are more easily tolerated. diffusion of oxygen into the blood and tissues under hyperbaric conditions supports areas of the body which are deprived of blood flow when arteries are blocked by gas bubbles. this helps to reduce ischemic injury. the effects of hyperbaric oxygen also counteract the damage that can occur with reperfusion of previously ischemic areas; this damage is mediated by leukocytes (a type of white blood cell). complications high incidence of relapse after hyperbaric oxygen treatment due to delayed cerebral edema. epidemiology in terms of the epidemiology of air embolisms one finds that the intraoperative period to have the highest incidence. for example, vae (vascular air embolism) in neurological cases ranges up to 80%, and obgyn surgeries incidence can climb to 97% for vae. in divers the incidence rate is 7/100,000 per dive. in society and culture direct injection air embolism was one of the methods used by belgian murderer ivo poppe to kill some of his victims (the other method being valium). william davis, formerly a nurse in texas, was convicted in october 2021 of murdering four and injuring two patients by injecting air into their arterial lines following heart surgery. during opening arguments for sentencing, prosecutors told the court that they would present evidence of an additional three murders and three attempted murders. dorothy l. sayers made use of direct injection air embolism as a murder method in her 1927 lord peter wimsey mystery novel unnatural death (published in the us in 1928 as the dawson pedigree), although her description was subsequently criticised as implausible on account of the injection site and volume. air embolism was the method used by an insane nurse to euthanize seven terminally ill patients in the episode "amazing grace" of the tv series shadow chasers. near the end of young adult novel catching fire, as well as its film adaptation, protagonist katniss everdeen grabs a syringe and fills it with air, with the intention of killing peeta mellark quickly via air embolism. in plants air embolisms generally occur in the xylem of vascular plants because a fall in hydraulic pressure results in cavitation. falling hydraulic pressure occurs as a result of water stress or physical damage. a number of physiological adaptations serve to prevent cavitation and to recover from it. the cavitation may be prevented from spreading by the narrow pores in the walls between vessel elements. the plant xylem sap may be able to detour around the cavitation through interconnections. water loss may be reduced by closing off leaf stomata to reduce transpiration, or some plants produce positive xylem pressure from the roots. when xylem pressure increases, the cavitation gases may redissolve.