Exogenous nitric oxide and bubble formation in divers.
OBJECTIVE
Prevention of bubble formation is a central goal in standard decompression procedures. Previously we have shown that exercise 20-24 h prior to a dive reduces bubble formation and increases survival in rats exposed to a simulated dive. Furthermore, we have demonstrated that nitric oxide (NO) may be involved in this protection; blocking the production of NO increases bubble formation while giving rats a long-lasting NO donor 20 h and immediately prior to a dive reduces bubble formation. This study determined whether a short-lasting NO donor, nitroglycerine, reduced bubble formation after standard dives and decompression in man.


METHODS
A total of 16 experienced divers were randomly assigned into two groups. One group performed two dives to 30 m of seawater (msw) for 30 min breathing air, and performed exercise at an intensity corresponding to 30% of maximal oxygen uptake during the bottom time. The second group performed two simulated dives to 18 msw for 80 min breathing air in a hyperbaric chamber, and remained sedentary during the bottom period. The first dive for each diver served as the control dive, whereas the divers received 0.4 mg of nitroglycerine by oral spray 30 min before the second dive. Following the dive, gas bubbles in the pulmonary artery were recorded using ultrasound.


RESULTS
The open-water dive resulted in significantly more gas bubbles than the dry dive (0.87 +/- 1.3 vs 0.12 +/- 0.23 bubbles per square centimeter). Nitroglycerine reduced bubble formation significantly in both dives from 0.87 +/- 1.3 to 0.32 +/- 0.7 in the in-water dive and from 0.12 +/- 0.23 to 0.03 +/- 0.03 bubbles per square centimeter in the chamber dive.


CONCLUSIONS
The present study demonstrates that intake of a short-lasting NO donor reduces bubble formation following decompression after different dives.
Dujić
Zeljko
Z
Departments of Physiology, University of Split School of Medicine, Split, Croatia. zdujic@bsb.mefst.hr
Palada
Ivan
I
Valic
Zoran
Z
Duplancić
Darko
D
Obad
Ante
A
Wisløff
Ulrik
U
Brubakk
Alf O
AO
D000328:Adult; D003665:Decompression Sickness / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000517:prevention & control*; D004242:Diving / Q000502:physiology*; D005740:Gases / Q000097:blood*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006931:Hyperbaric Oxygenation; D008297:Male; D020030:Nitric Oxide Donors / Q000008:administration & dosage*; D005996:Nitroglycerin / Q000008:administration & dosage*; D010101:Oxygen Consumption / Q000502:physiology; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D014463:Ultrasonography
D005740:Gases; D020030:Nitric Oxide Donors; D005996:Nitroglycerin