A determination of the circulation rate in man at rest and at work : the regulation of the circulation / by Walter M. Boothby from the surgical service and respiration laboratory of the Peter Bent Brigham Hospital, Boston, Mass.

  • Boothby, Walter M.
Date:
[1915?]
Catalogue details

Licence: In copyright

Credit: A determination of the circulation rate in man at rest and at work : the regulation of the circulation / by Walter M. Boothby from the surgical service and respiration laboratory of the Peter Bent Brigham Hospital, Boston, Mass. Source: Wellcome Collection.

    9/40 (page 389)
    As soon as the tap is closed the observer withdraws a sample of the expired air (Sample No. 1). Then on signal the observer again opens the tap to the spirometer and the subject expires very deeply and quickly; the tap is then turned to the room air, and a sample of the second expiration is taken (Sample No. 2). It seems reasonable to assume under constant conditions of metabolism, that the gaseous content of the venous blood as it enters the lungs does not appreciably vary from moment to moment. However, during an experiment in which the breath is held marked changes would naturally follow if any part of the total blood volume could during this time effect a complete circuit and reenter the lungs a second time. The probability ■ of the presence of recirculating blood would depend on the rela¬ tionship between the total blood volume and the rapidity of the circulation rate. The blood volume of the subject of these experiments has never been determined but judging from the figures given by Douglas,13 it cannot be far from 3.8 L., allowing for the difference in weight. As the duration of the experiments at rest does not exceed twenty-five to thirty seconds and at work fifteen to eighteen seconds, and as the circulation rate under corresponding conditions is 3.4 and 9.3 litres per minute respec¬ tively, it is extremely unlikely that any blood would have time to return to the lungs except that of the coronary circulation. This latter would be of such a relatively small amount that no serious error is probably introduced by neglecting it. The abnormal condition of the subject while holding his breath during the circulation experiment affects the blood flow markedly by. altering the intrapulmonary air pressure. If this air pres¬ sure is high, less blood will tend to flow into the thoracic cage * than if the air pressure is low. The amount of this variation in intrapulmonary pressure can in large part be obviated by making the expiration after the preliminary period of such a volume that the chest walls are in a position of elastic equilibrium; 13 Douglas: The determination of the total oxygen capacity and blood volume at different altitudes by the carbon monoxide method. Jour. Physiol.. 1910, xl, 6, 471-478. j