Impact of the prolonged slow expiratory maneuver on respiratory mechanics in wheezing infants *

OBJECTIVE To evaluate changes in respiratory mechanics and tidal volume (V T) in wheezing infants in spontaneous ventilation after performing the technique known as the prolonged, slow expiratory (PSE) maneuver. METHODS We included infants with a history of recurrent wheezing and who had had no exacerbations in the previous 15 days. For the assessment of the pulmonary function, the infants were sedated and placed in the supine position, and a face mask was used and connected to a pneumotachograph. The variables of tidal breathing (V T and RR) as well as those of respiratory mechanics-respiratory system compliance (Crs), respiratory system resistance (Rrs), and the respiratory system time constant (prs)-were measured before and after three consecutive PSE maneuvers. RESULTS We evaluated 18 infants. The mean age was 32 ± 11 weeks. After PSE, there was a significant increase in V T (79.3 ± 15.6 mL vs. 85.7 ± 17.2 mL; p = 0.009) and a significant decrease in RR (40.6 ± 6.9 breaths/min vs. 38.8 ± 0,9 breaths/min; p = 0.042). However, no significant differences were found in the variables of respiratory mechanics (Crs: 11.0 ± 3.1 mL/cmH2O vs. 11.3 ± 2.7 mL/cmH2O; Rrs: 29.9 ± 6.2 cmH2O • mL-1 • s-1 vs. 30.8 ± 7.1 cmH2O • mL-1 • s-1; and prs: 0.32 ± 0.11 s vs. 0.34 ±0.12 s; p > 0.05 for all). CONCLUSIONS This respiratory therapy technique is able to induce significant changes in V T and RR in infants with recurrent wheezing, even in the absence of exacerbations. The fact that the variables related to respiratory mechanics remained unchanged indicates that the technique is safe to apply in this group of patients. Studies involving symptomatic infants are needed in order to quantify the functional effects of the technique.