Cardiovascular risk assessment in divers: Toward safer diving

Abstract

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.

SCUBA Diving in Adult Congenital Heart Disease

“…Professional diving organizations (military, police, fire brigade) usually require an exercise capacity of 13 METs (peak VO2 40 mL/kg/min) [ 17 ]. Patients (whether with ACHD) who do not meet an exercise capacity of 25 mL/min/kg are conventionally advised not to dive, while patients with a VO2 max between 25 and 40 (men) or 25 and 35 (women) are advised to engage in non-strenuous diving or fitness optimization prior to commencing diving [ 18 ].…”

“…ACHD patients with a reduced exercise capacity should realize that they are not suitable for participating in all types of diving at all places. They should be advised to avoid diving in circumstances requiring strenuous exercise, such as when there are strong currents, cold water, difficult entry into and exit from the water, carrying heavy equipment such as twinsets and decompression cylinders, stress dives, cave and wreck diving, technical diving and being an instructor for other divers [ 18 ].…”