BRONCHODILATOR RESPONSIVENESS TESTING USING RAISED VOLUME FORCED EXPIRATION IN RECURRENTLY WHEEZING INFANTS

We hypothesized that a new test of infant lung function, less affected by shifts in lung volume, might better detect bronchodilator effects. Using the raised volume forced expiration technique (RVFET), the effe ct of a bronchodilator on lung function was studied in 22 infants with a history of recurrent wheeze and five healthy infants. Forced expira tory volume in 0.75 s (FEV0.75), forced expiratory vital capacity (FVC ), and forced expiratory flow at 75% of FVC (FEF75%) were measured by forcing expiration, using an inflatable jacket from a lung volume set by an inspiratory pressure of 20 cm H2O. A minimum of five measurement s were made at baseline and following the administration of 500 mu g o f salbutamol from a metered dose inhaler via a small volume metal spac er. Changes in lung function in the group of 25 infants who received s albutamol were compared to seven infants who received placebo aerosol. No significant changes occurred in measures of lung function followin g salbutamol administration when compared to baseline or placebo despi te a significant increase in heart rate. A shift in lung volume is unl ikely the reason why infants do not demonstrate a change in forced exp iration following bronchodilator administration. Pediatr Pulmonol. 199 8; 26:35-41, (C) 1998 Wiley-Liss, Inc.