Effects of fasting and carbohydrate consumption on resting voluntary apneas in humans
Conniff, Mary Elizabeth
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A breath-hold can be defined as an apnea or a period of time during which respiration stops. Normally, it is very unlikely that voluntary breath-holds are held to a point where oxygen levels become low enough to result in unconsciousness. This is due to a strong urge to breathe that results in the termination of the apnea. The urge to breathe is mainly the result of increased CO 2 levels in the blood produced from metabolic processes. During lipid metabolism less carbon dioxide is produced compared to carbohydrate metabolism for a given energy output. It has recently been shown that a combination of 18 h of a carbohydrate free diet and prolonged exercise prior to breath-holding lowered Respiratory Exchange Ratio (RER) and PO 2 at maximal break-point. It this thesis it was hypothesized that fasting will result in decreased blood glucose levels and a lower RER. At the same time, breath-hold duration will be increased and end-tidal CO 2 and O 2 after the breath-hold will be decreased following fasting. It was also hypothesized that blood glucose, RER, SaO 2 %, and end-tidal gases will be increased following carbohydrate consumption while breath-hold duration will be decreased.