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Reprint: Effect of Intermittent Exposure to 3% CO2 on Respiration, Acid-Base Balance, and Calcium-Phosphorus Metabolism., Availability: Pub. in Undersea Biomedical Research, Submarine Supplement, pS115-S134 1979.

The proportion of submariners wearing eyeglasses has increased considerably in the last generation, raising the question as to how much leakage occurs when emergency breathing masks are worn over eyeglasses. The amount of leakage into the Oxygen Breathing Apparatus (OBA) was measured when it was worn over five different types of eyeglass frames as well as with no frames by shaven and bearded men. If the frame was small enough to fit under the mask, there was relatively little leakage compared with the other two masks carried on submarines. All the frames except the Standard Navy issues S-10 frame (which would not fit under the mask) were rated as reasonably comfortable, although the spectacle insert specifically designed to be used with the OBA was not rated as highly as the other frames. Originator supplied keywords include: Atmospheric contaminants, and Gas masks.

One healthy male subject was exposed for six days, 15 hours daily, to a CO2 concentration rising from 0 - 3% CO2 at normal oxygen concentrations of 20 - 21% O2. Average data of physiological measurements made (A) prior ot and (B) at the end of the 15-hour exposure to CO2 concentration, rising linearly from 0 - 3% CO2 were pACO2(A): 40.7 mm Hg; pACO2(B): 42 mm Hg; pAO2(A): 100.7 mm Hg; PAO2(B): 114.8 mm Hg; VE(A): 6.28 L/m; VE(B): 12.09 L/m. pACO2 determined at the end of the none-hour air breathing rose from the third day on to reach, at the fifth day, a peak higher than the corresponding value following 15 hours of CO2 inhalation. During the sixth day of intermittent exposure to CO2, pAO2 on air returned to control values. This finding indicates that after three days the nine-hour period of air breathing was insufficient to eliminate the CO2 accumulated during the 15-hour period of CO2 breathing. Ventilatory response to 5% CO2 was increased during intermittent exposure to CO2 and the slope of the CO2 tolerance curve was also increased.

Pulmonary gas exchange and related renal regulation as indicated in urinary electrolyte exchange were measured during saturation-excursion dives to 800 and 1000 feet of sea water (FSW) for the purpose of determining beginning physiological limitations of underwater operations at these depths. Alveolar CO2 tension, oxygen consumption, and CO2 excretion did not change significantly from pre-dive control values during rest and exercise (100 watt) at 800 and 1000 FSW, which indicates that there is no respiratory limitation for moderate work load at the depth of 1000 FSW. Urinary electrolyte excretion showed a characteristic pattern during the saturation-excursion period, consisting in increased urine volume, large rise in bicarbonate excretion, and decrease in chloride excretion. Bends which did not respond to recompression and were found to be associated with large increases in bicarbonate excretion appear to be caused by excessive fluid shifts. It is suggested that in such cases liquid therapy should be instituted to compensate for the loss of liquid during the dive.