Respiratory Responses during Exercise in Self-contained Breathing Apparatus among Firefighters and Nonfirefighters.

Background: Firefighters are required to use self-contained breathing apparatus (SCBA), which impairs ventilatory mechanics. We hypothesized that firefighters have elevated arterial CO2 when using SCBA.

Methods: Firefighters and controls performed a maximal exercise test on a cycle ergometer and two graded exercise tests (GXTs) at 25%, 50%, and 70% of their maximal aerobic power, once with a SCBA facemask and once with protective clothing and full SCBA.

Results: Respiratory rate increased more in controls than firefighters. Heart rate increased as a function of oxygen consumption ( V . O 2 ) more in controls than firefighters. End-tidal CO2 (ETCO2 ) during the GXTs was not affected by work rate in either group for either condition but was higher in firefighters at all work rates in both GXTs. SCBA increased ETCO2 in controls but not firefighters.

Conclusions: The present study showed that when compared to controls, firefighters' hypoventilate during a maximal test and GXT. The hypoventilation resulted in increased ETCO2 , and presumably increased arterial CO2 , during exertion. It is proposed that firefighters have altered CO2 sensitivity due to voluntary hypoventilation during training and work. Confirmation of low CO2 sensitivity and the consequence of this on performance and long-term health remain to be determined.