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Reduced Exercise Endurance after Repeated Long‐Duration Oxygen Dives — Do Ventilatory Parameters Hint at a Cause?
Author(s) -
Shykoff Barbara,
Bergeron Elizabeth,
Florian John
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.678.3
Subject(s) - respiratory quotient , ventilation (architecture) , partial pressure , zoology , anesthesia , medicine , oxygen , chemistry , meteorology , biology , physics , organic chemistry
Running endurance decreases after repeated long‐duration dives with oxygen partial pressure 1.3 atm. Physiological clues for the mechanism were sought from non‐invasive ventilatory and metabolic measurements during endurance exercise. Three groups of nine male Navy divers completed five days of 6‐hour dives breathing air or O 2 in 15 feet of water or O 2 at equivalent pressure dry while resting in a hyperbaric chamber. Several days before the first (Pre) and one day after the final dive (Post), they ran to their voluntary endurance limits on a treadmill at 85% of VO 2 max . Breath‐by‐breath data (Cosmed K4b2) were compared Pre – Post using one‐minute averages at the run time matching the last minute of the shorter of the two runs. Endurance times decreased with O 2 (wet:–29%, p<0.01; dry: –41%, p< 0.01), but did not change with air (–16%). Relative to Pre, Post for O 2 dives had higher minute ventilation (V’ E ) (wet: +12%, p < 0.01; dry: +25%, p <0.001) and lower end tidal CO 2 partial pressure (P ET CO 2 ) (wet:–5%, p<0.05; dry: –13%, p=0.01), and changes were more pronounced after dry than wet exposures. Wet but not dry O 2 increased respiratory quotient (R) Post relative to Pre (+7%, p < 0.03). Air dives caused no significant changes (V’ E : +1%; P ET CO 2 : –2%; R: –4%). Oxygen breathing but not immersion during five days of 6‐hour dives caused post‐dive metabolic changes during heavy endurance exercise. The increase in V’ E and decrease in P ET CO 2 at the same external workload suggests increased lactate production after repeated mildly‐hyperoxic exposures. Funding: ONR, and NAVSEA Deep Submergence Biomedical Program