What Researchers Did
Researchers tested how well the body handles standing up after 6 hours of water immersion, comparing groups that breathed either regular air or oxygen at mild pressure (1.35 ATA), with or without being in the water.
What They Found
In this experimental study of 32 healthy men, three of the ten men who breathed air during water immersion became lightheaded (presyncope) during the post-immersion standing test, while none of the men who breathed hyperbaric oxygen, either alone or combined with immersion, had this problem. After air-immersion, heart rate rose 10% and systolic blood pressure fell 13% during the standing test. After hyperbaric oxygen combined with immersion, heart rate rose 17% and systolic blood pressure fell 8%. After hyperbaric oxygen alone with no immersion, heart rate and stroke volume did not change, while systolic and diastolic blood pressure rose 5% and 10% respectively.
Canadian Relevance
No direct Canadian connection identified.
Study Limitations
The study involved only 32 healthy men in small groups (10 to 12 per condition) tested after a single 6-hour exposure, so the results may not apply to women, patients with health conditions, or longer or repeated exposures.