Seven normal, healthy, male volunteer subjects were exposed to four different environmental conditions at random on four separate occasions: breathing room air with an ambient temperature of 25(DEGREES)C (NN); breathing room air with an ambient temperature of 8(DEGREES)C (NC); breathing an hypoxic gas mixture (12% oxygen in nitrogen) with a neutral temperature (HN); and breathing an hypoxic gas mixture in the cold (HC). Measurements were taken pre-exposure and every 15 min during 90 min of resting exposure and 30 min of exercise of heart rate, blood pressure, core temperature, pulmonary ventilation, and oxygen uptake. Blood samples were taken by venipuncture pre-exposure, at 45 and 90 min of resting exposure, and 5 min post-exercise and subsequently analyzed for glucose, glycerol, and lactic acid concentration. Shivering was measured by electromyography during the two cold exposures. / Hypoxia led to significant increases in heart rate, systolic blood pressure, ventilation, respiratory quotient, blood lactate, and perceived exertion during exercise, while causing significant depression of core temperature and oxygen uptake. Exposure to cold significantly increased systolic and diastolic blood pressure, pulmonary ventilation, oxygen uptake, blood glucose, and blood glycerol, while resulting in significant decreases in heart rate, core temperature, and respiratory quotient. Shivering and diastolic pressure were significantly higher, and core temperature was significantly lower, in HC compared to NC. Heart rate, systolic pressure, ventilation, respiratory quotient, and blood lactate showed tendencies to be elevated in HC compared to NC, while oxygen uptake and blood glycerol tended to be depressed. These results suggest that (1) the work output and energy requirements of the myocardium may be greater in HC than in NC, since 'pressure work' is more energetically expensive than 'volume work', in which only stroke volume and cardiac output are augmented, and (2) hypoxia concomitant with cold exposure may result in an increased reliance on shivering for heat production. / Source: Dissertation Abstracts International, Volume: 48-03, Section: A, page: 0596. / Thesis (Ph.D.)--The Florida State University, 1987.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76075 |
| Contributors | ROBINSON, KEITH ALLEN., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 197 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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