Abstract

Background: Inhalation of hypertonic or even isotonic saline during sputum induction may cause bronchospasm in susceptible patients with asthma, despite premedication with 400 µg inhaled salbutamol delivered by pressurised metered dose inhaler (pMDI). The bronchoprotection afforded by additional inhaled salbutamol administered through the ultrasonic nebuliser during sputum induction was investigated.

Methods: Twenty patients with moderate to severe asthma underwent sputum induction by inhaling saline 4.5% (or 0.9% if post-bronchodilation forced expiratory volume in 1 second (FEV₁) <65% predicted) for 10 minutes according to two protocols given 1 week apart in random order. At visit A the patients received 400 µg salbutamol administered through a pMDI + spacer 20 minutes before induction while at visit B the premedication was supplemented by 1500 µg nebulised salbutamol inhaled throughout the induction procedure. Both the investigator and the patients were blind to the nebulised solution used. FEV₁ was recorded during sputum induction at 1, 3, 5, and 10 minutes. Sputum cell counts and histamine, tryptase and albumin levels in the supernatants were determined.

Results: The mean (SE) maximal reduction in FEV₁ over the 10 minute period of sputum induction was 11.7 (2.8)% at visit A, which was significantly greater than at visit B (2.6 (1.2)%; mean difference 9% (95% CI 2.7 to 15.4), p<0.01). Total and differential sputum cell counts as well as albumin, tryptase, and histamine levels did not differ between the two visits.

Conclusion: The addition of inhaled salbutamol through an ultrasonic nebuliser markedly improves bronchoprotection against saline induced bronchoconstriction in patients with moderate to severe asthma undergoing sputum induction without affecting cell counts and inflammatory markers.