CARDIOPULMONARY EFFECTS OF INTRAVENOUS GAS EMBOLISM; WITH SPECIAL REFERENCE TO FATE OF INTRAVASCULAR GAS BUBBLES

Abstract

To determine the graded cardiopulmonary effects and fate of pulmonary gas embolism, 11 sheep (with chronically implanted Doppler ultrasonic flow probes on pulmonary and brachiocephalic arteries) were subjected to experimental intravenous injection of nitrogen, oxygen and carbon dioxide. Three different rates of injection of each gas (0.03, 0.09 and 0.15ml/kg/min) were used for 30 minutes. Doppler ultrasonic flow probes were found to be very sensitive to the injected intravascular gas and produced characteristic "chirps." The electromagnetic blood flowmeter was insensitive to the passage of these gases. Cardiopulmonary responses include elevation of pulmonary arterial pressure, diminished cardiac output and arterial hypoxemia. Nitrogen produced the greatest response and carbon dioxide the least, correlating with differences in solubility and diffusion rates. These responses developed with a one-half time of 15-20 minutes, with recovery, following cessation of injection, at the same rate. No statistically significant changes occurred in heart rate, systemic arterial pressure, pH or Pco2. Passage of intravenous gas through the pulmonary vasculature to the systemic circulation occurred only at the 0.15ml/kg/min dosage hate. The opening of the intrapulmonary arteriovenous shunts was primarily responsible for the decrease in arterial oxygen tension and passage of gas through the lung.