A single air dive reduces arterial endothelial function in man

Abstract

During and after decompression from dives, gas bubbles are regularly observed in the right ventricular outflow tract. A number of studies have documented that these bubbles can lead to endothelial dysfunction in the pulmonary artery but no data exist on the effect of diving on arterial endothelial function. The present study investigated if diving or oxygen breathing would influence endothelial arterial function in man. A total of 21 divers participated in this study. Nine healthy experienced male divers with a mean age of 31 ± 5 years were compressed in a hyperbaric chamber to 280 kPa at a rate of 100 kPa min −1 breathing air and remaining at pressure for 80 min. The ascent rate during decompression was 9 kPa min −1 with a 7 min stop at 130 kPa (US Navy procedure). Another group of five experienced male divers (31 ± 6 years) breathed 60% oxygen (corresponding to the oxygen tension of air at 280 kPa) for 80 min. Before and after exposure, endothelial function was assessed in both groups as flow-mediated dilatation (FMD) by ultrasound in the brachial artery. The results were compared to data obtained from a group of seven healthy individuals of the same age who had never dived. The dive produced few vascular bubbles, but a significant arterial diameter increase from 4.5 ± 0.7 to 4.8 ± 0.8 mm (mean ± S.D.) and a significant reduction of FMD from 9.2 ± 6.9 to 5.0 ± 6.7% were observed as an indication of reduced endothelial function. In the group breathing oxygen, arterial diameter increased significantly from 4.4 ± 0.3 mm to 4.7 ± 0.3 mm, while FMD showed an insignificant decrease. Oxygen breathing did not decrease nitroglycerine-induced dilatation significantly. In the normal controls the arterial diameter and FMD were 4.1 ± 0.4 mm and 7.7 ± 0.2.8%, respectively. This study shows that diving can lead to acute arterial endothelial dysfunction in man and that oxygen breathing will increase arterial diameter after return to breathing air. Further studies are needed to determine if these mechanisms are involved in tissue injury following diving.

Hyperbaric Oxygen Therapy Does Not Reduce Indications for Amputation in Patients With Diabetes With Nonhealing Ulcers of the Lower Limb: A Prospective, Double-Blind, Randomized Controlled Clinical Trial

“…Its effects on vascular function in this vulnerable patient population are the least unknown. Clear evidence indicates that single, shorter exposures of healthy young divers to compressed air at slightly higher pressures are associated with evidence of significant gas emboli in venous circulation, proinflammatory changes in peripheral blood, and increases of indirect markers of endothelial injury (31)(32)(33). Therefore, the only two previously published randomized placebo-controlled trials do not satisfy criteria for an inert placebo, and their results should not be used in evaluating the efficacy of HBOT for treatment of DFUs.…”

Pre-Dive Vibration Effect on Bubble Formation After a 30-m Dive Requiring a Decompression Stop

“…Many research efforts have focused on the role of nitric oxide as a marker of the general " health " of the endothelium and as a mediator of the hydrophilic/hydrophobic properties of the endothelial wall ( 8,13,23,38 ). Furthermore, the respiration of oxygen before the dive ( 9 ), or again, a short hyperbaric exposure ( 19,24 ), seems to be capable of reducing the nitrogen content of these nuclei and exerting a protective role on postdive VGE.…”

The Impact of Repetitive Long-duration Water Immersion on Vascular Function

“…This is evidenced by the significant increase in the number of endothelial microparticles (a marker of endothelial damage) observed following compressed gas dives at 283 kPa [21]. This notion is supported by research showing that the production of reactive oxygen species (ROS) causes a reduction in endothelial function by inhibition of NO-mediated vasoregulation [22,23,24,25], and both ROS and intravascular bubble formation can result in physical endothelial cell damage [21,23,26,27,28,29].…”