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Biomedical subjects

D A Cunningham

Publications and source records attributed to D A Cunningham.

At least 145 records · Page 8Linked to original sources
PubMed1984

Aspirin inhibition of platelet deposition at angioplasty sites: demonstration by platelet scintigraphy.

In-111 platelet scintigraphy was used to evaluate the effects of prior aspirin administration on the accumulation of In-111-labeled autologous platelets at sites of arterial injury resulting from iliac, femoral, or popliteal transluminal angioplasty in a nonrandomized study of 17 men. The degree of platelet localization at angioplasty sites was significantly less in nine men who had received aspirin in varying doses within the 4 days before angioplasty than in eight men who had not received aspirin for at least two weeks. Our results suggest that aspirin treatment before angioplasty limits the early platelet deposition at the angioplasty site in men.

Adult↗
PubMed1984

Development of cardiorespiratory function in circumpubertal boys: a longitudinal study.

To investigate cardiorespiratory function during circumpubertal growth, 62 boys (aged 9-10 yr) were studied annually for 6 yr. Measurements of O2 uptake (VO2), cardiac output, and arteriovenous O2 difference were made during a submaximal bicycle test. Values were interpolated to a heart rate of 155 beats X min-1 (VO2 at a heart rate of 155) for comparisons across ages 10.8-14.8 yr. To account for growth differences among the boys, data were also aligned at yearly intervals relative to their individual age of peak height velocity (PHV; maturative age). The group was further divided into early, mid, and late maturers based on their year of PHV. VO2 and stroke volume (SV) of late maturers were larger at each maturative age. SV mirrored the increase in VO2 at all stages of development except during the period of most rapid growth. Arteriovenous O2 difference showed an increase in the year of peak growth with little change during any of the other maturative age intervals. Multiple regression analysis indicated that VO2 was determined primarily by the size of SV throughout this age range.

Child↗
PubMed1984

Regression analysis in physiological research: some comments on the problem of repeated measurements.

The statistical implications of repeated-measures linear regression, in which each subject contributes several pairs of measurements to the analysis, are discussed in the context of physiological research. The major point of the paper is that standard least-squares procedures cannot be applied without modification to regression problems with repeated measures. An example is given.

Adult↗
PubMed1984

Physical activity as a moderator of life events and somatic complaints: a longitudinal study.

During the past 15 years a very large number of studies have shown that life events are a significant stressor with attendant physiological and psychological outcomes. Much of this research was summarized by Dohrenwend and Dohrenwend (1974). There is also considerable literature suggesting that physical activity may be an effective coping mechanism which can buffer the relationship between an environmental stressor and such psychological and physiological outcomes. This paper reports on the relationship of life change events and somatic complaints and the moderating effects of physical activity. The study was longitudinal involving 278 managers from 12 different corporations. All participants were men. Data have been collected at entry, two years later, and four years later. This provides two test periods in which the data are analysed. Analyses are by way of multiple regression and in both time periods the change data support the hypothesis that somatic complaints are significantly related to both life events and physical activity. The results also show that physical activity has a significant buffering effect on the relationship between life events and somatic complaints. These findings lend strong support to the hypothesis that physical activity can be a significant moderator of the effects of environmental stress.

Administrative Personnel↗
PubMed1983

Characteristics that predicted recurrence of infarction within 3 years in the Ontario Exercise-Heart Collaborative Study.

Data on 13 baseline characteristics of 618 patients who had previously had a myocardial infarction and who had entered the Ontario Exercise-Heart Collaborative Study were analysed for their ability to predict recurrence of infarction within 3 years. These characteristics were age, serum levels of cholesterol and triglycerides, systolic and diastolic blood pressure, number of hours of competitive sports per week, number of hours of jogging per week, angina, type of occupation, smoking, cough and phlegm production, personality type and the number of previous infarctions. The characteristics showing independent statistical significance (p less than 0.05) were smoking and blue-collar occupation, with estimated adjusted relative odds of 2.3 and 2.1 respectively.

Adult↗
PubMed1983

Predictors of dropout from cardiac exercise rehabilitation. Ontario Exercise-Heart Collaborative Study.

