No abstract

Changes in cardiorespiratory function resulting from the use of three different inspiratory: expiratory ratios (1:2, 0.5:2.5, and 2:1) have been studied in normo-, hypo-and hypervolaemic dogs. Deadspace/tidal volume ratio increased slightly with the 0.5:2.5 ratio in all the states of blood volume but the changes were not statistically significant. There was a significant increase in arterial-alveolar Pco 2 difference on the 0.5:2.5 ratio in the hypervolaemic state and there was a significant reduction in the Pco s difference with the 2:1 ratio in the normovolaemic state. There was a significant reduction in arterial Po, and a significant increase in venous admixture on the 0.5:2.5 ratio in the hypervolaemic state. Cardiac output was reduced after haemorrhage and increased after overtransfusion but there were no significant changes resulting from changes in the I: E ratio within each state of blood volume.