Analysis of expiratory pattern for monitoring bronchial obstruction in school‐age children

This study was designed to assess the validity of the percent of volume expired at tidal peak flow (dV/V t ) as an indicator of bronchial obstruction in school‐age children. We analyzed 126 dV/V t ratios and compared them with spirometric and plethysmographic results measured in 24 healthy (14 males) and 60 asthmatic (41 males) children; 42 of them underwent measurements before and after bronchial challenge with histamine. The two groups differed in resistance, forced expiratory volume in 1 sec (FEV 1 ), and forced expiratory flows, as percents of predicted (FEV 1 : 94.6 ± 2.4% in controls vs 86.7 ± 1.6% in asthmatics; P <0.001). They did not differ in peak expiratory flow (PEF), forced vital capacity, functional residual capacity, measured by body plethysmography, and in d/V t . The dV/V t was found to correlate with FEV 1 ( r =0.58, P <0.001), PEF ( r =0.57, P <0.001), and other lung function parameters. Forty‐two of the asthmatic children performed a bronchoprovocation histamine test. The fall of dV/V t after histamine was significantly correlated ( r =0.61, P <0.001) with the variation in FEV 1 and other lung function parameters. We conclude that dV/V t is a good indicator of bronchial obstruction, as useful in school‐age children as in adults and infants, with no need for the subject's cooperation. Pediatr Pulmonol 1991; 10:6–10.