Hyperbaric diuresis at a thermoneutral 31 ATA He-O2 environment

Area of Science:

• Physiology
• Hyperbaric Medicine
• Environmental Science

Background:

• Understanding body water exchange is crucial for safe diving.
• Previous studies suggested cold stress might influence water balance in hyperbaric conditions.

Purpose of the Study:

• To investigate the effects of a thermoneutral hyperbaric environment on body water exchange.
• To determine the cause of hyperbaric nocturia and its relation to environmental factors.

Main Methods:

• Four Japanese male divers were exposed to 31 ATA (He-O2) for 3 days in a thermoneutral environment.
• Rectal and mean skin temperatures were monitored hourly.
• Urine flow, fluid intake, body weight, and hematocrit were measured to assess water balance.

Main Results:

• Exposure to 31 ATA increased daily urine flow and decreased insensible water loss.
• Fluid intake reduced by 600 ml, resulting in negative fluid balance and decreased body weight.
• Hyperbaric nocturia was observed, identified as a water diuresis, not related to cold stress.

Conclusions:

• Hyperbaric diuresis at 31 ATA is primarily driven by increased overnight urine production.
• Hyperbaric nocturia in thermoneutral conditions is a water diuresis and not caused by cold stress.
• Divers can experience dehydration in hyperbaric environments due to reduced fluid intake and altered water excretion patterns.