CARDIOPULMONARY CHANGES WITH MODERATE DECOMPRESSION IN RATS

Sprague-Dawley rats were compressed to 616 kPa (a) for 120 min then de compressed at 38 kPa/min to assess the cardiovascular and pulmonary re sponses to moderate decompression stress. In one series of experiments the rats were chronically instrumented with Doppler ultrasonic probes for simultaneous measurement of blood pressure, cardiac output, heart rate, left and right ventricular wall thickening fraction, and Venous bubble detection. Data were collected at baseline, throughout the com pression/decompression protocol, and for 120 min post decompression. Z n a second series of experiments the pulmonary responses to the decomp ression protocol were evaluated in non-instrumented rats. Analyses inc luded blood gases, pleural and bronchoalveolar lavage (BAL) protein an d hemoglobin concentration, pulmonary edema, BAL and lung tissue phosp holipids, lung compliance, and cell counts. Venous bubbles were direct ly observed in 90% of the rats where immediate post-decompression auto psy was performed and in 37% using implanted Doppler monitors. Cardiac output, stroke volume, and right ventricular wall thickening fraction s were significantly decreased post decompression, whereas systemic va scular resistance was increased suggesting a decrease in venous return . BAL Hb and total protein levels were increased 0 and 60 min post dec ompression; pleural and plasma levels were unchanged. BAL white blood cells and neutrophil percentages were increased 0 and 60 min post deco mpression and pulmonary edema was detected. Venous bubbles produced wi th moderate decompression profiles give detectable cardiovascular and pulmonary responses in the rat.