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Biomedical subjects

K Burnett

Publications and source records attributed to K Burnett.

At least 73 records · Page 4Linked to original sources
PubMed1988

Assessment of cardiac size on portable chest films.

Using both anthropomorphic phantoms and human patients, the authors have shown that the effects on cardiothoracic (CT) ratio of changing from the posteroanterior (PA) to the anteroposterior (AP) projection are much greater than the effect of reducing the anode-to-film distance (AFD). This is because, in the AP projection, not only is the transverse diameter (TD) of the heart much farther from the film (and its image is therefore enlarged), but the TD of the chest is usually closer to the film and its image is reduced in size. These factors, operating in different directions, cause a major change in the CT ratio. The authors have shown that small hearts are magnified more than large hearts by changing from PA to AP, and that the position of the TD of the thorax (whether it is farther anterior or farther posterior) markedly affects what happens to the CT ratio when the AFD is changed. Because of this, it is impossible to predict accurately what effects a given AFD and projection will have on the CT ratio. However, using approximate correction factors (-12.5% of CT ratio for a 40 in AFD, AP film and -10% of CT ratio for a 72 in AFD, AP film) a clinically useful determination can be rapidly made as to whether the heart is enlarged or not.

Cardiomegaly↗
PubMed1986

Assessment of prescribed increases in physical activity: application of a new method for microprocessor analysis of heart rate.

A portable solid-state recorder-display system was used to measure and analyze heart rate during the waking hours of 3 consecutive days in free-living sedentary normal middle-aged men who were randomized to undergo 3 regimens of physical activity during a 12-week period: low-intensity exercise training at home (n = 21), high-intensity exercise training at home (n = 23) and customary activity (n = 20). This was done to determine whether the system could detect changes in heart rate and, indirectly, in physical activity within the 3 groups. In both training groups the percentage of total recorded time spent within the prescribed high or low heart rate range recorded at 6 or 12 weeks increased significantly (p less than 0.05), whereas control subjects showed no increase above baseline values. Peak oxygen consumption increased by 8% and 17% in men undergoing low- and high-intensity training, whereas in control subjects it did not change. This solid-state system reliably measures prescribed increases in heart rate and provides an indirect measure of physical activity in normal sedentary men undergoing exercise training at home.

Ambulatory Care↗