The Journal of physiology
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The Journal of physiology · Sep 1974
Circulatory effects of deep inspirations, blocked expirations and positive pressure inflations at equal transpulmonary pressures in conscious dogs.
1. Circulatory effects of deep inspirations, blocked expirations and constant endotracheal positive pressure inflations were studied in six conscious dogs under comparable geometries of the pulmonary vascular bed, i.e. at equal transpulmonary pressures (around 10.2 cm H(2)O) and similar lung volumes.2. In order to characterize these effects, we measured beat-by-beat left and right ventricular ejections, pulmonary arterial, left atrial and aortic mean transmural pressures, and concomitant intrathoracic and tracheal pressures. ⋯ These observations suggest that the decrease in venous return (and consequently in right ventricular output) following the increase in intrathoracic pressure is the leading factor which overshadows the augmentation in left ventricular output associated with the simultaneous decrease in left ventricular outflow impedance.5. Similar experiments performed on two additional dogs in acute conditions showed the same circulatory effects before and after pharmacological blockade. These observations therefore confirm that mechanical factors play a leading part during these respiratory manoeuvres.