OBJECTIVEAfter performed symptom-limited maximum cardiopulmonary exercise testing (CPET) before and after acute alkalized blood, we repeated CPET with pure oxygen.

METHODSFive volunteers, 3hr after alkalizing blood room air CPET, re-performed CPET inhaling from Douglas bag connected with pure oxygen tank. We compared with those of room air CPETs before and after alkalized blood.

RESULTSAfter alkalized blood oxygen CPET had a similar response pattern as those of CPETs before and after blood alkalization. During the CPET, all breath frequency, minute ventilation and tidal volume at each stage were similar to those of CPETs before and after alkalized blood (P > 0.05),except there was a lower peak tidal volume than those of both CPETs and a slightly higher resting minute ventilation only than CPET after alkalized blood (P > 0.05). After alkalized blood, oxygen CPET, all PaO2 and SaO2 and most Hb were lower than those of both CPETs (P < 0.05). The pHa and [HCO3-]a were higher than those of CPET before alkalized blood (P < 0.05); but were not CPET after alkalized blood (P > 0.05). PaCO2 was similar to that of CPET before alkalized blood (P > 0.05), but was lower than that of CPET after alkalized blood at resting and warm-up (P < 0.05); then was similar to both CPETs at anaerobic threshold (P > 0.05); but was higher at peak exercise higher than those of both CPETs (P < 0.01). Oxygen increased 2,3 volunteers' workload and time at AT and peak exercises.

CONCLUSIONRespiratory response pattern to oxygen CPET after alkalized blood is similar to those of both CPETs before and after alkalized blood. The CPET response is dominantly depended upon metabolic rate, but not levels of pHa, PaCO2 and PaO2.