Prolonged slow expiration technique in infants: effects on tidal volume, peak expiratory flow, and expiratory reserve volume.

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.