Effects of deep inhalation during early and late asthmatic reactions to allergen

Eighteen asthmatic patients with a biphasic asthmatic reaction to house dust mite were studied. The effect of deep inhalation (DI) was quantitated by comparing the maximal expiratory flow at 40% (MEF40) of vital capacity from partial (P) and maximal (M) flow-volume curves, and specific airway conductance (SGaw) before and after DI (SGawDI). At baseline, the ratio MEF40M/P was significantly larger than unity (1.45 +/- 0.26 SD), whereas the ratio SGawDI/SGaw was not significantly different from unity (0.92 +/- 0.24). During early phase reaction, both MEF40M/P and SGawDI/SGaw were significantly increased to 2.66 +/- 0.97 and 1.96 +/- 0.47, respectively. During late phase reaction, when the FEV1 values were similar to those observed during early phase reaction, MEF40M/P and SGawDI/SGaw were 1.86 +/- 0.46 and 1.43 +/- 0.29, respectively, significantly higher than the values at baseline but significantly lower than those during early phase reaction. Similar results were obtained in a subgroup of nine patients when SGaw values during the late phase reaction were similar to those during the early phase reaction. We conclude that DI has a different effect during early and late asthmatic reactions, suggesting a different ratio of airway to parenchymal hysteresis. This may result from an increased parenchymal hysteresis (more peripherally located bronchial obstruction) or a decreased airway hysteresis (prominent airway inflammation) during the late phase reaction.