title: High incidence of venous and arterial gas emboli at rest after trimix diving without protocol violations.
abstract: SCUBA diving is associated with generation of gas emboli due to gas release from the supersaturated tissues during decompression. Gas emboli arise mostly on the venous side of circulation, and they are usually eliminated as they pass through the lung vessels. Arterialization of venous gas emboli (VGE) is seldom reported, and it is potentially related to neurological damage and development of decompression sickness. The goal of the present study was to evaluate the generation of VGE in a group of divers using a mixture of compressed oxygen, helium, and nitrogen (trimix) and to probe for their potential appearance in arterial circulation. Seven experienced male divers performed three dives in consecutive days according to trimix diving and decompression protocols generated by V-planner, a software program based on the Varying Permeability Model. The occurrence of VGE was monitored ultrasonographically for up to 90 min after surfacing, and the images were graded on a scale from 0 to 5. The performed diving activities resulted in a substantial amount of VGE detected in the right cardiac chambers and their frequent passage to the arterial side, in 9 of 21 total dives (42%) and in 5 of 7 divers (71%). Concomitant measurement of mean pulmonary artery pressure revealed a nearly twofold augmentation, from 13.6 ± 2.8, 19.2 ± 9.2, and 14.7 ± 3.3 mmHg assessed before the first, second, and the third dive, respectively, to 26.1 ± 5.4, 27.5 ± 7.3, and 27.4 ± 5.9 mmHg detected after surfacing. No acute decompression-related disorders were identified. The observed high gas bubble loads and repeated microemboli in systemic circulation raise questions about the possibility of long-term adverse effects and warrant further investigation.
authors.affiliation: Department of Physiology, University of Split School of Medicine, Soltanska 2, 21000 Split, Croatia.
authors.forename: Marko
authors.initials: M
authors.lastname: Ljubkovic
authors.forename: Jasna
authors.initials: J
authors.lastname: Marinovic
authors.forename: Ante
authors.initials: A
authors.lastname: Obad
authors.forename: Toni
authors.initials: T
authors.lastname: Breskovic
authors.forename: Svein E
authors.initials: SE
authors.lastname: Gaustad
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Dujic
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D001794:Blood Pressure; D004242:Diving / Q000009:adverse effects*; D018618:Echocardiography, Doppler, Color; D018619:Echocardiography, Doppler, Pulsed; D004618:Embolism, Air / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D054092:Foramen Ovale, Patent / Q000150:complications / Q000000981:diagnostic imaging; D006371:Helium / Q000008:administration & dosage / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000008:administration & dosage / Q000009:adverse effects*; D010100:Oxygen / Q000008:administration & dosage / Q000009:adverse effects*; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D013997:Time Factors; D014680:Veins / Q000000981:diagnostic imaging
chemical_list: D006371:Helium; C045257:trimix; D009584:Nitrogen; D010100:Oxygen