Cardiovascular risk assessment in divers: Toward safer diving

Similar to aviation, diving is performed in an environment in which acute incapacitation may lead to a fatal outcome. In aeromedicine, a pilot is considered "unfit to fly" when the cardiovascular event risk exceeds one percent per annum, the so-called 1% rule. In diving no formal limits to cardiovascular risk have been established. Cardiovascular risk of divers can be calculated using the modified Canadian Cardiovascular Society (CCS) Risk of Harm formula: risk of harm (RH: cardiovascular fatality rate per year during diving: number × 10-⁵/divers/year) = time diving (TD: number of dives × 10-⁴) × sudden cardiac incapacitation (SCI: cardiovascular diver event rate per year (number × 10-⁵/year). The SCI and thus the RH are strongly dependent on age. Using the CCS criterion for RH, 5 × 10-⁵ divers/year, and considering an average of 25 dives per year per diver, the calculated maximum acceptable SCI is 2%/year, consistent with current practice for dive medical examinations. If the SCI were to exceed 2%/year, a diver could be considered "unfit to dive," which could particularly benefit older (≥ 50 years) divers, in whom cardiovascular risk factors are often not properly treated. For the prevention of fatal diving accidents due to atherosclerotic cardiovascular disease, a dive medical examination is of limited value for young (≺ 50 years) divers who have no cardiovascular risk factors. Introducing a cardiovascular risk management system for divers may achieve a reduction in fatal diving accidents that result from cardiovascular disease in older divers engaged in both recreational and professional diving.