Hypercapnia: Cognitive Effects and Monitoring

Duke University58 enrolled

Overview

The investigators will simulate the conditions of a working, helmeted diver by using exercising, "head out" immersed subjects to test the following hypotheses: 1. An algorithm can be developed which predicts cognitive performance in immersed exercising divers, based on the exhaled carbon dioxide (PETCO2) and the diver's inspired partial pressures of oxygen and nitrogen (PIO2 and PIN2). 2. PETCO2 using mass spectrometry is an accurate estimate of arterial carbon dioxide (PaCO2) at rest and during immersed exercise and can be used as a PaCO2 surrogate at levels exceeding 50 mmHg and depths up to 158 fsw (gas density 6.4 g/l, similar to 165 fsw density of 6.8 g/l).

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Conditions

Hypercapnia Exercise Nitrogen Narcosis Diving Immersion

Eligibility

Sex: MALEMin age: 18 YearsMax age: 50 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * healthy, * male, * age greater than 18, * age less than 50 Exclusion Criteria: * smoker, * asthma, * cardiac disease, * inability to pedal a bicycle ergometer, * inability to perform vigorous exercise

Outcomes

Primary Outcomes

Is cognitive ability different while resting versus compared to cognitive ability while diving, breathing different gas mixtures and while exercising?

Subjects will undergo computerized cognitive testing before, during and after a simulated dive in the Duke Hyperbaric Chamber. Different exercise conditions (rest or exercise) and different breathing gas mixtures (added carbon dioxide or not)will be assessed and compared to the pre-dive conditions.

Time frame: pre-dive to dive to post-dive (approximately 2 hours)

Secondary Outcomes

How does exhaled (end tidal) carbon dioxide compare with arterial carbon dioxide?

Exhaled (end tidal) carbon dioxide will be compared to arterial carbon dioxide at the various experimental conditions of the study (at the surface versus during the dive, during exercise versus during rest, breathing gas with added carbon dioxide versus breathing gas without added carbon dioxide)

Time frame: pre-dive to dive to post dive (approximately 2 hours)