Citation

Gill M, Natoli MJ, Vacchiano C, Macleod DB, Ikeda K, Qin M, Pollock NW, Moon RE, Pieper C, Vann RD. J. Appl. Physiol. (APS Bethesda) 2014; 117(4): 406-412.

Affiliation

Duke University Medical Center rvann@dan.org.

Copyright

(Copyright © 2014, American Physiological Society)

DOI

10.1152/japplphysiol.00995.2013

PMID

24947022

Abstract

Hyperoxia during diving has been suggested to exacerbate hypercapnic narcosis and promote unconsciousness. We tested this hypothesis in male volunteers (12 at rest, 10 at 75 W cycle ergometer exercise) breathing each of four gases. Inspired PO2 (PIO2) was 0.21 and 1.3 atmospheres (atm) without or with an individual subject's maximum tolerable inspired CO2 (PICO2 = 0.055-0.085 atm). Measurements included end-tidal CO2 partial pressure (PETCO2), rating of perceived discomfort (RPD), expired minute ventilation (VE), and cognitive function assessed by auditory n-back test. The most prominent finding was, irrespective of PETCO2, that minute ventilation was 8-9 Lpm greater for rest or exercise with a PIO2 of 1.3 atm compared to 0.21 atm. When breathing 1.3 atm PIO2, resting subjects (but not exercising subjects) experienced more discomfort (RPD) at lower values of PETCO2 but not at higher PETCO2. PIO2 did not significantly affect the relationship of n-back score to PETCO2. Subjects completed 66 hyperoxic hypercapnic trials without incident, but five subjects stopped prematurely due to serious symptoms (tunnel vision, vision loss, dizziness, panic, exhaustion, or near-syncope) during 69 normoxic hypercapnic trials (p=0.0582). Serious symptoms during hypercapnic trials occurred only during normoxia.

Language: en