Small amounts of venous gas embolism cause delayed impairment of endothelial function and increase polymorphonuclear neutrophil infiltration.

Gas bubbles from decompression and gas embolization lead to endothelial dysfunction and mechanical injury in the pig, rabbit and lamb. In the study presented here, 0.01 ml air/min/kg was infused through a catheter into the jugular vein in 12 rabbits for 60 min. The endothelial response was measured using tension measurements in the blood vessel wall, and morphological changes where quantified using light microscopy and image processing. Percent lung water content was calculated and used to estimate the severity of pulmonary oedema. The infusion led to a significant decrease in the acetylcholine-mediated endothelial-dependent vasodilatation in the pulmonary artery 6 h after the infusion (6-h group, n = 6). A decrease in substance-P-mediated endothelial-dependent vasodilatation was also detected. No changes where seen in a group of rabbits examined 1 h after infusion (l-h group, n=6). The impaired endothelial-dependent vasodilatation caused by the bubbles is probably biochemical in origin, since no visible changes were seen in the endothelial layer. A significant increase in polymorphonuclear neutrophils was observed in the 6-h group compared to the l-h group. This study demonstrates that small numbers of bubbles, corresponding to "silent bubbles", lead to an impairment of the endothelial-dependent vasoactive response.