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  • Title: Seadragon VI: a 7-day dry saturation dive at 31 ATA. IV. Circadian analysis of body temperature and renal functions.
    Author: Konda N, Shiraki K, Takeuchi H, Nakayama H, Hong SK.
    Journal: Undersea Biomed Res; 1987 Sep; 14(5):413-23. PubMed ID: 3672652.
    Abstract:
    Circadian rhythms of body temperature and daytime rhythms of urine flow and urinary excretion of electrolytes were investigated in 4 male subjects before, during, and after a 7-d stay in a dry heliox 31 ATA environment. The chamber temperature was maintained at about 28 degrees C during pre- and postdive 1 ATA periods and was raised to 31.5 degrees C at 31 ATA. The circadian rhythm of the rectal temperature, as analyzed by the cosinor fitting method, showed the same mesor (the mean level of fluctuation) and the amplitude at 31 and 1 ATA. However, a reversible phase shift was noted at 31 ATA in which the acrophase shifted to 1435 h at 31 ATA from 1540 h (predive) or 1610 h (postdive) at 1 ATA. This shift was attributed to an early rise of rectal temperature during night at 31 ATA. A similar phase shift was observed at 31 ATA for the skin temperature of the forehead, a region not covered by clothing or blanket. The daytime rhythms of urinary excretion of water, Na, Cl, urea, and total osmotic substances were similar, with the acrophase at 1300-1500 h at both 1 and 31 ATA. On the other hand, the daytime rhythm for urinary excretion of K, which was similar to the above at 1 ATA, disappeared at 31 ATA. The urinary excretion of endogenous creatinine remained constant during both daytime and nighttime at both 1 and 31 ATA. These results suggest that exposure to 31 ATA may alter the underlying pattern of circadian or daytime rhythms for thermoregulatory and certain renal functions.
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