On the causes of dyspnoea and cardiac failure in high altitudes / by Frank Donaldson, jr.

  • Donaldson, Frank.
Date:
[1886]
Catalogue details

Licence: Public Domain Mark

Credit: On the causes of dyspnoea and cardiac failure in high altitudes / by Frank Donaldson, jr. 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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    As to the influence of the normal respiratory move- ment upon the circulation. In any given inspira- tion the chest cavity is enlarged, negative pressure is created in the thorax; not only the lungs, but the right side of the heart and the intrathoracic portions of the systemic veins, are expanded in consequence, and the blood is drawn toward the great veins and right side of the heart. Such being the general effect of negative intrathoracic pressure, what is its effect upon the blood-flow through the lungs, upon the intrathoracic vessels, and finally upon the systemic circulation ? De Jager holds that though the negative pressure is exerted equally on the pulmonary artery and vein, the effect upon the blood in each is very different, for the walls of the pulmonary artery are much thicker than those of the pulmonary vein, and any want of pressure would be transmitted through them upon the blood much less readily. Again, the walls of the pulmonary artery are normally distended by a pressure of from 30-40 millimetres of mercury, and so the slight increase of negative pressure occurring during inspiration would probably have little or no effect in distending the pulmonary artery. On the other hand, the blood in the pulmonary vein is under little, if any, positive pressure, and so dimi- nution of pressure would distend its walls consider- ably. De Jager, therefore, holds that we would have the normal conditions during life more nearly represented if, in an artificial thorax, the pulmonary vein should be exposed to the same negative pressure as that expanding the lungs, while the pulmonary nation of his theory, I am greatly indebted to my friend, Dr. W. H. Howell, of Johns Hopkins University, who kindly allowed me to make use of his lectures on the aspiration of the thorax.