CO2 chemosensitivity during immersion in humans.
Hypercapnic ventilatory response was compared in 9 seated subjects during head-out immersion in 35 degrees C (thermoneutral) water and during non-immersion in 28 degrees C (thermoneutral) room air. Using Read's CO2-rebreathing technique, minute ventilation (VE) and end-tidal (ET) PCO2 were sampled continuously for 4-5 min with a spirometer and a mass spectrometer, while the subject rebreathed a 6 L gas mixture initially containing 7% CO2 and 93% O2 in a bag-in-box system. The slope of the hypercapnic ventilatory response curve, expressed as delta VE/delta PETCO2, ranged from 0.76 to 2.49 L/min/mmHg. Immersion affected neither the slope nor the position of the hypercapnic ventilatory response curve. The rate of rise of PETCO2 during immersed CO2-rebreathing was significantly reduced (4.47 +/- 0.19 [SE] mmHg/min), as compared to the control value (5.67 +/- 0.24). It was concluded that the CO2 chemosensitivity during immersion in humans did not change and that the capacity to store CO2 in tissue might have been increased.
Department of Hyperbaric and Diving Medicine, Naval General Hospital, Tsoying, Taiwan, R.O.C.
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LP
Chang
C E
CE
Lundgren
D000280:Administration, Inhalation; D000328:Adult; D000388:Air; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007101:Immersion; D008297:Male; D013058:Mass Spectrometry; D010313:Partial Pressure; D012119:Respiration / Q000187:drug effects; D013147:Spirometry; D013696:Temperature; D013990:Tidal Volume
D002245:Carbon Dioxide