Increased Airway Hyperreactivity with the M40 Protective Mask in Exercise-Induced Bronchospasm

Objective. Exercise-induced bronchospasm (EIB) has a prevalence of 6% to 7% in United States Army personnel and 3% to 13% in professional athletes. There are reported concerns that military personnel with EIB will have increased airway hyperreactivity or significant dyspnea while wearing the standard military M40 protective mask. The objective of this study is to determine whether the M40 protective gas mask increases airway hyperreactivity in military personnel with exertional dyspnea and the diagnosis of EIB. Methods. Ten active duty military with EIB (defined as history of exertional dyspnea, normal spirometry, and reactive methacholine challenge test) and 10 normal control subjects were evaluated. Both the participants and control subjects underwent baseline exercise challenge testing (ECT) with and without the M40 protective mask. Forced expiratory volume in one second (FEV₁) (percent predicted) post ECT was compared to baseline FEV₁ within and between groups along with exercise time. Results. There was no statistical difference in between individuals and between groups wearing the M40 mask. None of the study group had a positive ECT exercising without the M40 mask while 20% of the study group with EIB had a positive ECT wearing the M40 mask. Conclusion. Military personnel with EIB who exercised with the M40 protective mask did not overall have significantly increased airway hyperreactivity compared to control subjects. Screening ECT may be beneficial in identifying those susceptible persons who report symptoms while wearing the M40 protective mask.