Eur J Pediatr (2008) 167:607–612 DOI 10.1007/s00431-008-0689-y

REVIEW

Airway clearance techniques to treat acute respiratory disorders in previously healthy children: where is the evidence? Kris De Boeck & François Vermeulen & Myriam Vreys & Marleen Moens & Marijke Proesmans

Received: 29 January 2008 / Accepted: 6 February 2008 / Published online: 6 March 2008 # Springer-Verlag 2008

Abstract Airway clearance techniques are an important part of the respiratory management in children with cystic fibrosis, 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. The current review explores the evidence behind this use of airway clearance techniques in children without underlying disease. 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. Keywords Chest physiotherapy . Airway clearance techniques . Respiratory disorders . Child . Asthma . Bronchiolitis

Introduction Acute respiratory disorders in childhood are a major health issue. They account for half of the outpatient contacts for K. De Boeck (*) : F. Vermeulen : M. Vreys : M. Moens : M. Proesmans Department of Paediatrics, University Hospital of Leuven, Herestraat 49, 3000 Leuven, Belgium e-mail: [email protected]

acute illness in preschool children and a third of the consultations in school-age children [8]. Also, for acute paediatric admissions to hospital, respiratory disease is the most common diagnostic category [25]. Most of these respiratory diseases have a viral aetiology and treatment is mainly supportive. Even when managed in the community, these diseases are associated with a substantial cost and are a major cause of loss of productivity for the parents [22]. Several strategies are used in an effort to decrease the disease burden and speed up the recovery. Amongst these, cough medicines and chest physiotherapy are often prescribed. We want to review the evidence about the use of chest physiotherapy in acute respiratory disorders in previously healthy children. The normal respiratory tract has an elaborate defence mechanism to protect itself against damaging agents, such as bacteria and inhaled particles. The mucociliary transport system and effective cough play a crucial role in this defence; many other factors, such as neutralising antibodies and phagocytosis by alveolar macrophages, complete it [31, 32]. During lower respiratory tract infections, the mucociliary ladder can become overloaded by excessive mucus production or be impaired by an inflammatory process with loss of ciliary function. Coughing, by itself, is a protective mechanism, but coughing can become ineffective and tiring to the patient when the cough effort is out of proportion with the secretions that are cleared by it. The latter scenario is well known in patients with pertussis. The aim of chest physiotherapy during acute infection is to speed up airway clearance, thereby, improving breathing mechanics and gas exchange, and, ultimately, hastening the patient’s recovery. Several techniques are in use and there is some discussion on what is the most appropriate terminology. A group of expert physiotherapists lead a movement towards leaving the term “chest physiotherapy” behind and to replace it by

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“airway clearance techniques” as a group name for all of the techniques and devices that have been developed [20]. That term is appropriate because the treatment aim is, indeed, to clear secretions from the airway, thereby, promoting airway patency and efficient gas exchange. “Chest physiotherapy” can be confused with “conventional chest physiotherapy,” denominating the older techniques that primarily concern chest wall clapping, percussion and postural drainage. Since so many techniques are available, the most appropriate action will be to mention the specific technique or techniques used, e.g. manual chest compression during expiration, autogenic drainage, active cycle of breathing, manual cough assist techniques, devices directed at huff coughing, high-frequency chest wall compression, intrapulmonary percussive ventilation, oscillatory devices such as flutter, and positive expiratory pressure (PEP) mask and their derivatives. Unfortunately, being specific with words when it concerns treatment with “chest physiotherapy” or airway clearance techniques has not yet become general practice, nor is there a standard consensus paper to refer to yet. For a short description of these individual techniques, see http://www.cfww.org/IPG-CF [20] . Often, a combination of therapies is applied, adapted not only to the patient’s age, degree of cooperation and disease state, but also according to the specific skills and preferences of the physiotherapist. For this review, we will further use the general term “airway clearance techniques” and mention the specific technique applied in a particular study or state “chest physiotherapy” if the study did not specify what technique was used. The variability in the available techniques and the difference in expertise by the physiotherapist hamper the objective evaluation of airway clearance techniques as additive treatment in acute respiratory disorders. Also, it is not clear which outcome variable is optimal for use in clinical trials. Older studies merely focussed on acute improvement. i.e. less coughing, improvement in a “custom-made” respiratory score and acute change in lung function. In this time of evidence-based medicine, more meaningful endpoints, such as earlier discharge from hospital or avoiding long-term sequels in respiratory function, are more appropriate. Further impairing research is the fact that control groups are difficult to define and sham treatments are inappropriate or impossible. Keeping these limitations in mind, we will review the current evidence for the use of airway clearance techniques in previously healthy children with an acute respiratory illness.

