of breathing Physiotherapy treatment should be introduced at techniques (ACBT) and autogenic drainage (AD). diagnosis by a clinician experienced in the manage- Devices designed to introduce positive pressure ment of this condition.4 In collaboration with the and/or oscillation into the airways—positive child and their family the physiotherapist should expiratory pressure (PEP) masks, flutter, cornet develop individual management plans based on and accapela, intrapulmonary percussive venti- patient assessment. Depending on the patient lation (IPV). problems identified, a number of physiotherapy Physical activity and prescribed systemic exer- treatment modalities may be introduced. cise programmes. These include: It is important to note that whilst ACTs used Airway clearance techniques (ACTs), to aid in the within the paediatric and adult CF populations removal of retained secretions. share common principles, there are important Adjuncts to ACTs such as aerosol therapy (in- physiological differences between the two groups halers and nebulisers). and rationales for use may differ substantially. ARTICLE IN PRESS

The principles of physiotherapy in CF 235

These differences are most apparent in the ques should be more effective over solid, i.e. neonate, but are present throughout infancy and consolidated or atelectatic, lung segments than disappear only as growth and development evolves healthy lungs where aerated lung tissue would through childhood into adulthood.9 absorb any pressure changes. In clinical practice such techniques are usually applied directly over areas of lobar or segmental lung disease. In wide- Gravity assisted positions (postural drainage) spread disease pathologies such as CF, they are used with the understanding that forces generated One of the earliest and frequently used ACTs in CF, during therapy may be attenuated, thus reducing postural drainage, requires the patient to be placed efficacy. in positions that anatomically favour the gravity Care must also be taken when using manual directed movement of secretions towards the techniques with newborn and very immature upper airways, from where secretions can be infants to ensure that excessive movement of the cleared by coughing. The rationale for this techni- unsupported head does not occur. Whilst some que assumes that additional gravitational forces on concerns have been reported in neonatal manage- vertically positioned bronchi will enhance impaired ment13 there have been no reports of adverse mucocilliary transport. However in CF, considera- effects in CF patients. tion must be given to the fact that airway secretions are hyper viscid and effective drainage times can result in prolonged treatment sessions Breathing techniques that may be non-acceptable to children and families. Recent studies have also shown that the Active cycle of breathing techniques (ACBT) prevalence of gastro-oesophageal reflux (GOR) in The ACBT is the most commonly used ACT in the infants and young children with CF may vary from UK.14 ACBT is a cycle of breathing techniques 10 between 35% to 81% and that standard PD comprising: positions may not be recommended in these patients.11 Breathing control (BC)—relaxed tidal volume breathing using minimal effort by the patient. Manual techniques (percussion, vibrations This aims to decrease airway obstruction and and shaking) improve airflow by reducing bronchoconstriction and by using collateral ventilation to open up Manual techniques such as percussion, vibrations airways and get air behind secretions.5 and shaking are generally performed whilst the Thoracic expansion exercises (TEE)—where the patient is placed in postural drainage positions to patient is encouraged to inspire to full lung further enhance mucocilliary clearance. Percussion volume. This technique also utilises collateral consists of a rhythmical clapping on the patient’s ventilation and the interdependence mechan- chest wall with a cupped hand, whilst the patient is ism15 to move air into smaller airways obstructed asked to take deep breaths. Vibrations consist of a by secretions. During inspiration, expanding fine oscillation of the therapist’s hands placed alveoli exert a force on adjacent alveoli that either side of the patient’s chest wall and directed may assist in the re-expansion of collapsed inwards, while shaking is a similar but coarser ventilatory units; these effects are felt to be movement in which the hands rhythmically com- more marked during deep breathing. press the patient’s chest wall again in an inwards The forced expiration technique (FET) or ‘huffing direction. The latter two techniques are performed technique’—where the patient performs a com- during exhalation following a maximum inspira- bination of one or two forced expirations tion.12 combined with periods of breathing control.5 The exact physiological mechanism by which The rationale behind the FET is based on the manual techniques aid the removal of secretions physiological concept of the equal pressure point is not proven. The hypothesis is that the application (EPP), which is described ‘as the point at which of an external force to the chest wall creates pressure within the bronchi (Pbr) equals peri- intrapleural pressure changes that are transmitted bronchial (Ppl) pressure during a forced expira- through the thoracic cage and lung tissue, loosen- tion’.15 During expiration the EPP starts at the ing any secretions attached to the airway wall. mouth and moves peripherally towards the lobar These secretions then collect in the lumen of the and segmental bronchi but does not extend to airway from where other mucociliary mechanisms the terminal units. Downstream of the EPP, can aid in removal. If correct, then these techni- dynamic compression and collapse of the airways ARTICLE IN PRESS

