Abstract
We describe the various therapies for infant acute viral bronchiolitis and the contradictory results obtained with chest physical therapy. The treatment target is bronchial obstruction, which is a multifactorial phenomenon that includes edema, bronchoconstriction, and increased mucus production, with a clinical grading defined as severe, moderate, or mild. Chest physical therapy is revisited in its various modalities, according to preliminary scoring of the disease.
Introduction
Acute viral bronchiolitis is the most common disorder and the leading cause of respiratory failure in infants (< 24 months of age). Respiratory syncytial virus is the most common pathogen (85%), but other organisms produce a similar clinical picture.1 The disease can be graded as severe, moderate, or mild, and for each presentation a score is applied, as proposed by Wang.2 The Wang clinical severity score is now prevailing in evaluating the treatment with hypertonic saline nebulization or chest physical therapy (CPT). The Wang clinical severity score has a good inter-observer agreement among caregivers, which is reinforcing its value.3–6
Severe bronchiolitis is characterized by retraction as well as inspiratory and expiratory wheezing, with a breathing frequency exceeding 60 breaths/min, and SpO2 < 90%. Nasal flaring, somnolence, and apnea can also be present; feeding is impossible. Hospitalization is required; minimal handling is the rule, and oxygen is needed, as well as intravenous hydration and, in some cases, mechanical ventilation. Currently, its treatment is supportive care.7 Noninvasive ventilation can be used as primary ventilatory support, or CPAP, used either alone or with heliox.8–10 In severe bronchiolitis the Wang clinical severity score ranges from 9 to 12.
In moderate bronchiolitis the breathing frequency ranges from 40 to 60 breaths/min, and SpO2 from 90% to 93%. Wheezing is mainly expiratory, with intercostal retraction and poor feeding ability. Supplemental oxygen and fluids per os are the mainstay of therapy. In moderate bronchiolitis the Wang clinical severity score ranges from 4 to 8.
In mild bronchiolitis the breathing frequency is < 40 breaths/min, with SpO2 ≥ 94%, end-expiratory wheezing, and absent or minimal retraction. Feeding is normal. Wang clinical severity score does not exceed 3. This is the most frequent presentation of bronchiolitis in infants, and the illness is self-limiting.
Physiopathology of Acute Viral Bronchiolitis
Bronchial obstruction is the end point of various lower respiratory tract diseases with an allergic or infectious etiology. Inflammation, which is the result of many pathological processes, triggers capillary dilation and extravasation of plasma into the bronchial wall leading to edema. Goblet cells hyperplasia develops, with excessive mucus production, resulting in narrowing or occlusion of the smaller airways, with ventilation dysfunction.11,12 Repeated episodes of bronchoconstriction may also lead to structural changes in the walls of the small airways, known as remodeling.13
Treatments in Acute Viral Bronchiolitis
Recommendations for management of acute viral bronchiolitis were published by the Subcommittee on Diagnosis and Management of Bronchiolitis in 2006.14
Medications
Currently there is no general agreement about medications. Bronchodilators, corticosteroids, and ribavirin are of little use.15,16 Antibiotics are indicated only in case of a bacterial complication.17 Nebulization of hypertonic saline is the treatment of choice for acute viral bronchiolitis, with reduction of the hospital stay and a better clinical score.18 Hypertonic saline has been validated and is reasonably safe.19 Adverse events, with coughing during nebulization, have been reported in 1% of cases, and bronchospasm in 0.3%.20 Hypertonic saline increases the surface liquid by its osmotic action on the submucosal edema, improves mucociliary function, and facilitates CPT maneuvers.21
Chest Physical Therapy
The aim of CPT is clearance of secretions and prevention of atelectasis and hyperinflation. The use of CPT in acute viral bronchiolitis has been debated for a long time, and the last Cochrane review concluded that CPT modalities (chest percussion, vibration in postural drainage positions, and forced expiratory techniques) do not improve the course of the disease in hospitalized infants with acute viral bronchiolitis.22 As a result, CPT in acute viral bronchiolitis is no longer recommended, but recent publications cast doubt on that conclusion.
Various terms have been used to describe the CPT clearance procedures: chest physical therapy, CPT, bronchial clearance technique, conventional CPT, bronchial drainage or hygiene, airway clearance maneuvers or techniques, increased-exhalation technique (in French, accélération, augmentation du flux expiratoire). However, the functional and mechanical features of CPT have not been investigated in infants.
