Effect of hyperoxia on performance capacity of firemen.

We examined the effect of O2-enriched air upon performance capacity and some physiological and psychological variables. Eight firemen were studied during seven bouts of 2 min treadmill-running while breathing air with 21 or 40% oxygen. The duration of the resting periods between the working bouts was chosed by the subjects themselves, with the instructions to rest as short as possible. Total resting time decreased by 29% and total amount of air used by 6%, under the 40% oxygen condition. There were no differences in 1) minute ventilation during working periods (when the subjects breathed 40% oxygen respiratory rate decreased whereas tidalvolume increased), 2) heart rate reached during working periods, 3) subjective feelings of fatigue as indicated by the subjects at the end of every working period. Advantages of the use of O2-enriched air by firemen are discussed and it is concluded that breathing air with 40% oxygen does not mean an extra physiological or psychological load for the organism. Finally, possible factors that made a subject decide to start again are discussed and the importance of the respiratory rate in this decision is indicated.