Effect of airway inflation pressure on forced expiratory maneuvers from raised lung volume in infants*

AbstractThe raised lung volume technique is increasingly used to measure forced expiratory maneuvers in infants. However, there is no consensus regarding the optimal airway inflation pressure (Pinf) required for such maneuvers, or the influence of small changes in Pinf within and between infants. The aim of this study was to assess the effect of small differences (0.2–0.3 kPa) in Pinf on forced vital capacity (FVC), forced expired volume in 0.5 sec (FEV0.5), and forced expired flow at 75% of vital capacity (FEF75), all derived from the raised volume rapid thoraco‐abdominal compression (RVRTC) technique. Randomized paired forced expiratory maneuvers were obtained in 32 healthy infants ( 3.9–39.3 weeks old, 3.8–9.9 kg) with the safety pressure relief valve for Pinf set to 2.7 kPa or 3.0 kPa (27 or 30 cm H20).When mean (SD) Pinf was increased by 8.4 (2.8)%, there was a significant (P < 0.01) increase in mean (SD) FVC, FEV0.5, and FEF75 by 5.8 (5.7)%, 6.1 (6)%, and 8.3 (16.2)%, respectively.In conclusion, relatively small differences in Pinf will result in significant differences in FVC, FEV0.5, and FEF75 by RVRTC technique. Precision in setting and reporting the applied Pinf is therefore essential, particularly if data are to be compared between centers. Pediatr Pulmonol. 2002; 33:130–134. © 2002 Wiley‐Liss, Inc.