Year: 1994
Type: dissertation
Abstract: Previous findings of a narcosis-induced reduction in heat production during cold exposure have been attributed to a reduced shivering response, as reflected in oxygen uptake (Mekjavic and Sundberg, 1992) however, the possibility of reduced oxygen utilization (902) by the muscles could not be excluded.Accordingly, the present study examined whether narcosis affects 3 0 2 during incremental load exercise to exhaustion (MAX) and submaximal steady state exercise (SUBMAX).Nine male subjects participated in both the MAX and SUBMAX trials on two separate occasions.On one occasion they inspired room air (AIR) while on the other they inspired a normoxic mixture containing 30% N 2 0 (N20).In the MAX trials, work rate was increased by 30 W.min-l until the cadence of 60 rpm could no longer be maintained.In the SUBMAX trials, subjects exercised for 20 min at 50% of maximal workrate (Wmax) as determined in the MAX-AIR trial.At minute intervals, measurements were made of esophageal temperature (Tes), sweating rate (Esw), forehead cutaneous blood perfusion (SkBP), heat flux (G), skin temperature (Tsk), heart rate (HR), ventilation (\iI) and 902.In addition, venous blood was analyzcd for lactate in the SUBMAX trials.Though subjects attaincd the same Wmax in the MAX-AIR and N 2 0 trials, (f SE) was significantly higher during N 2 0 (58.9 + 3.1 ml.kg-l.min-1)compared to the AIR condition (55.0 f 2.4 rnl.kg-1.min-1).However, the 902relative work rate relation was similar during both MAX-AIR and MAX-N20 at submaximal work rates.There was no statistically significant difference in 9 0 2 and plasma lactate concentration between the AIR and N 2 0 conditions of the SUBMAX trials.Though there was no difference in carbon dioxide production ( 9 ~0 ~) between the MAX trials, the respiratory exchange ratio (RER) was significantly lower during N 2 0 (1.15 + 0.02 compared to 1.25 + 0.03).There were no significant differences in the responses of Tes, Esw, SkBP, b, Tsk, HR and 91 between the AIR and N 2 0 trials of the MAX and SUBMAX tests.Thesc results suggest that narcosis, induced by 30% nitrous oxide, may increase oxygen extraction by the cells when muscles are iii working maximally, resulting in improved oxygen utilization without affecting the thermal balance or exercise thermoregulation mechanisms of the body.Furthermore, the narcosis-induced reduction in Go2 observed during cold water immersion can be interpreted as a reduction in the shivering response rather than decreased oxygen utilization by the muscles. Table of Contents....
Source: Summit (Simon Fraser University)
Author: Rita Alexandra Ciammaichella
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W30486736