Oxygen-Enhanced Breath-hold Diving, Phase I: Hyperventilation and Carbon Dioxide Elimination.

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Oxygen-Enhanced Breath-hold Diving, Phase I: Hyperventilation and Carbon Dioxide Elimination.

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Title: Oxygen-Enhanced Breath-hold Diving, Phase I: Hyperventilation and Carbon Dioxide Elimination.
Author: Pollock, NW; Vann, RD; Thalmann, ED; Lundgren, CEG
Abstract: Hyperventilation (HV) is commonly used to extend breath-hold time by eliminating carbon dioxide to delay the hypercapnic stimulus to end breath-hold. The chief hazard is that loss of consciousness may result from hypoxia before the hypercapnic drive initiates a breathing cycle. The purpose of this study is to evaluate the efficacy of oxygen inspiration to improve the safety of breath-holding techniques. Phase I evaluates the effect of different HV rates on end-tidal carbon dioxide concentration (PetCO2) and whole body elimination of carbon dioxide. Eleven healthy, fit individuals (10 male, ane female) completed three rounds of 60 s of HV at the following rates: 10, 15, 20, 25, 30, and 35 breaths/min. Individual performance was not difficult to regulate and stable from trial to trial. The metabolic cost of HV was higher than expected, with mean "bonus elimination" of carbon dioxide between 200-1000 mL. End-HV PetCO2 was negatively correlated with HV rate (r=0.688; p=<0.05) while end-HV sum of symptom scores was positively correlated (r=0.314; p=<0.05). Based on the Phase I experience, the HV rate of 20 breaths /min is accepted as optimal for 60 s of HV in terms of subjective comfort, ensuring that end-HV PetCO2 remains above 20 torr(2.67 kPa) safe lower limit, and for ease of pacing.
Description: American Academy of Underwater Sciences (http://www.aaus.org/)
URI: http://archive.rubicon-foundation.org/4647
Date: 1997

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