236 D. Rogers, I.J.M. Doull

occurs because Pbr becomes less than Ppl, physiotherapy treatment should recognise that expiratory flow is compromised, airflow becomes they are poorly developed during infancy but may increased and more turbulent thus mobilising be present from 2 to 3 years of age. secretions.5 In healthy adults, resistance to airflow through collateral channels is high in relation to airflow In clinical practice the FET can be started at resistance within the conducting airways and different lung volumes thereby clearing different therefore does not readily occur. However in sized airways. As clearance of secretions using the disease, when airflow resistance is increased within FET is dependant on patient lung volume, ‘huffing’ the conducting airways by the presence of retained to low lung volume will move more peripherally secretions or airway collapse, resistance within situated secretions and a ‘huff’ at high lung volume collateral channels is reduced in relative terms and will clear secretions from more proximal airways. airflow through collateral channels is more likely to However, using the EPP to mobilise secretions can occur. result in an increase in airway obstruction, parti- In clinical practice, PEP therapy allows more air cularly in diseased or immature airways which may to enter the airways through collateral channels be anatomically unstable and/or hyper reactive.9 during inspiration, than escapes during expiration. This results in the development of a pressure Autogenic drainage (AD) gradient that builds up behind sputum plugs, moving secretions into more central airways from AD is a three phase breathing technique developed 18 in Belgium.16 It aims to increase airflow through where it can be more easily removed. Positive airways whilst avoiding the early airway closure pressure within the airways is also thought to that occurs in diseased or damaged airways as prevent compression-induced collapse, splinting previously described. AD aims to control expiratory open the airways during expiration and thus further assisting with the clearance of secretions from flow at differing lung volumes whilst avoiding the 19 generation of an EPP during expiration, allowing distal airways. flow rates to last longer, therefore move secretions A commonly used PEP therapy system consists further during each expiration.16 During therapy, of a close fitting mask and a one-way valve to tidal volume breathing is maintained at low lung which expiratory resistors can be attached. A volume (un-stick phase), mid lung volume (collect manometer placed in parallel with the resistor phase) and high lung volume (evacuate phase) can be used to determine the correct pressure used depending on whether the secretions are located during therapy. In low-pressure PEP therapy the within the peripheral, proximal or central airways, diameter of the resistor used for treatment is respectively. AD has shown to be of particular determined, using tidal volume breathing, to give a benefit to patients with significant airway hyper- steady PEP of 10–20 cm H2O during the middle part reactivity17 but in clinical practice patients with of expiration. High-pressure PEP therapy uses the advanced disease might find sustained breathing at same equipment but sustained expiratory pressures low lung volumes uncomfortable. achieved usually range between 40 and 100 cm of H2O. The physiological effects of high pressure Positive expiratory pressure (PEP) PEP in CF can be explained by increased collateral airflow to underventilated lung regions, effective A number of PEP devices have been developed for splinting of the damaged airways during a forced use with paediatric CF patients. These include low- expiration manoeuvre and by allowing the patient 18 pressure PEP therapy, high-pressure PEP ther- to expire to a volume greater than his/her usual 19 20 apy and oscillating PEP therapy. PEP therapy is forced vital capacity (FVC).5 This technique can be based on the physiological principles of collateral useful for the paediatric patient with more un- 15 ventilation, which suggests that ventilation and stable airway disease but as it requires significant airflow can occur between adjacent lung segments patient effort may not be suitable for those who through anatomical channels such as: tire easily. Devices are now available that offer a combina- Interbronchiolar channels of Martin tion of variable positive airways pressure and Bronchiole—alveolar canals of Lambert oscillation of air within the airways during expira- Alveolar pores of Kohn tion. These include the Flutters, RC-Cornets and Acapellas. Exhalation through these devices gen- In children, any reliance on collateral ventilation erates both oscillations of positive pressure in the channels to enhance mucociliary clearance during airways and repeated accelerations of expiratory ARTICLE IN PRESS

The principles of physiotherapy in CF 237 airflow that have been shown to result in improved As novel ACTs are introduced to our paediatric CF sputum clearance.20 Physiologically this effect can populations it is important to ensure that their be explained by: physiological basis is established and their efficacy examined by prospective research. Oscillating positive pressure causing the diameter of the airways to increase and thus prevent early airway collapse. References Pressure induced vibrations within the airway walls displacing secretions into the airway lu- 1. Goodchild MC, Dodge JA. Cystic fibrosis: manual of diagnosis men. and management. London: Bailliere Tindall; 1989. Repeated accelerations of expiratory airflow 2. Desmond KJ, Schwenk WF, Thomas E, Beaudry PH, Coates favouring movement of secretions from the distal AL. Immediate and long-term effects of chest physiotherapy in patients with cystic fibrosis. 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