Hypercapnia: Cognitive Effects and Monitoring

Sponsor

Duke University (Other)

Overall Status

Completed

CT.gov ID

NCT01782625

Collaborator

(none)

Enrollment

Location

Arms

Duration (Months)

1.6

Patients Per Site Per Month

Study Details

Study Description

Brief Summary

The investigators will simulate the conditions of a working, helmeted diver by using exercising, "head out" immersed subjects to test the following hypotheses:

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).
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).

Condition or Disease	Intervention/Treatment	Phase
Hypercapnia Exercise Nitrogen Narcosis Diving Immersion	Other: NO exercise at depth Other: exercise at depth	N/A

Study Design

Study Type:

Interventional

Actual Enrollment :

58 participants

Allocation:

Randomized

Intervention Model:

Parallel Assignment

Masking:

None (Open Label)

Primary Purpose:

Basic Science

Official Title:

Hypercapnia: Cognitive Effects and Monitoring

Study Start Date :

Jan 1, 2013

Actual Primary Completion Date :

Feb 1, 2016

Actual Study Completion Date :

Feb 1, 2016

Arms and Interventions

Arm	Intervention/Treatment
Experimental: dive to 122 feet, no exercise Subjects will undergo a simulated dive to a maximum depth of 122 feet of seawater with no exercise at depth	Other: NO exercise at depth Subjects will NOT exercise while at depth
Experimental: dive to 158 feet, no exercise Subjects will undergo a simulated dive to a maximum depth of 154 feet of seawater with no exercise at depth	Other: NO exercise at depth Subjects will NOT exercise while at depth
Experimental: dive to 122 feet, exercise Subjects will undergo a simulated dive to a maximum depth of 122 feet of seawater with exercise at depth	Other: exercise at depth Subjects will exercise while at depth
Experimental: dive to 158 feet, exercise Subjects will undergo a simulated dive to a maximum depth of 154 feet of seawater with exercise at depth.	Other: exercise at depth Subjects will exercise while at depth

Outcome Measures

Primary Outcome Measures

Is cognitive ability different while resting versus compared to cognitive ability while diving, breathing different gas mixtures and while exercising? [pre-dive to dive to post-dive (approximately 2 hours)]
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.

Secondary Outcome Measures

How does exhaled (end tidal) carbon dioxide compare with arterial carbon dioxide? [pre-dive to dive to post dive (approximately 2 hours)]
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)