Decompression Studies Using Ultrasonic Imaging of Bubbles

Single bubbles ranging down in size to under 1 ¿m (less than capillary size) can be noticed, localized, and measured in ultrasonic images of intact subjects using 7.5 MHz ultrasound for which the wavelength is 200 ¿m. Subjects included humans, fish, and guinea pigs. A combined brightness modulation and deflection display was most effective. Bubble reality during decompression and association with symptoms has been demonstrated, as have asymptomatic bubbles, a tendency for bubble formation in fat, recompression bubble showers, and decompression without diving tables. In guinea pigs there were age and male-female differences in susceptibility. Adjacent tissue inert gas pressure, supersaturation, and time constant can be measured by adjusting ambient pressure until bubbles cease to grow. Present data generally favor a supersaturation rather than a phase equilibration model for bends onset. An increase in allowable supersaturation was observed when decompression was to altitude rather than to sea level. Goldfish were seen to survive bubbling that would kill the mammals studied, and some simultaneous observations by light and sound were made in transparent fish.