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Biomedical subjects

C E Tucker

Publications and source records attributed to C E Tucker.

4 recordsLinked to original sources
PubMed1990

The coronary stress of skiing at high altitude.

Skiing, which may involve strenuous exercise in the cold at high altitude, could place considerable stress on the coronary circulation. To explore this possibility, we obtained by telemetry electrocardiograms on 149 men during recreational skiing at altitudes above 3100 m (10 150 ft). Tachycardia was impressive; heart rate exceeded 80% of predicted maximum in two thirds of the subjects. Five men developed abnormal ST-segment depression during or immediately after exercise. All five were older than 40 years, so in this age group the incidence of ST abnormalities was 5.6%. This is not greater than the incidence among asymptomatic men during submaximal exercise at low altitude. The high level of physical fitness of men who ski may have offset the added stress of cold and hypoxia. Hence, for physically fit older men, mountain skiing does not appear to pose a greater coronary stress than does comparable exercise at low altitude among men of only average physical fitness without known heart disease.

Adult↗
PubMed1979

Cardiac function in goats exposed to carbon monoxide.

To investigate the possibility that prolonged carbon monoxide (CO) exposure would depress myocardial function, six chronically instrumented, unsedated goats were exposed to 160--200 ppm CO for 2 wk, resulting in a mean carboxyhemoglobin saturation of 20%. Cardiac index and stroke volume remained unchanged during and after exposure. Hematocrit and hemoglobin concentration started increasing on the 10th day of exposure, this increase reached statistical significance (P less than 0.05) on the 6th postexposure day. Contractility (Vmax) of the left ventricular myocardium and heart rate were unchanged during exposure to CO, but both were significantly (P less than 0.05) decreased at some time during the 1st wk after removal from CO. If there was a decrease in intrinsic myocardial function during CO exposure, it may have been masked by increased sympathetic activity. The mechanism(s) that might produce the decrease in heart rate and contractility after removal from CO are not obvious. Possible explanations are discussed.

Animals↗
PubMed1976

Depressed myocardial function in the goat at high altitude.

To determine if depressed myocardial function contributes to the reported decrease in cardiac performance at high altitude, six chronically instrumented, unsedated goats were studied before, during, and after 2-wk exposure to hypobaric hypoxia (PaO2 44 mmHg). Undistorted ventricular pressure wave form was obtained from a miniature transducer implanted in the left ventricular cavity. The relationship between (dP/dt)/28P and P was extrapolated to obtain Vmax as an index of myocardial function. With beta sympathetic blockade (practolol) and pacing to reproduce heart rates, Vmax was uniformly and significantly depressed (P less than 0.01) during chronic hypoxia, and returned to control values following descent to low altitude. Likewise, stroke volume following saline infusion was decreased at high altitude and returned to control values following descent. Acute relief of hypoxia at high altitude by administration of 100% oxygen by mask did not reverse the depressed Vmax. These findings indicate that chronic hypobaric hypoxia produces a depression of myocardial function which is reversible by chronic but not acute relief of hypoxia.

Adaptation, Physiological↗