Purpose: Protective self-contained breathing apparatus (SCBA) used for firefighting delivers decompressed (cold), dehumidified air that may enhance the severity of exercise-induced bronchoconstriction (EIB) in those susceptible. We investigated the effect of SCBA during exercise on airway caliber in people with asthma and healthy controls.
Methods: Two exercise challenges (EC) designed to elicit EIB were performed on separate days within one week. The initial challenge was breathing room air (ECRA) with workload titrated to elicit >60% estimated maximum voluntary ventilation. The exercise intensity was repeated for the second challenge using SCBA (ECSCBA). Forced expiratory volume in one second (FEV1) was measured before and up to 20min after exercise. Bronchial hyperresponsivenss (BHR) to the hyperosmolar mannitol test was measured in the subjects with asthma.
Results: Twenty subjects with current asthma (mean[SD] age 27 years) and 10 healthy controls (31 years, p=0.1) were studied. The % fall in FEV1 following ECSCBA was greater in the mannitol positive asthma subjects (14.4 [15.1]%) compared to mannitol negative asthmatic subjects (1.6 [1.7]%, p=0.02) and controls (2.3 [2.3]%, p=0.04). The FEV1 response was not different between ECRA and ECSCBA (0.49 [5.57] %, p=0.6). No BHR to mannitol (n=7) was highly sensitive for identifying a negative response to ECSCBA (negative predictive value 100%).
Conclusions: SCBA does not increase the propensity or severity for EIB in subjects with BHR. Those subjects with asthma but no BHR to inhaled mannitol did not exhibit EIB. BHR to a hyperosmolar stimulus maybe considered a useful screening tool for potential recruits with a history of asthma.
(C) 2017 American College of Sports Medicine