The influence of the self-contained breathing apparatus (SCBA) on ventilatory function and maximal exercise

Our previous work showed that breathing low density gases during exercise with the self-contained breathing apparatus (SCBA) improves maximal ventilation (E) and maximal oxygen consumption (<(V)over dot>O(2)max). This suggests that the SCBA limits exercise by adding a resistive load to breathing. In this study we compared <(V)over dot>O(2)max with and without the various components comprising the SCBA to determine their impact on <(V)over dot>O(2)max. Twelve males performed 4 randomly ordered incremental exercise tests to exhaustion on a treadmill: (1) low-resistance breathing valve only (CON); (2) full SCBA (SCBA); (3) SCBA regulator only (REG); and (4) carrying the cylinder and harness assembly but breathing through a low-resistance breathing valve (PACK). Compared to CON, <(V)over dot>O(2)max was reduced to a similar extent in the SCBA and REG trials (14.9% and 13.1%, respectively). The PACK condition also reduced <(V)over dot>O(2)max, but to a lesser extent (4.8 +/- 5.3%). At <(V)over dot>O(2)max, <(V)over dot>E was decreased and expiratory mouth pressure and external breathing resistance (BR) were increased in both the SCBA and REG trials. There was a significant correlation between the change in maximal <(V)over dot>(E) and <(V)over dot>O(2)max with the SCBA. The results show that the SCBA reduces <(V)over dot>O(2)max by limiting <(V)over dot>(E) secondary to the increased BR of the SCBA regulator.