The Effects of Hemorrhage on Pulmonary Circulation and Respiratory Gas Exchange*†

Abstract

A close relationship between pulmonary ventilation and blood flow exists in the normal functioning of the lungs. Thus, primary alterations in one of these processes are difficult to distinguish from secondary changes in the other. In order to study these two functions in the intact animal, we have separated them by utilizing a technique which allows us to induce alterations in pulmonary blood flow while keeping ventilation constant in rate and tidal volume. This report describes changes observed in the pulmonary circulation and respiratory gas exchange of dogs in whom blood flow was decreased by hemorrhage and then restored by blood replacement.Studies on experimental animals and human subjects have indicated that all pulmonary vessels are not open at the same time (1), and that the pulmonary circulation is able to accommodate a marked increase in blood flow with little rise in the pulmonary arterial blood pressure (2-7). An increase in blood flow, then, must be accompanied by a decrease in vascular resistance, presumably due to expansion of the pulmonary bed. However, the mechanisms by which such accommodation occurs have not been fully elucidated, and questions remain as to the relative importance of physical forces, the effectiveness of vasomotor control and the significance of local pressor and chemo-reflexes. Moreover, only fragmentary

The effects of acute haemorrhage on respiration in the cat

“…2). It has been shown, however, by Bjurstedt & Coleridge (1962) and Gerst, Rattenborg & Holaday (1959) that in the dog, a fall in end-tidal carbon dioxide and an increase in arterial pH occurred when the animals were bled under constant artificial ventilation. The explanation offered by both sets of authors was essentially the same.…”

Hemorrhagic Shock in Dogs Without Major Pulmonary Changes

“…G erst el al. [8] and Wahrenbrock el al. [23] have demonstrated that Qs/Qt rises during hemorrhagic shock when lung atelectasis is present, but falls when atelectasis has disappeared.…”

“…Gas exchange remained normal, ventilation was increased with an enlarged dead space and veno-arterial shunting was reduced. Pulmonary vascular resistance was not different from the control group.Severe morphological changes have been found in the lungs of dogs submitted to hemorrhagic shock [3,6,9,21 ] but the question remains whether the respiratory function changes in relation to the anatomopathological changes or not [3,6,8,17,26]. The purpose of this study was to compare the pathological picture of the lungs with the respiratory function and pul monary hemodynamics during the acute phase of hemorrhagic shock.…”

The effects of alteration of CO2 and pH on intestinal blood flow in the cat

“…It has been shown by Gerst, Rattenborg & Holaday (1959) that there is a close relation in the dog between end-tidal Pco. and arterial blood PCO2 and that this relation has been assumed here.…”