INSPIRATORY MANEUVER EFFECTS ON PEAK EXPIRATORY FLOW - ROLE OF LUNG ELASTIC RECOIL AND EXPIRATORY PRESSURE

We investigated the effects of two different inspiratory maneuvers (fa st or slow) on the ability of normal subjects to generate peak expirat ory flows (PEF) and maximal dynamic expiratory pressures (Pexp) during the performance of a forced vital capacity maneuver. During the fast maneuver (F), the subject inspired rapidly to total lung capacity (TLC ) and immediately performed a maximal expiration, whereas in the slow maneuver (S) the subject inspired slowly to TLC, paused for 4-5 s at T LC and then performed a maximal expiration. Ten normal subjects perfor med a series of such maneuvers. In addition to PEF and Pexp, we measur ed EMC activity of abdominal (EMGabd) and rib cage muscles, and lung e lastic recoil pressure (Pest). Overall, F yielded higher PEF values th an S (by approximately 7%); in addition, Pest, Pexp, rate of rise of P exp (dPexp/dt), and EMGabd were similarly higher with F than with S (p < 0.05 for all). Analysis of individual data showed that the interman euver differences in PEF were largely explained by differences in Pest , Pexp or dPexp/dt. Our data suggest that, in comparison with the slow maneuver, the fast maneuver induces a greater change in both the lung elastic recoil and expiratory muscle activation which account for dif ferences in PEF between the two maneuvers. The enhanced expiratory mus cle activation with the fast maneuver suggests a specific inspiratory- expiratory muscle interaction analogous to agonist-antagonist interact ions described for skeletal muscles.