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| Title: | Alveolar gas composition before and after maximal breath-holds in competitive divers. |
| Authors: | Lindholm, P
Lundgren, CEG |
| Keywords: | DIVING
RESPIRATORY
ventilation
alveolar gas
hypercapnia
carbon dioxide
breath hold
breath-hold
hyperventilate
Static Apnea
human |
| Issue Date: | 2006 |
| Publisher: | Undersea and Hyperbaric Medical Society, Inc. |
| Citation: | Undersea Hyperb Med. 2006 Nov-Dec;33(6):463-7. |
| Abstract: | The urge to breathe, as stimulated by hypercapnia, is generally considered to cause a breath-hold diver to end the breath-hold, and pre-breath hold hyperventilation has been suggested to cause hypoxic loss of consciousness (LOC) due to the reduced urge to breathe. Competitors hyperventilate before "Static Apnea", yet only 10% surface with symptoms of hypoxia such as loss of motor control (LMC) or LOC. We hypothesized that the extensive hyperventilation would prevent hypercapnia even during prolonged breath-holding and we also recorded breaking-point end-tidal PO2 in humans. Nine breath-hold divers performed breath-holds of maximal duration according to their chosen "Static Apnea" procedure. They floated face down in a swimming pool (28 degrees C). The only non-standard procedure was that they exhaled into a sampling tube for end-expiratory air, before starting the breath-hold and before resuming breathing. Breath-hold duration was 284 +/- 25 (SD) seconds. End-tidal PCO2 was 18.9 +/- 2.0 mmHg before apnea and 38.3 +/- 4.7 mmHg at apnea termination. End-tidal PO2 was 131.7 +/- 2.7 mmHg before apnea and 26.9 +/- 7.5 mmHg at apnea termination. Two of the subjects showed LMC after exhaling into the sampling tube; their end-tidal PAO2 values were 19.6 and 21.0 mmHg, respectively. End-tidal CO2 was normocapnic or hypocapnic at the termination of breath-holds. These data suggest that the athletes rely primarily on the hypoxic stimuli, probably in interaction with CO2 stimuli to determine when to end breath-holds. The severity of hypoxia close to LOC was similar to that reported for acute hypobaric hypoxia in humans. |
| Description: | Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc. |
| URI: | http://archive.rubicon-foundation.org/5053 |
| Appears in Collections: | Undersea and Hyperbaric Medicine Journal
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| 17274316.pdf | | 238Kb | Adobe PDF | View/Open |
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