Body fat does not affect venous bubble formation after air dives of moderate severity: theory and experiment

For over a century, studies on body fat (BF) in decompression sickness and venous gas embolism of divers have been inconsistent. A major problem is that age, BF, and maximal oxygen consumption (Vo2max) show high multicollinearity. Using the Bühlmann model with eight parallel compartments, preceded by a blood compartment in series, nitrogen tensions and loads were calculated with a 40 min/3.1 bar (absolute) profile. Compared with Haldanian models, the new model showed a substantial delay in N2 uptake and (especially) release. One hour after surfacing, an increase of 14-28% in BF resulted in a whole body increase of the N2 load of 51%, but in only 15% in the blood compartment. This would result in an increase in the bubble grade of only 0.01 Kisman-Masurel (KM) units at the scale near KM = I-. This outcome was tested indirectly by a dry dive simulation (air breathing) with 53 male divers with a small range in age and Vo2max to suppress multicollinearity. BF was determined with the four-skinfold method. Precordial Doppler bubble grades determined at 40, 80, 120, and 160 min after surfacing were used to calculate the Kisman Integrated Severity Score and were also transformed to the logarithm of the number of bubbles/cm(2) (logB). The highest of the four scores yielded logB = -1.78, equivalent to KM = I-. All statistical outcomes of partial correlations with BF were nonsignificant. These results support the model outcomes. Although this and our previous study suggest that BF does not influence venous gas embolism (Schellart NAM, van Rees Vellinga TP, van Dijk FH, Sterk W. Aviat Space Environ Med 83: 951-957, 2012), more studies with different profiles under various conditions are needed to establish whether BF remains (together with age and Vo2max) a basic physical characteristic or will become less important for the medical examination and for risk assessmen

Doppler Bubble Grades After Diving and Relevance of Body Fat

SCHELLART NAM, VAN REES VELLINGA TP, VAN DIJK FJ, STERK W. Doppler bubble grades after diving and relevance of body fat. Aviat Space Environ Med 2012; 83:951-7. Background: From the literature on venous gas embolism (VGE) and decompression sickness (DCS), it remains unclear whether body fat is a predisposing factor for VGE and DCS. Therefore, this study analyses body fat (range 16-44%) in relation to precordial VGE measured by Doppler bubble grades. Also examined is the effect of age (range 34-68 yr), body mass index (BMI; range 17-34 kg . m(-2)), and a model estimate of (V) over dotO(2max) (maximal oxygen uptake; range 24-54 ml . kg(-1) . min(-1)), Methods:, (maximal oxygen uptake; range 24-54 ml . kg(-1) . min(-1)), Methods: Bubble grades were determined in 43 recreational divers after an open sea air dive of 40 min to 20 m. Doppler bubble grade scores were transformed to the logarithm of the number of bubbles/cm(2), logB, and the logarithm of the Kissman Integrated Severity Score (KISS) to allow numerical analysis. Statistical analyses were performed with Pearson's regular and partial correlations, and uni- and multivariate linear regressions. Results: For divers in their midlife (and older), the analyses indicate that neither body fat nor BMI stimulate bubble formation, since correlations were nonsignificant. In contrast, age and especially (V) over dotO(2max) appeared to determine VGE. For these types of dives it was found that logB = -1.1 + 0.02age - 0.04(V) over dotO(2max). Conclusion: Based on these data we conclude that body fat and BMI seem less relevant for diving. We recommend that medical examinations pay more attention to (V) over dotO(2max) and age, acid that international dive institutions come to a consensus regarding (V) over dotO(2max) criteri