On the influence of the position of the body on the position of the heart and on intracardiac pressure / by C.J. Bond.

  • Charles John Bond
Date:
[1885]
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Licence: Public Domain Mark

Credit: On the influence of the position of the body on the position of the heart and on intracardiac pressure / by C.J. Bond. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    [4] any alterations in blood-pressure produced by the anaesthetic. It occurs, too, after the inferior vena cava has been ligatured, and is not therefore due wholly to reflux of venous blood. It occurs also in the dead human heart, as I have found by means of a like instrument, passed not only into the right auricle, but also into the left auricle. It seems, therefore, certain that it is due to the mechanical effect of gravity acting on the heart, which falls back, compressing its base in the way described above. This fact, namely, that the intra-auricular pressure, and conse- quently the circulation, is affected mechanically by alterations in bodily position and respiration, has, I think, important bearings. First, physiologically. The heart, slung as it is from the great vessels above, and in man resting on the diaphragm below, has, it must be remembered, no power to fill itself, for the pressure in the great veins is slight, or often a minus pressure. This filling is due, of course, chiefly to the aspiratory influence of the thoracic movements of inspi- ration, and partly to the elastic tension of the lungs acting on the thin-walled auricles, while the above facts would suggest that it is also partly due to the fall of the heart, since it follows the descent of the diaphragm in inspiration, thus allowing its base to fill by the mechanical aspiratory influence of its own weight. The alterations in the arterial circulation known to exist in the standing or lying pos- tures may be partly produced by cardiac gravity. Secondly, pathologically. This mechanical theory seems to me to explain the peculiar position of cardiac dyspnoea. The patient who suffers from backward venous pressure—from any disease, in fact, cardiac or pulmonary, which impedes the filling of the auricles— naturally sits up in bed, turns on his left side, or bends a little for- ward, not only because respiration is thus more easy, but also because the heart in this position can fill better, owing to diminished intra- auricular pressure. In fact, the early stage of many such diseases is impeded cardiac diastole, which is thus mechanically overcome. Also it has been found that, in the feebly-acting heart of partial chloroform- syncope, the best treatment is to roll the patient gently on to his left side, in a semi-prone position. Inversion (Nelaton) acts at first beneficially, of course, by increasing the blood-pressure in the anaemic central nervous system ; but, if long continued, its heart-impeding effects soon become manifest. Further, the peculiar cardiac embarrassment produced by upward pressure of the diaphragm, from whatever cause is thus explained by its acting, not only on pulmonary respiration, but also directly on the position of the heart. From the anatomical relations of the base of the heart, the right pulmonary vein passing behind the right auricle, being connected to it by pericardial folds, to reach the left auricle, any overdistension of the right side would excite unequal pressure on the pulmonary veins, and thus perhaps suggest an explanation of the moie frequent occurrence of pneumonia on the right side. The death of animals, especially sheep when “ cast,” accompanied, as it is, with all the signs of pulmonary and cardiac engorgement, may be partly due to the supine position acting unfavourably on the heart, as well as on the lungs and the diaphragm ; for in quadrupeds, it must be remembered, the heart is more vertically slung from the spinal column, and they never, for any length of time, lie on their backs. This difference between man and animals in the mechanical effect of position on the heart, owing to the erect position in the former is a problem of considerable interest, especially when looked at as a process of development. In conclusion, I have to thank Professor Victor Horsley for his great kindness in performing the experiments at the Brown Institution.