<bold>Purpose.</bold> Assessment of circulatory and respiratory response to separate exercise tests under the condition of increasing the volume of added respiratory dead space by 200 cm3 at a time. <bold>Basic procedures.</bold> Human volunteers performed 10 minutes of cycle ergometer exercise on nine occasions, with the increasing volume of added dead space at the intensity of 100 Watt. <bold>Main findings.</bold> The ventilatory parameters tended to increase proportionally to the volume of added dead space. VE, VT, RF increased from 29.35 ± 4.01; 1.62 ± 0.29; 18.52 ± 4.76 (at 0 cm3) to 62.42 ± 8.33; 2.43 ± 0.24; 26.00 ± 5.51 (at 1600 cm3), respectively. There were not any significant differences among the post-exercise values of LA, pO2, HCO-3act, BE(B) and HR. All the values of O2 SAT ranged between 94.87 ± 1.19 and 95.72 ± 0.76, and the values of HCO-3std between 25.23 ± 1.36 and 24.00 ± 0.78. The post-exercise values of pH decreased, and pCO2 increased proportionally to the volume of added dead space, from 7.41 ± 0.01 (at 0 cm3) to 7.33 ± 0.03 (at 1600 cm3) and from 40.89 ± 2.27 (at 0 cm3) to 51.13 ± 3.39 (at 1600 cm3), respectively. <bold>Conclusions.</bold> Added respiratory dead space evokes: increase in pulmonary ventilation, mainly in tidal volume; increase in arterial carbon dioxide pressure and decrease in pH, proportionally to the increase in dead space volume. Added dead space neither evokes hypoxemia nor intensifies anaerobic reproduction of ATP.
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