Effect of voluntary hyperpnoea on pulmonary blood flow

Abstract

During the course of certain experiments on the mechanism of pulmonary ventilation during large breaths it was noted that the amount of oxygen absorbed was unexpectedly large. It was decided to investigate this phenomenon in detail. METHODSDeternuirations, as far as possible, were done in the early afternoon. The subject (G.H.A.) rested in the position in which the subsequent experiment was to be performed (i.e. either sitting upright or lying flat) for 10 min. The rate of oxygen uptake was then determined by spirometer or Douglas bag; and 5 min. later the experiment was performed. (In that interval, especial care was taken that the subject should refrain from activity calculated to alter the respiratory rhythm.)An experiment involved the collection of 1-S vital capacity breaths in a Douglas bag, previously rinsed with expired air. An end expiration sample of the last breath prior to collection was taken and a similar final sample taken at the end of the last collected expiration. The time between the specimens was recorded. A 101. Douglas bag was used where possible, otherwise one of standard size. The bag was fitted with a two-way tap-opened and closed by the subject between breathsconnected to a short wide mouthpiece. Although the manipulation of the tap between each breath involved the possibility of a slight loss of expired air, this was preferred to the risk of altering the results by using a valve with its inevitable slight resistance. The bag was sampled and emptied through a wet meter. Allowance has to be made for the higher oxygen contact of the alveolar air at the end of the large breaths; this accounts for a substantial proportion of the oxygen uptake during the time of the experiment.

The immediate metabolic effects of breathing carbon dioxide mixtures*

“…Alterations in the pulmonary circulation may contribute to the early increase of oxygen consumption. Armitage & Arnott (1949) noted that at the beginning of a period of voluntary hyperventilation there was an oxygen uptake amounting in their experiments to about 50 ml. This they attributed to the aspiration of venous blood into the lungs during the first deep inspirations.…”

Determination of the Pulmonary Capillary Blood Flow in Man

“…On the other hand, Armitage and Arnott 22 found a significant increase in O2 uptake when normal subjects, in a sitting position, performed successive vital capacity maneuvers; the increment was less (by two-thirds) when the subjects were tested in the supine position and failed to occur if more than two vital capacity maneuvers were performed. The authors attributed the increased O2 uptake to an increased entry of blood in the lungs during the maneuver ; in the supine position, the capacity of the lungs to accommodate additional blood would be smaller than in the upright position, and a limit would be reached promptly.…”

Determination of Pulmonary Blood Flow by Rebreathing of Soluble Inert Gases

“…Since high ventilation is known to increase the cardiac output per se [2], we believe that all the rebreathing inert gas methods for determination of capillary blood flow are erroneous in the sense that they measure the capil lary blood flow in an unsteady state situation, the cardiac output rising during the maneuver. Furthermore, the value can hardly be compared with values obtained by other methods that are not performed simultaneously, and cannot be extrapolated to the situation prevailing before the rebreathing maneuver.…”

“…34], Two sources of error have received little attention in previous analyses: (a) During the rebreathing maneuvers, all methods consider lung and re-breathing bag as an homogeneous system. Since the blood flow is contin uously taking inert gas during the procedure, bag and lung should have the same composition only if ventilation is infinite, and obviously this is not the case, (b) Since high ventilation is known to increase per se pulmo nary blood flow [2], the high ventilation performed during the rebreathing should influence the calculated pulmonary capillary blood flow. The present report describes a modification of the analysis of the data that takes the difference in gas concentration between rebreathing bag and lung into con sideration.…”