Prolonged Slow Expiration Technique in Infants: Effects on Tidal Volume, Peak Expiratory Flow, and Expiratory Reserve Volume

Abstract

BACKGROUND: Prolonged slow expiration (PSE) is a physiotherapy technique often applied in infants to reduce pulmonary obstruction and clear secretions, but there have been few studies of PSE's effects on the respiratory system. OBJECTIVE: To describe PSE's effects on respiratory mechanics in infants. METHODS: We conducted a cross-sectional study with 18 infants who had histories of recurrent wheezing. The infants were sedated for lung-function testing, which was followed by PSE. The PSE consisted of 3 sequences of prolonged manual thoraco-abdominal compressions during the expiratory phase. We measured peak expiratory flow (PEF), tidal volume (V T ), and the frequency of sighs during and immediately after PSE. We described the exhaled volume during PSE as a fraction of expiratory reserve volume (%ERV). We quantified ERV with the raised-volume rapid-thoracic-compression technique. RESULTS: The cohort's mean age was 32.2 weeks, and they had an average of 4.8 previous wheezing episodes. During PSE there was significant V T reduction (80 ؎ 17 mL vs 49 ؎ 11 mL, P < .001), no significant change in PEF (149 ؎ 32 mL/s vs 150 ؎ 32 mL/s, P ‫؍‬ .54), and more frequent sighs (40% vs 5%, P ‫؍‬ .03), compared to immediately after PSE. The exhaled volume increased in each PSE sequence (32 ؎ 18% of ERV, 41 ؎ 24% of ERV, and 53 ؎ 20% of ERV, P ‫؍‬ .03). CONCLUSIONS: It was possible to confirm and quantify that PSE deflates the lung to ERV. PSE caused no changes in PEF, induced sigh breaths, and decreased V T , which is probably the main mechanical feature for mucus clearance.

Effects of Manual Rib Cage Compressions on Expiratory Flow and Mucus Clearance During Mechanical Ventilation*

“…PSE is applied during the late phase of expiration up to the residual volume to improve interaction of the expiratory airflow with the mucus layer (23)(24)(25), specifically within the distal, narrower airways. The rational for its use is based on the evidence that airflows highly interact with mucus when the airways are narrower (7).…”

Chest physical therapy is effective in reducing the clinical score in bronchiolitis: randomized controlled trial

“…The actual physical therapy techniques are showed short-term benefits with PSE to some respiratory symptoms of bronchial obstruction in infants with AVB. The impact of this specific technique, in addition to the deflation of ERV is the increase in tidal volume resulting from subsequent activation of the Hering-Breuer reflex by a prolonged expiratory time and sighs [33][34][35] , which, in the infant, is clinically important because the inherent differences between the infant and adult making the respiratory system more likely to develop muscle fatigue and discomfort. Bernard-Narbonne et al 11 showed an increase in tidal volume and SpO 2 in the CP group of infants with AVB mechanical ventilation using slow expiratory flow as their technique of choice.…”

Chest Physical Therapy in Acute Viral Bronchiolitis: An Updated Review

“…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.…”