Bronchoconstriction induced by spirometric maneuvers in patients with bronchial asthma

We analyzed forced expiration maneuver-induced bronchoconstriction in 14 asthmatic patients and in seven normal subjects by breaking down the forced expiration maneuver of spirometry (the FVC maneuver) into two phases: a slow, deep inspiration to the total lung capacity (TLC) (the DI maneuver) and a forced expiration to the residual volume (RV) (the PFV maneuver). Specific airway conductance (sGaw) was measured at functional residual capacity (FRC) after each of the three maneuvers. All of the maneuvers caused the greatest bronchoconstriction immediately after completion of the maneuver. The mean decreases in the sGaw immediately after the FVC, DI, and PFV maneuvers were 45.0 +/- 6.6 (SD)% (P less than .001), 29.6 +/- 5.3% (P less than .001), and 16.7 +/- 5.3% (P less than .03), respectively. The decrease in sGaw by the FVC maneuver was very close to the combined algebraic sum of the DI maneuver and the PFV maneuver. The normal subjects did not show any changes in the sGaw by any of the maneuvers. The inhalation of albuterol almost abolished the response of bronchoconstriction to any of the three maneuvers, but inhalation of an anticholinergic agent, ipratropium bromide, did blunt the response. This study suggests that forced expiration maneuver-induced bronchoconstriction in asthmatics can be caused not only by deep inspiration to the TLC but also by forced expiration to the RV, and that the bronchoconstriction may be brought about mainly by an increase in parasympathetic activity.