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PREDICTIVE STUDIES VII (PS VII): Interactions of Hyperoxia, Exercise, and Immersion in Neurologic O2 Poisoning.
Major Category: Oxygen toxicity and oxygenation. Immersion. Exercise. (PS VII)
Subcategory 9: Partial and total immersion and hypercapnia

Stressors: immersion, hypercapnia

Date: 1993

Expt. Title: Effects of partial and total immersion on physiological responses to progressive hypercapnia while breathing O2 at 1.0 ATA. (Expt. 13.01, 13.02, 13.03).

Description:

This was the first investigation using improved methods of holding the TCD probe in place without excessive pressure on the side of the skull, of eliminating interference with the TCD signal during full immersion and of regulating back pressure in the breathing system during immersion. Eight Subjects were studied at rest in the dry condition, then during head-out immersion, and finally during total immersion. Water temperature was kept at 35^o C. In each condition, the subject first breathed air, then 100% O2. This was followed by consecutive periods breathing elevated levels of CO2, controlled so that end-tidal PCO2 was maintained at 45, 50 and 55 mm Hg. The subject was connected to the gas delivery and elimination systems by a low resistance (Hans Rudolph, "T" configuration valve assembly using tricuspid check valves). Two paralleled inspiratory demand regulators were adjusted in the water column to deliver inspired gas at pressure to balance the water column acting on the subject’s lungs. This pressure was maintained in the airway with an adjustable back pressure regulator at the expiratory end of the airway.

Measurements:

Arterial and end-tidal CO2 tensions, arterial PO2 and pH, inspired CO2 concentration, airway pressure, ventilation and respiratory frequency, tidal volume, water and body temperatures, systolic, diastolic and mean arterial blood pressures, heart rate, MCA blood flow velocity.

REPORT: Clark, J.M., R. Gelfand, G. Beck, Jr., B.A. Youdelman, E.J. Hopkin, and C.J. Lambertsen. Effects of head-out and total immersion at 1.0 ATA on ventilatory and cerebral circulatory responses to progressive hypercapnia (ABSTRACT). Undersea and Hyperbaric Med. 21 (S):36, 1994.

07 February 2000 11:09:02 AM