STATIC PRESSURE-VOLUME CURVE OF THE RABBIT LUNG AS MODIFIED BY THE INJECTION OF DEXTRAN AND VAGOTOMY

Abstract

The static pressure-volume curve of the lung was studied in eleven rabbits before, and 10 minutes after, the rapid injection of 6 per cent dextran in saline in a dose of 40 ml/kg body weight. In four of the animals the study was preceded by bilateral cervical vagotomy. In all the experimental animals, regardless of whether or not vagotomy had been performed, there was a reduction of compliance following the injection and where Pa_o2, was measured this too was found to be reduced. Autopsy showed no signs of pulmonary or peribronchial oedema. It is postulated that the rise in pulmonary artery pressure resulting from the acute expansion of total blood volume triggered an increase in the smooth muscle tone of the small airways leading to a reduction in the number of ventilated units and consequently a shift to the right of the pressure-volume curve, indicating increased transpulmonary pressure at each lung inflation. It is suggested that the reduction in Pa_o2 resulted from continuing perfusion of the non-aerated alveoli.