In Anglo-Saxon countries, in the 1960s, CPT in adults and children was called forced expiratory technique, and was associated with postural drainage and clapping; it was referred to as conventional CPT.23 It was mainly used to treat cystic fibrosis in adolescents and adults. Conventional CPT was applied to facilitate mucus evacuation through gravity.24–26 However, it should be remembered that mucociliary clearance is predominant in the dependent lung areas of semi-sitting infants, as in adults, being stimulated by regional ventilation.27–29 No wonder that conventional CPT gives poor results and is poorly tolerated, with side effects such as esophageal reflux, tachypnea, tachycardia, hypoxemia, rib fracture, and severe central nervous system complications, especially in newborns.30–34 The 2012 Cochrane review showed no significant benefit from conventional CPT on clinical score or hospital stay, and conventional CPT in acute viral bronchiolitis is no longer recommended.35–37
In France, increased-exhalation technique has been widely used in various ways since the 1970s.38–40 A robust thoraco-abdominal pressure is applied to mimic the forced expiratory technique. Controlled studies have demonstrated no benefit from increased-exhalation technique on hospital stay or cardiorespiratory parameters in severe acute viral bronchiolitis.41–43 In addition, side effects have been observed (vomiting, transient respiratory dysfunction, bouts of hypotonia), requiring interruption of the procedure. Rib fracture and mechanical drawbacks such as tracheal collapse leading to air and secretion trapping have also been observed.44–47
It should be stressed that conventional CPT and increased-exhalation technique have been extrapolated from the adult or adolescent to the infant respiratory system. But the latter has a greater density of submucosal glands, more acidic mucus with a greater viscosity, a more compliant chest wall, a greater tendency for airways collapse, and no collateral ventilation. Thus young infants tolerate respiratory loads poorly and are susceptible to fatigue because of the immature pattern of their muscle fibers.48,49 This explains why conventional CPT and increased-exhalation technique can be detrimental, and why these methods are no longer recommended.
Recently, a passive slow expiratory maneuver has been proposed and called prolonged slow expiration technique.50 The maneuver is preceded by hypertonic saline nebulization, and has shown to have significant effects on clinical symptoms in moderate bronchiolitis and a cumulative day-to-day improvement.51 Prolonged slow expiration technique is safe and well tolerated, as it is more attuned to the infant's mechanical respiratory system. Prolonged slow expiration technique avoids bronchial collapse with its flow interruption. The prolonged slow expiratory phase during prolonged slow expiration technique exhales a significant portion of the expiratory reserve volume. The reduction in lung volume is associated with the protective reflex of the airways, which restores lung volume by sigh breathing (Hering-Breuer deflation reflex).52 As secretions reach the proximal airways, provoked cough takes over.
Another recent randomized controlled trial using the prolonged slow expiration technique and increased-exhalation technique maneuvers during the same session, in hospitalized acute viral bronchiolitis infants, did not demonstrate a more rapid return to clinical stability.53 Yet in this study there was a lack of stratification of the initial clinical severity score, and CPT was not preceded by hypertonic saline nebulization. Nevertheless, the authors noted a significant decrease of the respiratory score. CPT may delay or prevent the need for mechanical ventilation and may result in fewer complications, but the study was unable to demonstrate such outcomes, as the study did not have sufficient power.
Also, the Gajdos et al study41 and the Rochat et al study53 have identified patient subgroups whose auscultation was improved by this treatment. This improvement would be due to the absence of atopic background.
Another study comparing 3 CPT protocols in infants with acute viral bronchiolitis found clinical benefits for prolonged slow expiration technique and for conventional CPT, with longer benefits for prolonged slow expiration technique.54 At this point in time, a multicenter study would be needed to establish the usefulness of prolonged slow expiration technique preceded by hypertonic saline nebulization in moderate acute viral bronchiolitis.
Summary
CPT in acute viral bronchiolitis is mainly symptom-based. Edema is the first target of treatment, and hypertonic saline should precede the CPT maneuvers (Figure). Further controlled studies based on physiopathology and grading of bronchial obstruction should better define the indications and contraindications for CPT in acute viral bronchiolitis.
Algorithm for assessing indications and contraindications for chest physical therapy in acute viral bronchiolitis.
Acknowledgments
We thank Henri C Labasse MD, Department of Neurosciences, Grand Hôpital de Charleroi, Charleroi, Belgium, for assistance with translation.
Footnotes
- Correspondence: Guy Postiaux PT, Site Reine Fabiola, Avenue du Centenaire 73, 6061 Montignies-sur-Sambre, Charleroi, Belgium. E-mail: guy.postiaux{at}gmail.com.
The authors have disclosed no conflicts of interest.
Guy Postiaux presented a version of this paper at the meeting of the Associação Brasileira de Fisioterapia Cardiorrespiratória e Fisioterapia em Terapia Intensiva (ASSOBRAFIR), held May 16, 2012, in Rio de Janeiro, Brazil.
Supplementary material related to this paper is available at http://www.rcjournal.com.
- Copyright © 2013 by Daedalus Enterprises
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