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Biomedical subjects

E A Harris

Publications and source records attributed to E A Harris.

At least 91 records · Page 5Linked to original sources
PubMed1976

Gas exchange during exercise in healthy people. I. The physiological dead-space volume.

1. Physiological dead-space volume (V D) was measured in twenty-four healthy men and women aged from 20 to 71 years, at rest and at two rates of work on a treadmill, whilst breathing air and breathing oxygen. 2. The effect of correction of arterial carbon dioxide tension (Pa,CO2) to pulmonary capillary temperature on the resulting value for V D was investigated. We find that the effect is substantial and that a correction should be made. 3. Equations have been derived for the prediction of normal V D during exercise. The best prediction was given by a regression on height, age, carbon dioxide output, ventilation and respiratory frequency, with an upper 95% confidence limit of +81 ml.

Adult↗
PubMed1976

Gas exchange during exercise in healthy people II. Venous admixture.

1. Venous admixture/cardiac output ratio (Qva/Qt) has been measured in twenty-four healthy volunteer subjects of both sexes aged 20-71 years, at rest and during the steady state of treadmill exercise at two rates of work, and breathing air and breathing oxygen. 2. With oxygen breathing, Qva/Qt was considerably less during exercise than during the time subjects were taking either normal or deep breaths of oxygen at rest, and did not significantly increase with the intensity of exercise. It is postulated that the increase in ventilation during exercise opens most or all of those alveoli which, during oxygen breathing at rest, close because of critically low ventilation/perfusion (V/Q) ratios. 3. With air breathing, Qva/Qt fell from rest to exercise (especially in older subjects), presumably due to improved ventilation of alveoli at the lung bases. With an increase in work rate Qva/Qt increased in all age groups. This increase was not due to increase in the shunt fraction (Qs/Qt), nor to limitation of diffusing capacity; it arose from an increase in V/Q variance. 4. Equations have been derived for the prediction of normal Qva/Qt during exercise, with or without correction for the effects of increasing pulmonary capillary temperature. These effects do not materially influence the accuracy of prediction, but may be relevant to some of the interpretations. In particular, they provide a further indication that Qs/Qt probably cannot be measured by breathing oxygen at rest, even in deep breathing.

Adult↗
PubMed1976

Regional differences in lactate concentration in experimental myocardial infarction.

Lacate concentrations were measured in blood from (a) coronary veins within ischaemic myocardium and (b) veins nearer to the coronary vein, for periods of up to 2 1/2 hours after ligation of the left anterior descending artery in dogs. Concentrations at (a) were three to four times higher than at (b), while blood sampled simultaneously from two veins at (a) yielded similar concentrations of lactate. At 2 1/2 hours after ligation the veno-arterial difference of lactate concentration in blood from (a) was about one half of the difference at 15 minutes. Lactate concentration at (a) was approximately twice as great when the area of ischaemic myocardium drained by the vein was large (18 not equal to 1% of heart weight) than when it was small (6 not equal to 1% of heart weight). No close correlation was apparent between the height of epicardial ST-segment elevation and the level of lactate release. These experiments extend previous observations that changes in lactate concentration at a given site may reflect changes in venous dilution, rather than in the rate of production of lactate, and emphasize that caution is necessary in interpretation of changes in concentrations of metabolites in coronary sinus blood after acute myocardial infarction in man.

Animals↗
PubMed1976

Coronary perfusion and myocardial metabolism during open-heart surgery in man.

Myocardial oxygen consumption and extraction of lactate and free fatty acids (FFA) have been measured in six patients during cardiopulmonary bypass at two coronary flow rates differing by 25 per cent (109 and 148 ml. per minute). Significant differences were found between these flows and between natural and artificial coronary perfusion. This fact indicates the presence of anaerobic metabolism, especially at the lower coronary flow. These findings are discussed in relation to criteria for coronary flow and perfusion pressure during open-heart procedures.

Adult↗
PubMed1976

Measurement of cardiac output by thermodilution in infants and children after open-heart operations.

Five hundred twenty-five measurements of cardiac output were made in 26 infants and children after primary repair of congenital cardiac defects. The Edwards Model 9500 thermodilution output computer was used. Cold indicator was injected into the right atrium; in 405 measurements the signal was sensed in pulmonary artery (PA) and in 120 in left atrium. One hundred seven measurements of output by dye dilution (DD) were made in 9 of the infants. Reproducibility was only slightly less good for thermodilution (ID) with PA sensing than for DD but was considerably worse with left atrial sensing. Outputs measured by TD agreed well with those by DD (r = 0.9065). Precautions necessary for accurate measurements and the advantages of TD in infants are discussed.

Body Temperature↗
PubMed1975

A comparison of the actions of ICI66082 and propranolol on cardiac and peripheral beta-adrenoceptors.

The relative blocking potencies of ICI66082 and propranolol with respect to heart rate contractility, diastolic blood pressure and peripheral vascular conductance were compared in anaesthetized dogs. Peripheral blood flow was measured with an electromagnetic flow-probe around the descending aorta with retrograde cannulation of the inferior mesenteric artery for intra-arterial injections of isoprenaline. Cardiac and peripheral vascular effects of ICI66082 and propranolol were compared in terms of the shifts in the dose--response curves after i.v. and intra-arterial injections of isoprenaline. Propranolol was twice as potent as an equimolar dose of ICI66082 on cardiac beta-adrenoceptors. It was 70--130 times more potent in its action on the peripheral vascular receptors. Propranolol itself was 3 times more potent in blocking peripheral vascular receptors than cardiac beta-receptors. ICI66082 was 17--21 times more active in blocking the myocardial beta-adrenoceptors than those in the peripheral vessels. Electrophysiological studies showed that ICI66082 is devoid of membrane-depressant properties in concentrations up to 100 mg/l.

Action Potentials↗
PubMed1975

Spirometric standards from 387 healthy New Zealand children.

Vital capacity and forced expiratory volume in 1 s were measured in 387 healthy European and 16 non-European children aged from five to 11 years. These measurements were correlated with height, sitting height, arm span, weight, lean weight and age in various combinations. Suitable linear regression equations are presented from which these lung volumes may be predicted with confidence limits down to approximately +/- 400 ml and +/- 200 ml respectively.

Age Factors↗
PubMed1972

Multicentre, short-term therapeutic trial of disodium cromoglycate, with and without prednisone, in adults with asthma.

A total of 117 asthmatic patients were studied in a double-blind, cross-over trial with half-periods of three weeks in which disodium cromoglycate (D.S.C.G.) was compared with an inactive preparation. D.S.C.G. improved spirometric measurements, at a very high level of statistical significance, more than did placebo. The mean advantage of D.S.C.G. was less than 10% after three weeks. Symptomatic improvement by D.S.C.G. was small though significant; it was not correlated with spirometric improvement. A history of chronic cough was the only clinical characteristic associated with a better-than-average spirometric response to D.S.C.G.

Adult↗