Recruiting

Oxygen Toxicity

Sponsor:

Duke University

Code:

NCT05761756

Conditions

Oxygen Toxicity

Hypercapnia

Seizures

Eligibility Criteria

Sex: All

Age: 18 - 45

Healthy Volunteers: Accepted

Interventions

Sleep Deprivation

Caffeine

Methylphenidate

Carbon Dioxide

Study Details

Brief summary:

The goal of this clinical trial is to learn about the mechanisms of oxygen toxicity in scuba divers. The main questions it aims to answer are:

  • How does the training of respiratory muscles affect oxygen toxicity?
  • How do environmental factors, such as sleep deprivation, the ingestion of commonly utilized medications, and chronic exposure to carbon dioxide, impact the risk of oxygen toxicity?
  • How does immersion in water affect the development of oxygen toxicity?

Participants will be asked to do the following:

  • Undergo a basic screening exam composed of health history, vital signs, and some respiratory function tests
  • Train their respiratory muscles at regular intervals
  • Exercise on a cycle ergometer both in dry conditions and underwater/under pressure in the context of medication, sleep deprivation, or carbon dioxide exposure

Researchers will compare the performance of each subject before and after the possible interventions described above to see if there are changes in exercise performance, respiratory function, cerebral blood flow, and levels of gene expression.

Conditions

Oxygen Toxicity

Hypercapnia

Seizures

Study ID

NCT05761756

Start date

Nov 28, 2023

Status verified date

Oct, 2025

Completion date

Aug 31, 2026

Anticipated

Primary completion date

Aug 31, 2026

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 45

Healthy Volunteers: Accepted

Inclusion Criteria:

  • Equal numbers of male and female
  • Non-smokers
  • Aged 18-45 years
  • Males will be required to have VO2 peak > or equal to mL/kg min
  • and females > or equal to 30 mL/kg min

Exclusion Criteria:

  • Pregnancy
  • Cardiorespiratory disease, including hypertension
  • Neuromuscular disease
  • Anemia
  • History of hemoglobinopathy, including sick cell disease and trait

Study Design

Enrollment

62 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Prevention

Interventions and Outcome Measures

Arms

active comparator: Sleep Deprivation

Effect of sleep deprivation on HCVR and arterial PCO2 during submersed rest and exercise at 98 fsw. Ten subjects will be tested before and after 24 hours of sleep deprivation. The order of sleep deprivation vs. control will be randomized. Measurements at 98 fsw will be obtained at rest and during 10 minutes of moderate exercise in thermoneutral (29-30°C) water.

experimental: Caffeine

Effect of caffeine and methylphenidate on HCVR and arterial PCO2 during submersed rest and exercise at 98 fsw. Twenty subjects will be similarly sleep-deprived, tested as above and then re-tested tested following oral administration of administration of either oral caffeine (N=10) or methylphenidate (N=10). Pre-dive caffeine will be administered 500 mg orally \[59\]. Pre-dive methylphenidate will be administered as a single dose of 5 mg \[60\]. The order of drug administration vs. control will be randomized. Measurements at 98 fsw will be obtained at rest and during 10 minutes of moderate exercise in thermoneutral (29-30°C) water. fNIRS will be used to assess cerebral oxygenation and regional blood volume.

experimental: Methylphenidate

Effect of caffeine and methylphenidate on HCVR and arterial PCO2 during submersed rest and exercise at 98 fsw. Twenty subjects will be similarly sleep-deprived, tested as above and then re-tested tested following oral administration of administration of either oral caffeine (N=10) or methylphenidate (N=10). Pre-dive caffeine will be administered 500 mg orally \[59\]. Pre-dive methylphenidate will be administered as a single dose of 5 mg \[60\]. The order of drug administration vs. control will be randomized. Measurements at 98 fsw will be obtained at rest and during 10 minutes of moderate exercise in thermoneutral (29-30°C) water. fNIRS will be used to assess cerebral oxygenation and regional blood volume.

experimental: Carbon Dioxide Exposure

Effect of simulated chronic CO2 exposure on HCVR and arterial PCO2 during submersed rest and exercise at 98 fsw. Ten subjects will be studied before and after induction of metabolic alkalosis as described above with daily oral administration of sodium bicarbonate. Oral bicarbonate to simulate hypercapnia exposure will seek to increase serum bicarbonate to 30 mM/L via daily oral intake of 6 teaspoons of NaHCO3 for five days. Subsequently, blood will be drawn and intake adjusted as necessary \[61\]. The order of alkalization vs. control will be randomized. Measurements at 98 fsw will be obtained at rest and during 10 minutes of moderate exercise in thermoneutral (29-30°C) water.

Interventions

Sleep Deprivation

24 hours sleep deprivation

Caffeine

Oral administration of caffeine

Methylphenidate

Oral administration of methylphenidate

Carbon Dioxide

Oral administration of sodium bicarbonate to simulate carbon dioxide exposure

Primary outcome measure

  • Hypercapnic ventilatory response [ Time Frame: 3 months ]

Central Contacts and Locations

Central contacts

Derek B Covington, MD

919-613-8881derek.covington@duke.edu

Richard Moon, MD

919-613-8881Richard.moon@duke.edu

Locations

Duke University Health Sustem

Recruiting

Durham, North Carolina, United States, 27705

Contacts

Derek Covington, M.D.

919-613-8881derek.covington@duke.edu

More Information

Sponsor

Duke University

Last update posted

Oct 23, 2025

Last verified

Oct, 2025

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by Duke University on 2025-10-23.