Comparison of terbutaline, isotonic saline, ambient air and non-treatment in patients with reversible chronic airway obstruction.

The increase in forced expiratory volume in one second (FEV1) seen in asthmatics after inhalation of isotonic saline was studied in a blind, cross-over investigation of 24 consecutive out-patients presenting with reversible chronic airway obstruction. Forced expiratory manoeuvres allowing the measurement of FEV1 and forced vital capacity (FVC) were performed at six time intervals during a period of one hour according to the following regimes: inhalation of terbutaline by means of a Pari-inhalier Boy for 10 min; inhalation of isotonic saline under the same conditions; inhalation of ambient air under the same conditions (placebo with noisy nebulizer); inhalation of air without the nebulizer (non-treatment) in order to determine whether the impact of treatment by a nebulizer influences the measured lung function. A statistically significant increase in FEV1 was observed after each of the four regimes. The increase was large following terbutaline inhalation. After the other three regimes, it was significantly smaller and of about the same magnitude in each case. The increase in FEV1 after the non-treatment regime was unexpected and could possibly be due to the repeated dynamic spirometry. The increase in FEV1 after isotonic saline and ambient air (noisy nebulizer) did not differ from the increase after the non-treatment regime. We conclude that neither isotonic saline nor the impact of treatment with a noisy nebulizer have a measurable effect on lung function.