The Ontario Exercise-Heart Collaborative Study was a multicenter randomized clinical trial of high intensity exercise for the prevention of recurrent myocardial infarction in 733 men. Of the 678 subjects who could have participated for at least 3 years, 315 (46.5%) dropped out. Stepwise multiple linear logistic regression analysis was carried out to examine the relation between subject characteristics and the probability of dropping out during the study. Analysis was performed on the entry group as a whole by considering those subjects who had reinfarction while complying with the program and also by excluding all subjects with reinfarctions. The consistent and statistically significant predictors of dropout in both analyses were smoking and a blue collar occupation. Angina was significantly associated with dropout only when reinfarctions were excluded. It may be important to consider these factors when investigating the potential for compliance-improving strategies in reducing dropout from exercise rehabilitation programs.

Adult↗
PubMed1983

Energy cost of treadmill and floor walking at self-selected paces.

Oxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19-29 years (n = 20) and 55-66 years (n = 22), walk at four self-selected paces, from "rather slowly" to "as fast as possible". A two-variable quadratic model relating VO2 (ml X kg-1 X min-1) to velocity (m X s-1) was adopted for prediction purposes. However, age and fatness significantly (P less than 0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m X s-1, the energy cost for the treadmill (age 55-66 years) was 10.58 ml X kg-1 X min-1 and for the floor, 11.04 ml X kg-1 X min-1 (P less than 0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations.

Adult↗
PubMed1983

The use of multivariate analysis of variance in physiological research: the two-group case.

The advantages of performing simultaneous inferences on the means of several response variables using multivariate analysis of variance are discussed. They include control over the problem of declaring false significant differences and the ability to investigate the effects of treatment on a given response variable after eliminating variations due to other response variables. Computational equivalencies with multiple linear regression in the two-group case are also discussed.

Analysis of Variance↗
PubMed1982

Angiography in gastrointestinal bleeding.

160 selective visceral angiograms were performed in 145 patients with gastrointestinal bleeding. In 52 studies done as emergency procedures (group A) 87% were positive, and in 108 elective procedures (group B) 74% were positive. The commonest lesion demonstrated in group B was angiodysplasia (43 patients) and most of these cases had previously undergone various investigations which had proved to be negative. Angiodysplasia is clearly an important cause of obscure gastrointestinal bleeding that may go unrecognised for many years. In addition to its diagnostic value angiography also proved extremely successful as a therapeutic measure in appropriate cases. Embolisation was performed in 36% of group A patients with positive angiograms, and in 10% of corresponding group B patients.

Acute Disease↗
PubMed1982

The consistency of cardiac output measurement (CO2 rebreathe) in children during exercise.

Exercise cardiac output (Q) was determined using the CO2 rebreathing equilibrium method. Five repeat tests in 12 boys and two tests over a 4 month interval in 47 boys were performed. Regression equations to predict Q from VO2 were in close agreement with dye dilution studies in boys (Eriksson and Koch 1973). Group mean data were reproducible from trial to trial. The day-to-day variability of Q, with a coefficient of variation of 7-8%, was found to be higher than when the CO2 method has been applied in adults. This greater variability was related, in part, to a larger biological variation in children as depicted in such relatively simple measures as submaximal exercise heart rate. The larger variability was also related to inaccuracies in the methods of PaCO2 estimation in children. Estimation from end-tidal CO2 concentrations requires further research to establish a correction for the alveolar-arterial gradient during exercise in children. Estimation of the child's dead space in exercise, with subsequent derivation of PaCO2 from the Bohr equation, also could be improved. Nevertheless, Q estimates in children exercising above VO2 1.01 X min-1 showed a day-to-day and long term stability acceptable for use in research and clinical studies.

Adolescent↗
PubMed1982

Determinants of self-selected walking pace across ages 19 to 66.

To describe the association between self-selected speeds of walking, and age, maximal aerobic power, and body size, 84 men aged 19 to 66 years were asked to walk at four self-selected paces, from rather slowly to as fast as possible. Speed of walking was measured over a 240-m indoor course. Maximal oxygen uptake was determined on a treadmill. The speed of walking was significantly slower in the oldest (55 to 66 years) compared with the youngest group (19 to 29 years) at the normal fast, and as fast as possible speeds. However, when age, weight, height, and fatness were held constant in a multiple regression model, VO2 max was significantly related to speed of walking at the three fastest walking paces. Age was not significantly related to speed of walking at any pace. Thus, this study indicated that the speed of self-selected walking paces was associated with maximal aerobic power independent of age.

Adult↗
PubMed1982

Effects of chronic exercise on cardiac output and its determinants.

