Arterial oxygen desaturation kinetics during apnea
Purpose: To quantify the rate of arterial oxygen desaturation during apnea in freedivers. Methods: Ten freedivers and ten controls undertook five maximal face immersion apneas in 10 degrees Celsius water separated by 2 min of recovery. Electrocardiogram (ECG), blood pressure, and pulse oximetry were recorded continuously. Peripheral blood flow was measured by calf plethysmography every 30 s, and venous blood samples were collected at rest and after apneas 1, 3, and 5. The blood was analyzed for hematocrit (Hct), lactate, and hemoglobin (Hb) concentration. The arterial oxygen saturation (SaO2) data were curve fitted with both a sigmoid and two-slope continuous function. Results: Apnea duration increased with successive attempts, with freedivers achieving significantly longer maximal apneas (trained 246 44 s, untrained 129 39 s, P 0.001). Compared with controls, freedivers displayed a significant change from baseline in heart rate (trained 27.2 9.5 bpm, untrained 19.7 9.3 bpm, P 0.001) and mean arterial pressure (MAP) (trained 48 20.7 mm Hg, untrained 37 10.0 mm Hg, P 0.002), but no difference existed in peripheral blood flow, Hct, lactate, or Hb. The maximal slope of the SaO2 sigmoid curve was not significantly different between the groups (trained 0.16 0.05% s1, untrained 0.15 0.06% s1, P 0.26), but the SaO2/t obtained from the two-slope continuous model indicated that 85% of the variance in the freedivers SaO2/t could be explained by the apnea-induced bradycardia, preapnea vital capacity, and Hb concentration. Conclusions: The sigmoidal function provided no quantifiable difference in the rate of oxygen desaturation. The two-slope continuous method, however, indicated that freedivers who had larger oxygen stores and produced the largest bradycardia were able to slow the SaO2/t to two to three times that of the least marked response.
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|Item Type:||Journal Article|
|Additional Information:||Self-archiving of the author-version is not yet supported by this publisher. For more information, please refer to the journal's website (see hypertext link) or contact the author. firstname.lastname@example.org|
|Keywords:||Diving response, breath hold, arterial oxygen saturation, sigmoid logistic function|
|Subjects:||Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > MEDICAL PHYSIOLOGY (111600) > Systems Physiology (111603)
Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > HUMAN MOVEMENT AND SPORTS SCIENCE (110600) > Exercise Physiology (110602)
|Divisions:||Current > Research Centres > Centre for Health Research
Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 2005 Lippincott Williams & Wilkins|
|Deposited On:||21 Jun 2007|
|Last Modified:||29 Feb 2012 13:15|
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