Decompression sickness in diving is recognized as a multifactorial phenomenon, depending on several factors, such as decompression rate and individual susceptibility. The Doppler ultrasonic detection of circulating venous bubbles after diving is considered a useful index for the safety of decompression because of the relationship between bubbles and decompression sickness risk. The aim of this study was to assess the effects of ascent rate, age, maximal oxygen uptake (VO(2 max)), and percent body fat on the production of bubbles after diving. Fifty male recreational divers performed two dives at 35 m during 25 min and then ascended in one case at 9 m/min and in the other case at 17 m/min. They performed the same decompression stops in the two cases. Twenty-eight divers were Doppler monitored at 10-min intervals, until 60 min after surfacing, and the data were analyzed by Wilcoxon signed-rank test to compare the effect of ascent rate on the kinetics of bubbles. Twenty-two divers were monitored 60 min after surfacing. The effect on bubble production 60 min after surfacing of the four variables was studied in 47 divers. The data were analyzed by multinomial log-linear model. The analysis showed that the 17 m/min ascent produced more elevated grades of bubbles than the 9 m/min ascent (P < 0.05), except at the 40-min interval, and showed relationships between grades of bubbles and ascent rate and age and interaction terms between VO(2 max) and age, as well as VO(2 max) and percent body fat. Younger, slimmer, or aerobically fitter divers produced fewer bubbles compared with older, fatter, or poorly physically fit divers. These findings and the conclusions of previous studies performed on animals and humans led us to support that ascent rate, age, aerobic fitness, and adiposity are factors of susceptibility for bubble formation after diving.

No abstract

Decompression sickness (DCS) is recognized as a multifactorial phenomenon depending on several individual factors, such as age, adiposity, and level of fitness. The detection of circulating venous bubbles is considered as a useful index for the safety of a decompression, because of the relationship between bubbles and DCS probability. The aim of this work was to study the effects of individual variables which can be assessed non invasively, on the grades of bubbles detected 60 min, after diving by means of Doppler monitoring, in a sample of 40 male recreational scuba divers. The variables investigated were: age, weight, maximal oxygen uptake (VO2max) and percentage of body fat (%BF). Bubble signals were graded according to the code of Spencer. The relationships between the bubble grades (BG) and the variables investigated were studied using two methods: the differences between the average values of each variable at each BG were analyzed by the Scheffe test. Then we performed the non-parametric Spearman correlation analysis. Significant differences (P < 0.05) were found (Scheffe test) between average values of the variables at grade 0 and 3 (age: P = 0.0323; weight: P = 0.0420; VO2max: P = 0.0484), except for %BF (P = 0.1697). Relationships with P < 0.01 were found (Spearman correlation) between BG and the variables: age: p = 0.486, P = 0.0024; weight: p = 0.463, P = 0.0039; VO2max: p = -0.481, P = 0.0027; except for %BF: p = 0.362, P = 0.0237. This work showed that bubble production after hyperbaric exposures depends on several individual factors. The effects of age, weight and VO2max are more significant than the effect of %BF. We concluded that to take into account such variables in decompression tables and diving computer programs should allow to adapt the decompression procedures to individual risk factors and reduce the DCS probability.

Overall, we observed fewer circulating bubbles in women than in men after an open sea SCUBA dive. This difference disappeared in the postmenopausal women.

The aim of this study was to determine the utility of pulsed Doppler and 2D echocardiography for the detection and the quantification of circulating bubbles after decompression. Twenty-three sport divers performed 60 SCUBA dives (mean 32 msw). An evaluation of circulating bubbles was performed using 2D images one hour after diving. Circulating bubbles were also detected with pulsed Doppler. The sample volume was placed in the outflow area of the right ventricle 1-2 cm below the pulmonary valve. 2D echocardiography showed circulating bubbles in right cavities of the heart in 32 cases. Short axis parasternal view and right cavities long axis view were the best incidences. Pulsed Doppler confirmed the results in these 32 cases and detected circulating bubbles in seven other cases. Isometric contraction of muscle limb must be performed to increase the sensitivity of detection. The count of the bubbles may be evaluated when using a combination of Spencer's and Powell's grading. We conclude that 2D echocardiography is less accurate than pulsed Doppler in the detection of circulating bubbles after decompression. Further studies are needed to compare pulsed Doppler guided by 2D echocardiography to continuous Doppler for the detection of circulating bubbles.