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.
Chang
L P
LP
Department of Hyperbaric and Diving Medicine, Naval General Hospital, Tsoying, Taiwan, R.O.C.
Lundgren
C E
CE
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