HANA-KAI-II - 17-DAY DRY SATURATION DIVE AT 18.6 ATA .5. MAXIMAL OXYGEN-UPTAKE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 4  (3) , 283-296
Abstract
Cardiorespiratory responses of 4 men to submaximal and maximal cycling exercise were observed during 17 days at 18.6 ATA [atmospheres absolute pressure]. Inspired gas at pressure consisted of hyperoxic (PO2 [O2 partial pressure] = 232 mmHg) and normoxic (PO2 = 159 mmHg) He mixtures with relative gas densities of 3.8 and 2.8, respectively. The average of pre- and postdive .ovrhdot.VO2 max [maximum O2 consumption] (1 ATA air), which were not significantly different, was 3.10 l .cntdot. min-1. During 5 min of submaximal exercise at 50% of .ovrhdot.VO2 max, no significant difference in work rate, .ovrhdot.VO2, .ovrhdot.VCO2, .ovrhdot.VE [pulmonary minute ventilation] respiratory rate, heart rate (HR), stroke volume, blood pressures or rectal temperature was noted at 18.6 ATA compared to ATA with either gas mixture. Submaximal HR tended to decrease by 5 to 10 beats .cntdot. min-1 at pressure and in hyperoxia the .ovrhdot.VO2/HR ratio was significantly higher. Maximal exercise was performed to exhaustion at work rates requiring about 120% of .ovrhdot.VO2 max. Significant increases in .ovrhdot.VO2 max of 0.10 l .times. min-1 (3%) and in endurance time of 2 min (48%) were found during hyperoxic gas breathing, whereas normoxic values at 18.6 ATA were similar to those at 1 ATA. Significant reductions in maximal HR of 8 beats .cntdot. min-1 (4%) were observed with both gas mixtures at pressure and .ovrhdot.VE was significantly decreased by 36 l .cntdot. min-1 (26%) in hyperoxia and 29 l .cntdot. min-1 (21%) in normoxia. No change was found in the calculated cardiac output. Maximal voluntary ventilation, which was measured only for the hyperoxic gas, fell significantly by 80 l .times. min-1 (40%). Aerobic power and endurance performance were affected by O2 pressure. Normoxic work capacity was not decreased at 18.6 ATA, despite marked reductions in HR and .ovrhdot.VE.