Hypercapnia: Cognitive Effects and Monitoring

Not Applicable

Completed

• Conditions: Hypercapnia; Nitrogen Narcosis; Exercise; Diving; Immersion
• Interventions: Other: exercise at depth; Other: NO exercise at depth

• Registration Number: NCT01782625
• Lead Sponsor: Duke University

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:

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).

Detailed Description

Not available

Study Timeline

• Study Start: 2013-01
• Study First Submitted: 2013-01-31
• Study First Submitted QC: 2013-02-01
• Study First Posted: 2013-02-04
• Primary Completion: 2016-02
• Study Completion: 2016-02
• Status Verified: 2016-05
• Last Update Submitted: 2016-05-24
• Last Update Posted: 2016-05-25

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Male
• Target Recruitment: 58

Inclusion Criteria

• healthy,
• male,
• age greater than 18,
• age less than 50

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Exclusion Criteria

• smoker,
• asthma,
• cardiac disease,
• inability to pedal a bicycle ergometer,
• inability to perform vigorous exercise

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
dive to 122 feet, exercise	exercise at depth	Subjects will undergo a simulated dive to a maximum depth of 122 feet of seawater with exercise at depth
dive to 158 feet, exercise	exercise at depth	Subjects will undergo a simulated dive to a maximum depth of 154 feet of seawater with exercise at depth.
dive to 122 feet, no exercise	NO exercise at depth	Subjects will undergo a simulated dive to a maximum depth of 122 feet of seawater with no exercise at depth
dive to 158 feet, no exercise	NO exercise at depth	Subjects will undergo a simulated dive to a maximum depth of 154 feet of seawater with no exercise at depth

Primary Outcome Measures

Name	Time	Method
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

Name	Time	Method
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)

Trial Locations

Locations (1)

Duke Center for Hyperbaric Medicine and Environmental Physiology; 🇺🇸 Durham, North Carolina, United States