Ascent Rate and Circulating Venous Bubbles in Recreational Diving

The aim of this study was to assess the effect of the ascent rate on the production of venous circulating bubbles during the decompression following a recreational dive. Twenty-eight recreational divers performed two open water dives at 35 m during 25 minutes. Ascent rate up to the decompression stop was in one case 9 meter per minute (m/min) and in the other case 17 m/min. Circulating venous bubbles were screened using continuous wave Doppler every 10 minutes during one hour after surfacing. Bubbles Doppler signals were graded according to the Spencer scale (from 0 to IV), and the Kisman integrated severity score (KISS) was calculated. Statistical analysis demonstrated a significantly higher bubbles grade and a significantly higher KISS following the rapid decompression compared to the slow one (respectively p = 0.001 and p = 0.0001). In conclusion, these results demonstrate that a 9 m/min ascent rate is safer than a 17 m/min one.