Bronchiolitis Bronchiolitis is a common viral lower respiratory tract infection in young children. Several viruses are known to

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cause bronchiolitis, but RSV and metapneumovirus are the most frequent [13]. In severe bronchiolitis, there is lower airway obstruction secondary to necrosis of the respiratory epithelium and loss of ciliated epithelial cells. Exsudate, cell debris and peribronchial lymphoid infiltration cause plugging of the airway lumen. Clinical signs of infection include cough, tachypnoea, retractions, wheezing and crackles. In established disease, treatment is mainly supportive, with monitoring, oxygen and fluid therapy as key components [1]. Based on the results of three randomised clinical trials, chest vibration and percussion do not reduce the length of hospital stay, oxygen requirements nor improve the severity clinical score [29]. The sample size in these studies varied from 32 to 90 infants. In a non-controlled study in ventilated infants with bronchiolitis, a French group reported slightly improved oxygenation and increased tidal volume immediately following manual compression during expiration and endotracheal suctioning [5]. Despite this lack of evidence, “chest physiotherapy” aimed at improving airway obstruction and decreasing the work of breathing continues to be prescribed widely in young children with viral lower respiratory tract disease [4]. Interventions used and outcomes obtained were also described in 601 patients with viral lower respiratory infection consecutively admitted to ten children’s medical centres [36]; 519 of these children suffered from bronchiolitis. The use of “chest physiotherapy” as additive treatment varied from 4 to 71% of the cohort. This variability was not influenced by disease severity or population characteristics, but reflected local practice preference. It also did not influence patient recovery. Todd et al. [34] likewise demonstrated large differences in practices and resources used between hospitals. None of these studies reported which airway clearance techniques were being used. The authors did, however, prove that therapeutic behaviours can be changed. The introduction of evidence-based clinical care guidelines in one of the hospitals was associated with a significant change in practice. In the index hospital, the use of “chest physiotherapy” decreased by 30%.

Pneumonia Pneumonia is an inflammation of the lung parenchyma and is mostly caused by micro-organisms. Viral pneumonia is more common during the winter months. The same viruses that cause bronchiolitis can cause pneumonia and, also, the clinical pictures overlap. The chest radiograph is characterised by diffuse or localised infiltrates. On clinical grounds, it is difficult to differentiate pneumonia from viral, mycoplasma and bacterial origin, unless there is a typical lobar pneumococcal pneumonia with sudden onset

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of fever and high white blood cell count. Antibiotic therapy is mandatory in bacterial pneumonia [16]. There is no recent study assessing the role of airway clearance techniques as adjunctive treatment for pneumonia. Only intermittent positive pressure breathing, postural drainage, vibration and percussion have ever been evaluated. The existing literature dates from the late 1970s and mid-1980s [6, 15, 23, 33]. By modern standards, these studies have poorly defined the patient inclusion criteria and only two studies are restricted to children [23, 33]. A positive effect was never demonstrated and a significantly longer duration of fever in the group treated with vibration, percussion, postural drainage and external help with breathing was reported in one study [6]. An additional reason for not inflicting airway clearance techniques on otherwise healthy children with acute pneumonia is that the disease process happens in the very peripheral airspaces; the central airways are usually clear of secretions during bronchoscopic inspection. Only during the resolution phase do moderate amounts of secretions at times appear in the airways.

Acute severe asthma Acute asthma continues to be a common reason for seeking emergency medical advice and, in some case series, 30– 40% of these children end up being admitted to hospital [7]. One well-designed study randomised 38 children aged 6 to 13 years to chest physiotherapy or placebo visit within 24 h of hospital admission. Over the next 2 days, chest physiotherapy using techniques to help clear secretions, achieve relaxation, minimise ineffective breathing movements and optimise drug therapy did not improve lung function over the effect seen with asthma drug therapy [3]. A Cochrane analysis discusses trials about various forms of manual therapy to relieve asthma symptoms with the exclusion of isolated postural drainage, i.e. massage, mobilisation of the chest, clapping, vibration and shaking. These therapies are given by diverse therapists, including chiropractors, osteopaths and respiratory physiotherapists. The review found no evidence that any of these therapies are helpful [18].

