The pathophysiologies of diving diseases

Acute massive posterior stroke with tonsillar herniation in a scuba diver

A transient female passenger in her 40s presented to the emergency department (ED) exhibiting drowsiness post-scuba diving. Despite normal initial vitals, she reported dizziness, sleepiness, and occipital headache. A computed tomography (CT) scan showed a severe posterior circulation acute infarction affecting various brain regions, resulting in significant mass effects and complications like 4th ventricle compression, cerebellar tonsillar herniation, and hydrocephalus. Extensive diagnostic tests, blood workup, and stroke evaluations revealed normal findings, except for an incidental patent foramen ovale (PFO). Collaboration with neurosurgery led to her transfer for life-saving extraventricular drain (EVD) insertion and posterior fossa decompression. Treatment included right-side EVD insertion, suboccipital craniectomy, and foramen magnum decompression. Postoperatively, she was extubated the next day, alert, without focal neurological deficits. Upon EVD removal, a repeat CT head scan showed regression of mass effect. She was discharged home safely after 16 days, fully ambulating.

Drinker driver flyer diver

Blood alcohol concentrations above defined levels are detrimental to cognitive performance. Empirical and published evidence suggest that nitrogen narcosis is analogous to alcohol intoxication with both impairing prefrontal cortex function. Nitrogen narcosis is also known to have been a factor in fatal accidents. To examine the effects of nitrogen narcosis, a recent publication used the Iowa Gambling Task tool, to simulate dynamic real-life risky decision-making behaviour. If the reported outcomes are corroborated in larger rigorously designed studies it is likely to provide further evidence that divers may well experience the negative effects of a 'narcotic agent', even at relatively shallow depths. These deleterious effects may occur regardless of diving experience, aptitude or professional status. In 1872, English law made it an offence to be 'drunk' whilst in charge of horses, carriages, cattle and steam engines. Understanding the danger was easy, establishing who is 'drunk' in the eyes of the court required a legal definition. Driving above a 'legal limit' for alcohol was made illegal in the United Kingdom in 1967. The limit was set at 80 milligrams of alcohol per 100 millilitres of blood. It took just short of one hundred years to get from first introducing a restriction to specific activities, whilst under the influence of alcohol, to having a clear and well-defined enforceable law. The question surely is whether our modern society will tolerate another century before legally defining safe parameters for nitrogen narcosis?