Renal responses during a dry saturation dive to 450 msw

Area of Science:

• Physiology
• Hyperbaric Medicine
• Environmental Science

Background:

• Previous saturation dives using helium-oxygen (He-O2) mixtures indicated potential fluid and electrolyte imbalances.
• Understanding physiological responses to extreme pressure is crucial for diver safety and performance.

Purpose of the Study:

• To investigate the physiological effects of a 37-day saturation dive to 450 msw (46 bar) using trimix on fluid and electrolyte balance.
• To confirm or refute observations of diuresis and natriuresis from prior He-O2 saturation dives.

Main Methods:

• Four subjects were exposed to 450 msw for 37 days in a hyperbaric chamber.
• Urine samples were collected multiple times daily for analysis of Na+, K+, volume, osmolality, and creatinine.
• Fluid, Na+, and K+ intake were monitored daily; urine antidiuretic hormone (ADH) and aldosterone were also analyzed.

Main Results:

• A significant diuresis and natriuresis occurred during compression and persisted throughout the hyperbaric exposure, despite decreased fluid intake.
• No significant change in overall fluid intake was observed, but daily Na+ and K+ excretion increased, particularly nocturnally.
• Urine ADH decreased upon compression, correlating with reduced urine osmolality, while urinary aldosterone showed no significant change.

Conclusions:

• The study confirmed a sustained diuresis and natriuresis during prolonged trimix saturation diving at 450 msw.
• Physiological responses include decreased urine ADH and osmolality, with altered electrolyte excretion patterns.
• Aldosterone levels did not adapt to the increased Na+ and K+ excretion, suggesting complex regulatory mechanisms under hyperbaric conditions.