Atelectasis Atelectasis, the partial or total collapse of a lung segment or lobe, is not so common in a previously healthy child. It is a condition rather than a disease entity, since the possible causes are multiple. Foreign body aspiration, external airway compression, exacerbations of asthma, chest wall deformation, mucus plugging during artificial ventilation, diaphragmatic dysfunction, decreased chest excursion post

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surgery and mucus plug during artificial ventilation are all scenarios during which atelectasis may occur. Airway clearance techniques are contra-indicated for atelectasis secondary to foreign body aspiration, since the foreign body may displace to the central airways with resultant choking [26]. A surgical procedure requiring general anaesthesia and artificial ventilation interferes with normal lung clearance and, together with postoperative pain and impaired breathing mechanics, is a risk factor for atelectasis. The rationale for using airway clearance techniques in the post operative period is, thus, certainly there. But the outcome of one study using prophylactic postural drainage and vibration in children, post cardiac surgery is disappointing; treatment was associated with significantly more frequent and more severe atelectasis [30]. A few recent studies report on the use of intrapulmonary percussive ventilation via a face mask to treat atelectasis. The percussive ventilator delivers mini bursts of highvelocity airflow superimposed on the patient’s spontaneous respiratory cycle. During this technique, the highest peaks of pressure are reached at the beginning of expiration. These pressure peaks create a percussive effect with the aim to break up mucus plugging and enhance deep and homogeneous ventilation of the lungs. A prospective randomised controlled clinical trial in intubated and ventilated children with atelectasis at a mean age of 3 years compared the use of intrapulmonary percussive ventilation with chest clapping and vibration. Atelectasis improved in the percussive ventilation group but not in the group receiving chest clapping and vibration [11]. A case series reports the treatment of atelectasis of unknown cause in acutely dyspnaeic Vietnamese children by intrapulmonary percussive ventilation via a face mask over 5 days. The intervention was reported to be safe and effective in resolving the atelectasis in three of the four children [37]. The main problem with studies evaluating airway clearance techniques as a treatment for atelectasis is the lack of a homogeneous patient group; the mechanism of atelectasis and, thus, the optimal treatment strategy likely differs between patients. From a physiological point of view, the use of positive end-expiratory pressure could benefit children with partial airway obstruction due to secretions. Whether the use of a positive end-expiratory pressure face mask or flutter improves airway patency and peripheral airway clearance in real life has not been proven outside the context of cystic fibrosis [27].

Children treated with mechanical ventilation Two decades ago, chest physiotherapy was considered to be the standard therapy in mechanically ventilated patients

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beyond the newborn period. A more critical evaluation revealed that manual chest percussion in ventilated patients is a stressful procedure, causing an increase in oxygen consumption and an elevation in the heart rate, blood pressure and intracranial pressure [19, 24]. One should be even more critical about applying airway clearance techniques in ventilated children compared to adults because of their very compliant chest wall [14]. For a review of the topic, Krause and Hoehn can be consulted [21].

Dysfunctional breathing, vocal cord dysfunction, hyperventilation, habit cough Hyperventilation, as well as vocal cord dysfunction syndrome, can be confused with asthma. In both conditions, refractoriness to asthma treatment can lead to an escalation in asthma medication until the correct diagnosis is made [28, 35]. Hyperventilation as a cause of pseudo asthma is well known by physicians, as well as lay people. Attacks are probably triggered by anxiety. The complaint of shortness of breath is accompanied by dizziness, palpitations and faintness. There is less general awareness about the “vocal cord dysfunction syndrome,” a functional disorder due to recurrent attacks of paradoxical adduction of the vocal cords during inspiration. These attacks occur spontaneously or can be associated with strenuous aerobic exercise in young athletes. To complicate matters, both syndromes can occur concurrently with genuine asthma. A chronic, loud, honking or barking cough that persists during the day but is absent when the child sleeps should alert to the possibility of a habit cough, also called psychogenic cough or cough tic. All of these disorders are mainly behavioural. The first task is to make a correct diagnosis at an early stage and to have this diagnosis accepted by the parent and child, thereby, protecting the child against further invasive, costly and possibly damaging investigations. There are no good data on the optimal treatment of these conditions. In functional disorders associated with increased anxiety, it seems obvious to reassure the parent and child, and, if needed, to bring in relaxation techniques, behavioural therapy and even “self-hypnosis” and breathing techniques [2, 35]. Which specific paramedical person will be involved in this type of disorder may vary; physiotherapist, speech therapist or other. There are no randomised trials evaluating these treatments for these disorders. We, as others [2, 35], have a positive experience with relaxation therapies and breathing exercises for hyperventilation and vocal cord dysfunction and with “positive feedback” to teach selfcontrol in the case of habit cough. The long-term outcome for these children is not well known. Most seem to do well

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[12], but it is possible that a least some of them will continue to suffer from functional disorders during adult life.