A protocol which combines the noninvasive measurement of cardiac output (Q), systolic time intervals (STIs), and blood pressure was used to evaluate the effects of jogging on cardiac function. Studies were conducted during levels of steady-state cycle ergometer exercise which represented approximately 35, 55, and 75% of aerobic capacity. Subjects were 15 healthy men (mean age = 37.2 years) and 13 healthy controls. Predicted aerobic capacity (pred VO2max) increased 15 and 17% in the training group after 3 and 6 months of training; the control group displayed a small detraining effect. Changes in the training group versus control group included significant increases in exercise Q, stroke volume (SV), mean systolic ejection rate (MSER), and systolic blood pressure (SBP). Changes in STIs were small and usually nonsignificant. The findings, considered in relation to echocardiographic measurements from the same subjects (L. A. Wolfe, D. A. Cunningham, P. A. Rechnitzer, and P. M. Nichol. 1979 J. Appl. Physiol. 47: 207-212.), suggested that changes in cardiac output were due to an increased preload, rather than a change in exercise heart rate, reduced afterload, enhanced contractile state, or myocardial enlargement.

Adult↗
PubMed1981

201Thallium stress myocardial imaging: an evaluation of fifty-eight asymptomatic males.

The possible value of myocardial imaging with 201thallium as a screening procedure for the detection of latent disease has not been previously shown. Fifty-eight asymptomatic men underwent exercise 201thallium imaging together with a risk score profile based on the Framingham criteria for predicting future coronary events. Six subjects (10%) developed perfusion defects compatible with myocardial ischemia. The risk score for the population with an abnormal test was 7.7 +/- 2.9%, compared to 2.0 +/- 2.2% (p less than 0.001) for those men with normal tests. Three of the subjects with abnormal scans underwent selective coronary arteriograms; all three had normal coronary arteries. During a 30-month follow-up, all individuals remained physically active and free of cardiac symptoms. Exercise myocardial imaging is not a cost-effective means of detecting coronary artery disease in an asymptomatic population and should not be used as a screening procedure.

Adult↗
PubMed1981

The effect of different treadmill speeds on the variability of VO2 max in children.

Eight boys aged 10-12 years performed three tests on each of three treadmill protocols. Each test was a continuous, progressively graded performance to exhaustion, but protocols differed in speed--(walk: 90 m . min-1, jog: 110 m . min-1, run: 130 m . min-1). The walk protocol was found inappropriate for VO2 max determination in children. Compared to the faster speeds, the walk test elicited a lower VO2 at exhaustion, and had lower reliability (0.56) and a high coefficient of variation (8%). For the Vo2 at exhaustion on the jog and run protocols the coefficient of variation was 3-5% and the reliability coefficient averaged 0.90, comparable to values seen for repeated trials in adults. The usually accepted VO2 max criterion of a plateau of VO2 with increasing work levels was inappropriate for use with children. Attempts to derive plateau criteria suitable for use with children proved unsuccessful. Plateau criteria may be difficult to achieve with children in light of their apparently weaker glycolytic energy capacity. Nevertheless, the highest VO2 measured at jog or run speeds has a consistency similar to that found for Vo2 max measurement in adults.

Child↗
PubMed1981

Left ventricular function in marathon runners: echocardiographic assessment.

Cardiac alterations induced by chronic isotonic exercise were assessed echocardiographically in 8 active male marathon runners aged 29 +/- 7 yr (mean +/- SD) compared with 10 sedentary controls aged 27 +/- 5 yr. The runners had a significantly higher aerobic capacity than the controls (72.8 +/- 6 vs. 41.4 +/- 6 ml . kg-1 . min-1; P less than 0.001). Compared with the controls, the runners had a significantly lower heart rate at rest (49 +/- 3 vs. 73 +/- 9 beats/min; P less than 0.01) and during submaximal supine exercise at a similar absolute work load (115 +/- 11 vs. 124 +/- 12 beats/min; P less than 0.01). Similarly, the runners had a lower pressure-rate product both at rest (5.52 +/- 1.0 x 10(3) vs. 9.43 +/- 1.4 x 10(-3)) and during submaximal exercise (19.7 +/- 3.2 x 10(3) vs. 25.0 +/- 4.2 x 10(3); P less than 0.01). The left ventricular peak velocity of circumferential fiber shortening of the runners relative to that of the controls was significantly reduced both at rest (1.40 +/- 0.08 vs. 1.64 +/- 0.08 circ/s) and during submaximal supine exercise at a similar absolute work load (2.36 +/- 0.15 vs. 2.71 +/- 0.10 circ/s). However, this reduction in V cf was found to be directly related to the lower pressure-rate product of the runners and therefore did not reflect a decreased intrinsic myocardial contractility in the runners relative to the controls.

Adult↗