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.

Children and diving, a guideline.

Scuba diving is an increasingly popular recreational activity in children and adolescents. During the dive medical examination aspects of human physiology, anatomy, and psychology, that differ between adults and children, deserve our special attention. For example, lack of mental maturity, diminished Eustachian tube function and heat loss can pose problems during diving. It is important that children who wish to take up scuba diving are seen by a dive physician, with extra attention to Eustachian tube function. In children, asthma, bronchial hyperreactivity, pulmonary hypertension, and right-to-left shunts are contra-indications for scuba diving. Attention deficit hyperactivity disorder is a relative contra-indication. This article provides a review of the current literature and presents recommendations for recreational diving in children and adolescents. These recommendations are based solely on 'expert' opinion and were accepted by the Dutch Society of Diving and Hyperbaric Medicine in 2020.

[Sir Geoffrey Marshall, anaesthetist before the term existed]. / Sir Geoffrey Marshall, anesthesioloog avant la lettre.

At the start of World War I, relatively inexperienced physicians were responsible for administering anaesthesia to severely injured soldiers in shock. Lack of knowledge, experience and proper equipment led to high mortality rates. Based on his pre-war experience in the department of respiratory physiology at Guy's Hospital in London, the British physician Geoffrey Marshall was ordered to investigate the high mortality rates. He was one of the first physicians to systematically record blood pressure, heart rate and haemoglobin level. The anaesthetic techniques of the time resulted in deep hypotension and high mortality. Marshall's main achievement was his design of a machine which could be used to reliably administer a mixture of ether, oxygen and nitrous oxide. This led to much more stable anaesthesia and a substantial decrease in mortality. After World War I, his invention became known as Boyle's machine, providing a template for all subsequent anaesthetic machines.

Opening the microcirculation: can vasodilators be useful in sepsis?

OBJECTIVE: A prominent feature of sepsis is dysfunction of the microcirculation, with impaired perfusion and regional tissue oxygenation causing a deficit in oxygen extraction. If shunting of oxygen transport past closed hypoxic microcirculatory beds is responsible for this, vasodilator therapy, which raises the driving pressure of the microcirculation and thereby promotes flow, could recruit such shunted microcirculatory units and improve tissue oxygenation. DESIGN: A literature search was conducted in Medline for evidence of this expected benefit of vasodilators in sepsis. METHODS: Studies were searched using the keyword for vasodilating drugs in combination with "sepsis," "septic," "multiple organ failure," or "critically ill patients." The search included animal and clinical investigations but only where the effects of vasodilator therapy were demonstrated by regional measures of oxygen transport variables (e.g., oxygen extraction variables, regional ischemia, microcirculatory flow or tissue oxygenation measurements). The vasodilating drugs investigated included prostacyclin, pentoxifylline, N-acetyl-cysteine, and nitric oxide donors used in animal and human sepsis. RESULTS: Prostacyclin and nitric oxide donors are the best studied vasodilating agents in experimental sepsis and have shown improved tissue perfusion and oxygen extraction. In several clinical studies prostacyclin has also been shown to have such beneficial effects. Recent studies using orthogonal polarization spectral imaging have shown microcirculatory recruitment by nitric oxide donors in hemodynamically resuscitated septic patients. Whether such therapeutic modalities aimed at recruitment of the microcirculation improve outcome, however, still has to be determined.