Harm from airway clearance techniques? There is no evidence that a clear benefit is obtained from using airway clearance techniques in a previously healthy child with an acute respiratory disorder. In case a physician does prescribe these therapies, particular care must be taken to be certain that one does not inflict any harm. Due to a very compliant and, thus, highly unstable chest wall, infants are prone to atelectasis and respiratory insufficiency. Positioning serves to redistribute ventilation, but the young infant’s response to the forces of gravity differs substantially from that of the adult [10]. When lying on their side, an infant breathes with the uppermost lung, whereas an adult will preferentially ventilate the dependent lung. Also, the infant’s airway wall is more labile and airway hyperresponsiveness is elicited easily [9]. In young children, peripheral airway resistance is high and dynamic compression of peripheral airways during forced expiration is a particular problem [38]. For all of these reasons, it is not surprising that some case reports on “chest physiotherapy” in infants feature decreased oxygen saturation, increased oxygen consumption, gastro-oesophageal reflux, fractured ribs, raised intracranial pressure and even brain injury [17]. Too few studies assess the newer airway clearance techniques; it is not impossible that they offer a better balance between efficacy and risk of inflicting harm. Another reason for not prescribing airway clearance techniques in children with acute respiratory disorders is the wasting of the time and effort of expert physiotherapists and their time taken away from the care of children with chronic disease who will likely benefit, i.e. children with suppurative lung disease (cystic fibrosis, primary ciliary dyskinesia, bronchiectasis) and children with neuromuscular disease who have restrictive lung disease and ineffective cough.

Absence of evidence is not evidence of absence... The fact that “on the whole” airway clearance techniques do not benefit children with acute respiratory disease does not mean that not a single individual child with acute respiratory disease can ever benefit from it. To select “exceptional” children in whom therapy may be indicated, general principles can be taken into account. Is there a sound rationale to prescribe an airway clearance technique in this individual patient, e.g. does he/she seem to have particular problems clearing secretions (because of fatigue,

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weight loss etc.) and do these secretions likely contribute to increased work of breathing or gas exchange disturbance? Will the patient tolerate treatment or are side effects likely? In patients passing this positive selection, a trial session(s) may be indicated with a critical appraisal on an individual basis. And certainly in these selected cases, good communication between the physician and chest physiotherapist is crucial. The physician routinely or “frequently” prescribing airway clearance techniques in previously healthy children with acute respiratory disease should question their practice.

Other possible tasks for the physiotherapist in the care for children with acute respiratory disorders The main role of chest physiotherapists will be the care of children with chronic disorders, such as cystic fibrosis, neuromuscular disease, primary ciliary dyskinesia and immunodeficiency. Many chest physiotherapists working in paediatric hospitals are experts at inspecting children’s chest wall motions and breathing patterns. This fact likely explains why chest physiotherapists are often “popular” with the parents of children with an acute respiratory illness; they come into their home, offer security, reassure the parents etc. The special expertise of physiotherapists make them ideal candidates to take on specific tasks in the care for the general paediatric patient with acute respiratory disease. Teaching and supervising the correct inhalation therapy of asthma drugs with nebulisers, spacers and dry powder inhalers, instructing about the hygienic use of inhalation material, awareness about environmental contamination due to inhalation therapy, principles of oxygen therapy and other tasks can be taken on by physiotherapists, especially in settings where asthma nurses and/or respiratory therapists are not available.

Conclusion Airway clearance techniques are often prescribed in previously healthy children with an acute respiratory disorder. Research into this area is limited. The reasons for this are multiple; difficulty in defining homogeneous patient groups, many different devices and techniques are used in different combinations, large variability in operator expertise, near-impossibility to define comparison treatments or blind control groups. The studies that have been carried out do not support a standard add-on of airway clearance techniques in previously healthy children with an acute respiratory disease. Nearly all children with normal

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lung defence mechanism and normal chest wall function recover completely after an acute respiratory illness. Therefore, it is very unlikely that airway clearance techniques will bring about a long-term benefit. They will, however, substantially add to the treatment cost. Physicians who continue to routinely prescribe airway clearance techniques in patients with bronchiolitis, pneumonia and acute asthma should question their practice.

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