Effects of endothelial nitric oxide synthase uncoupling on pulmonary endothelial dysfunction in rats with decompression sickness

Background: To investigate the effects of unsafe decompression on rat pulmonary endothelial function and its relevant mechanisms.Methods: Sixty male Sprague-Dawley(SD) rats were randomly divided into a control group(n=30) and a decompression sickness(DCS) group(n=30). The DCS model was established by placing the rats in the DCS group in a pressurized cabin where they were exposed to a 600 k Pa compressed air environment for 60 min, and the pressure was then reduced by 100 k Pa/min until it reached atmospheric pressure. After the surviving rats in the DCS group and the rats in the control group were anesthetized, their pulmonary arteries were stripped to test the in vitro pulmonary artery endothelium-dependent vasodilation capacity. Western blotting was used to measure the expression and dissociation of endothelial nitric oxide synthase(e NOS) in pulmonary artery tissues and all protein nitration levels in pulmonary artery tissues; reactive oxygen species(ROS) formation was measured via in vitro pulmonary artery superoxide anion probe dihydroethidium(DHE) staining.Results: After experiencing unsafe decompression, 10 of the 30 rats in the DCS group died. The pulmonary artery endothelium-dependent vasodilation capacity in the surviving rats decreased significantly(P<0.05). The difference in e NOS expression between the DCS group and the control group was statistically insignificant(P>0.05), but the ratio of e NOS monomer/dimer in the DCS group was significantly higher than that in the control group(P<0.05). All protein tyrosine nitration levels in the pulmonary artery tissues of the DCS group were significantly higher than those of the control group(P<0.05). The results of DHE staining showed that the amount of ROS formation in the pulmonary arteries of the DCS group was significantly higher than that of the control group(P<0.05).Conclusion: Unsafe decompression during a simulated submarine escape process can lead to e NOS dimer uncoupling in the pulmonary artery endothelium. The dissociated e NOS monomer cannot synthesize nitric oxide(NO) and thus affect the endothelium-dependent vasodilation capacity. The e NOS monomer can promote peroxynitrite(ONOO–) synthesis, leading to an increase in protein tyrosine nitration levels in pulmonary artery tissues and causing disorder in cell cycle regulation. The e NOS monomer can also cause an increase in the formation of ROS and thus mediate peroxidation damage.

Transcatheter closure for decompression sickness with a patent foramen ovale:A case report

A patent foramen ovale is one of the predisposing factors of neurotic decompression sickness.Transcatheter closure of a patent foramen ovale is effective in the secondary prevention of decompression sickness associated with intracardiac shunt.The size of the umbrella should not be limited to the diagnosis of a patent foramen ovale or an atrial septal defect but should be determined by the supporting force of the soft margin of the atrial septum.The surgical method of patent foramen ovale closure is the same as that of the closure of an atrial septal defect,but the closure umbrella of a patent foramen ovale is different from that of the closure umbrella of an atrial septal defect.The size of the umbrella of the right atrium is larger than that of the left atrium,and it is better to close the atrial septum.

A Short Report on Decompression Sickness Incidents in Andaman and Nicobar Islands

Objectives: Due to presence of extensively fascinating coral reef ecosystem in the continental shelf of Andaman and Nicobar Islands, people from all over the world visit these islands of India to indulge in recreational diving. An increased participation figure has also elevated the number of divers at risk for Decompression Sickness (DCS). Despite this, no scientific data are available on DCS incidents from India. Present study is aimed to evaluate the DCS incidents reported in these islands, treatment provided, and the outcome of the treatment. An attempt has also been made to calculate the approximate frequency of DCS in comparison to the participation figure. Methods: Study design is retrospective data analyses of a recompression chamber. Naval Diving Unit Port Blair has the only active decompression chamber available in the islands, and Govind Ballabh Pant Hospital Port Blair was used to collect information on DCS incidents that occurred during the mentioned period. Due to lack of authenticated generalized documents of divers’ health history and dive logs, the scanty information was gathered from the dive centres on the basis of personal interviews/communications among the SCUBA diving instructors. Results: A total of nine cases were reported during the span of last four and half years, and thus approximate frequency of DCS in Andamans was 0.2/10000 divers year. All of the patients recovered completely after receiving the Hyperbaric Oxygen Therapy (HBOT), with no residual symptoms. Conclusions: Incident rate of DCS in Andamans is lower than that in many other parts of the world;possible reason could be under-reporting of less severe DCS cases. During the study period, the number of DCS type II incidents presented for the treatment was higher than that of DCS type I incidents. HBOT proved a complete success in treating DCS cases in the island.

ACOUSTIC MEASUREMENTS BUBBLES IN BIOLOGICAL TIESSURE

An acoustic based instrument, the ABS Acoustic Bubble Spectrometer@@（ABS）, was investigated for the detection and quantification of bubbles in biological media. These include viscoelastic media （blood）, materials of varying density （bone in tissue）, non-homogenous distribution of bubbles （intravenous bubbly flow）, and bubbles migrating in tissue （decompression sickness, DCS）. The performance of the ABS was demonstrated in a series of laboratory experiments. Validation of the code was performed using a viscoelastic polymer solution, Polyox, in which the bubble size distribution and void fraction were determined by ABS measurements and with image analysis of high speed videos. These tests showed that the accuracy of the ABS was not significantly affected by viscoelasticity for bubbles smaller than 200 microns. The ABS detection and measurement of non-homogenous bubble distributions was demonstrated using a bubbly flow through a simulated vein surrounded by tissue. The scatter of acoustic signals due to bones in the acoustic pathway was also investigated. These in-vitro experiments were done using meat （beef） as a tissue simulant. Decompression experiments were done using beef meat which was held underwater at high pressure （9.9 atm） then rapidly decompressed. Bubble size distributions and void fraction calculations in these experiments were then validated using image analysis of high speed video. In addition, preliminary experiments were performed with the US Navy Medical Research Center, demonstrating the utility of the modified ABS system in detecting the evolution of bubbles in swine undergoing decompression sickness （DCS）. These results indicate that the ABS may be used to detect and quantify the evolution of bubbles in-vivo and aid in the monitoring of DCS.