Echo Imaging Techniques Determine the Size of Intravascular Bubbles inDecompression Sickness

摘要

The size of altitude-induced intravenous bubbles was determined. These bubbles,referred to as venous gas emboli (VGE), are thought to be a major factor in the onset and severity of decompression sickness (DCS). Ten volunteer subjects were monitored for altitude-induced VGE in the inferior vena cava (IVC) with a HP Sonos 1000 echo imaging system. Bubble size was determined indirectly and by in-vitro sizing methods because ultrasonic images do not necessarily represent true VGE size. Stratification of bubbles of known size in a water filled mechanical analog of the IVC determined the upper size limit, which was 300 microns in these experiments; bubbles larger than 300 microns roll along the top of the vessel. The lower size limit was the size of the smallest bubbles which the Sonos 1000 could image, determined indirectly by in-vitro microbubble flotation rates and survival times measured ultrasonically and calibrated microscopically. The diameter of the smallest VGE which echo imaging systems can detect in the IVC was found to be 30-40 microns. Used in this determination was the fact that these microbubbles are too small to float; they survive less than a minute. In conclusion, the size of the ultrasonically detected VGE in the interior of the IVC of decompressed subjects can be measured; for subjects at 29,500 ft. bubble size varied from 30-300 microns. Bubble size, Decompression sickness, Echo imaging.