Separation of basic parameters of decompression using fingerling salmon.

The experimental limitations inherent in use of air-breathing vertebrates for studies of decompression are chiefly due to the difficulty in estimating supersaturation levels associated with both symptoms of decompression sickness and bubble formation. The difficulty is because gas elimination begins upon reduction of pressure and therefore complicates any estimates of the supersaturations that promoted the bubbles or symptoms, or both, in the first place. Use of physostomatous fish such as salmonid fingerlings easily available from hatcheries allows decompression of both fish and surrounding water, thereby minimizing gas tension gradients from the fish to the water and the water to the fish. Depending upon the experimental conditions imposed, the important physical properties such as diffusivity and solubility of different diving gases, H2, Ne, He, and N2, can be separated or combined parametrically. Results of these studies indicate that initial bubble formation in vivo is relatively independent of solubility, whereas the bubble growth phase is more dependent on gas concentration.