Effects of tetrahydrobiopterin on venous bubble grade and acute diving-induced changes in cardiovascular function.

Introduction: Self-contained underwater breathing apparatus diving reduces cardiovascular function and increases pulmonary artery pressure (PAP) up to 3 days after a single dive. Acute antioxidants partially attenuated arterial endothelial dysfunction, whereas cardiac and PA functions were unaffected. We tested the hypothesis that acute tetrahydobiopterin (BH(4)), as a cofactor of endothelial nitric oxide (NO) synthase, reduces bubble grade (BG) and attenuates alteration in cardiovascular function after diving because of increased NO bioavailability.

Materials And Methods: Mean PAP (mPAP), PA acceleration time and right ventricle ejection time, left ventricle ejection fraction (LV-EF) and BG were measured after oral placebo (P), vitamin C (C) or a combination of vitamin C and BH(4) (BH(4)) in a randomized, placebo controlled trial before and after field dive to 30 m of sea water for 30 min bottom time.

Results: Eight recreational divers performed three dives with a 3-days period between them. Regarding the primary hypothesis, no difference was observed between post-dive changes in BG (2.1 +/- 2.2 bubbles cm(-2) for P, 3.4 +/- 3.9 for C and 3.6 +/- 2.1 for BH(4)), mPAP (25.6 +/- 6.5 mmHg for P, 25.9 +/- 8.6 for C and 22.6 +/- 3.5 for BH(4)) and LV-EF (62.6 +/- 4.6% for P, 61.4 +/- 3.9 for C and 61.6 +/- 3.7 for BH(4)) with all three conditions.

Conclusion: This suggests that co-administration of BH(4) and vitamin C does not improve heart and pulmonary artery function after diving.