Gas Exchange During Maximal Upper Extremity Exercise: Discussion (6)
Another possible explanation for the large difference between P(A-a)02 responses is that diffusion does not limit 02 exchange during maximal arm crank, but may, as has been suggested by Dempsey et al, limit exchange during exhaustive lower extremity exercise. Wagner and associates began to appreciate a diffusion component to the P(A-a)02 during leg exercise performed at sea level, when Vo2 was greater than 30 ml/ kg/min. Our subjects exercised at 1,270 m, but Vo2 was only 31 ml/kg/min during maximal arm crank exercise, compared to 45 ml/kg/min during cycle exercise (Table 2). Probably the level of Vo2 during arm crank exercise was not sufficiently high to result in a diffusion limitation. However, the persistence of a greater P(A-a)Oa during leg exercise vs arm crank exercise at a comparable level ofVo2 (Table 3) suggests that factors other than differences in Vo2 may also be operative. However, with the data from the present study, further speculation about mechanisms is not possible. buy cheap antibiotics
The PaC02 during peak arm crank exercise was similar to that during peak cycle exercise while pH was significantly higher (Table 3). In contrast, Sawka and associates found lower levels of Pco2 for arm crank exercise compared to leg exercise with similar values for pH. In that study, the same subjects were used for both arm crank and cycle exercise; thus, their study was better controlled.