Changes in heart-rate, blood-pressure, and duration of systole resulting from bicycling / by Wilbur P. Bowen.

  • Bowen, Wilbur Pardon, 1864-1928
Date:
[1904?]
Catalogue details

Licence: Public Domain Mark

Credit: Changes in heart-rate, blood-pressure, and duration of systole resulting from bicycling / by Wilbur P. Bowen. Source: Wellcome Collection.

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    rapidly shortening, I was inclined to consider the result apparent rather than real, and tried to account for the unexpected result in the following ways: 1. As an error of observation in reading the records. 2. Asa failure of the tambour to record the pulse-waves correctly, because of its having a vibration period of its own. 3. As a failure to record the pulse correctly because of changes of air-pressure within the tambour system, due to contraction of muscles of the neck. 4. Asa possible effect of changes in blood-pressure upon the times of opening and closing of the aortic valves, and consequent change in the apparent length of systole. After many careful tests of the apparatus, and after observing the same results in nearly one hundred experiments on about thirty different subjects, using tambours of different sizes, levers of various lengths, and membranes of different thickness, it has not been possible to find any reason to suspect the apparatus or the methods of reading the curves. With regard to the effect of changes in blood-pressure on the ap- parent length of systole, as indicated by the positions of the primary upstroke and the dicrotic notch, it is clear that increased pressure in the aorta would tend to delay the opening of the valve and hasten its closure, thus rendering our measure of the duration of systole from the pulse-curve too short;: similarly, a fall of pressure in the aorta, such as takes place when work stops, would hasten the opening of the valve and delay its closure, and so render the measure too long. In other words, at the time when we observe a lengthened systole, the change in blood-pressure, by its influence on the time of opening and closing of the semilunar valves, tends to make the systole appear shorter than it really is; and when the shortened systole is observed, the blood-pressure is acting to make it appear longer than it really is. The effect of these changes in blood-pressure is thus seen to minimize the real change in duration of systole rather than to account 1OGe i It should also be taken into account that determination of duration of systole during muscular work was not attempted by former writers, and therefore a change of systole and cycle in opposite directions is not a contradiction of former results, but an observation in a new field. Taking all into consideration, it seems reasonable to conclude that
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