INHALED BETA-2-AGONIST AND POSITIVE EXPIRATORY PRESSURE IN BRONCHIAL-ASTHMA - INFLUENCE ON AIRWAY-RESISTANCE AND FUNCTIONAL RESIDUAL CAPACITY

Introduction: Positive expiratory airway pressure seems to dilate narr owed or collapsed airways, but this may be accompanied by a maintained and harmful increase in resting lung volume in obstructive pulmonary disease. Purpose: To evaluate the influence of inhaled terbutaline and positive expiratory pressure (PEP) on airway resistance (Raw) and fun ctional residual capacitv (FRC) in bronchial asthma. Design: Randomize d crossover design, single blind with regard to inhaled medication, op en with regard to PEP (PEP can be felt). Material and Methods: Ten pat ients with bronchial asthma inhaled placebo and terbutaline in doses o f 0.125 mg, 0.5 mg, and 1.5 mg by cone spacer combined with a facemask giving 0, 10, or 15 cm H2O PEP on separate days. FRC and Raw were mea sured by body plethysmography before and after inhalations. Data were analyzed by analysis of variance with terbutaline dose and PEP as fact or levels. Results: The effect of terbutaline: Raw decreased significa ntly (p<0.0001) after 0.125 mg and 1.5 mg. The FRC did not change sign ificantly. The effect of PEP: Raw decreased, but significantly only wh en the dose of 1.5 mg terbutaline was excluded from the analysis. Raw decreased with PEP 10 and 15 cm H2O, mean 0.6 (95 percent CI: -1.1, -0 .2) and 0.9 (95 percent CI: -1.3,-0.4) cm H2O/L/s. The FRC did not cha nge significantly with the PEP level. Conclusion: PEP only had influen ce on Raw when insufficient doses of terbutaline were inhaled, whereas once an efficient dose of terbutaline was administered, significant b ronchodilation was achieved with or without PEP. Positive expiratory p ressure did not increase FRC.