Hypercapnia: Cognitive Effects and Monitoring

Study Overview
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Brief Summary
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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).

Official Title
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Hypercapnia: Cognitive Effects and Monitoring

Conditions
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Hypercapnia, Exercise, Nitrogen Narcosis, Diving, Immersion

Intervention / Treatment
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* Other: NO exercise at depth
* Other: exercise at depth


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: dive to 122 feet, no exercise<br>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<br>* Subjects will NOT exercise while at depth<br>|
| Experimental: dive to 158 feet, no exercise<br>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<br>* Subjects will NOT exercise while at depth<br>|
| Experimental: dive to 122 feet, exercise<br>Subjects will undergo a simulated dive to a maximum depth of 122 feet of seawater with exercise at depth | Other: exercise at depth<br>* Subjects will exercise while at depth<br>|
| Experimental: dive to 158 feet, exercise<br>Subjects will undergo a simulated dive to a maximum depth of 154 feet of seawater with exercise at depth. | Other: exercise at depth<br>* Subjects will exercise while at depth<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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. | pre-dive to dive to post-dive (approximately 2 hours) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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) | pre-dive to dive to post dive (approximately 2 hours) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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diving, cognitive impairment, nitrogen narcosis, narcosis, end tidal carbon dioxide, arterial carbon dioxide, immersion