Adult attention-deficit/hyperactivity disorder prevalence among commercial divers in South Africa.

INTRODUCTION: Adult attention-deficit/hyperactivity disorder (ADHD) is associated with increased chance of workplace accidents, psychiatric comorbidities, other risky behaviours and sophisticated psychopharmacological treatment. These factors all contribute to a potentially complex risk profile within the commercial diving context. In order to make informed decisions regarding ADHD and commercial diving, further description of this condition among commercial divers is required. This paper reports on a study that aimed to determine the prevalence of adult ADHD among commercial divers. METHODS: The study used a self-reporting survey-type questionnaire to determine likely diagnosis, based on Diagnostic and Statistical Manual of Mental Disorders, 5th ed. criteria, in a group of 245 commercial divers in South Africa. RESULTS: Fourteen cases (5.7% of the sample) met criteria for ADHD. The majority of the cases presented with combined type, and reflected mild forms of ADHD. Adult ADHD did not appear to occur in significantly different proportions across the biographical variables of age, education or diving qualification. CONLCUSION: Based on this small survey, adult ADHD may be over-represented in commercial diving in South Africa, compared to general workplace populations. However, ADHD may not necessarily be a contra-indication to commercial diving.

Increasing prevalence of vestibulo-cochlear decompression illness in Malta - an analysis of hyperbaric treatment data from 1987-2017.

INTRODUCTION: Scuba diving is a big part of the tourism sector in Malta, and all the cases of decompression illness (DCI)are treated within the single hyperbaric referral centre in the country. METHODS: This retrospective analysis reviews all the medical records of divers with DCI in Malta within the 30-year period between 1987 to 2017 who required recompression therapy with hyperbaric oxygen. RESULTS: There were 437 discrete cases of DCI managed with recompression therapy. Amongst DCI subtypes, the prevalence of musculo-skeletal DCI is decreasing, whereas that of vestibulo-cochlear DCI is increasing. CONCLUSION: The increasing prevalence of vestibulo-cochlear DCI may be due to a change in diving practices in Malta.

Analysis of clinical outcomes of linear vs. deep stop decompression from 3.5 to 6 atmospheres absolute (350 - 600 kpa) in awake rats.

UNLABELLED: Recreational divers are introducing "deep stops" at half the depth (HD-DS) to reduce the risk of spinal DCS with only Doppler evidence to support it. Therefore this research was designed to show the effect of an HD-DS on spinal DCS manifestations by evaluating whether: (1) air diving-induced spinal DCS could be produced in awake, freely moving rats at 3.5-6.0 atm abs (350-600 kPa); and (2) whether the introduction of an HD-DS reduced spinal DCS in such a model. Fifty-one female, Wistar rats (221 to 450 g) underwent one-hour compression at 350 to 600 kPa with seven minutes of decompression with/without a five-minute DS (HD-DS / No-DS). Animals were observed for three hours. Outcomes were classified as: (1) asymptomatic; (2) breathing difficulties; (3) paralysis/weakness; (4) immobility; or (5) death. Eight animals, exposed to 385 kPa air breathing for 60 minutes followed by a three-staged decompression of 7.5 minutes, remained asymptomatic. The profile is known to produce spinal DCS in anesthetized rats. Eleven animals were then used to determine the threshold for DCS: 500 kPa. A total of 14 animals were compressed to 550 kPa (Group 1). Group 1-A (n = 8) No-DS; Group 1-B (n = 6) HD-DS; 18 were compressed to 600 kPa (Group 2). Group 2-A (n = 8) No-DS; Group 2-B (n = 10) HD-DS. RESULTS: (1) 385 kPa protocol did not produce visible DCS manifestations in awake rats. The binomial probability of no DCS in this sample size is 0.002818 for the proportion expected from a published report. The binomial probability of no fatalities is 0.005346). (2) No animals developed spinal DCS when assessed by visible paralysis/weakness or immobility, so no difference could be shown. Group 1-A: two deaths; two breathing abnormalities; four asymptomatic. Group 1-B: all asymptomatic. Difference recorded for breathing difficulties (p = 0.0483); none for fatalities (p = 0.2024). Group 2 mortality was 55% (n = 10). Group 2-A and 2-B: no difference for death (p = 0.6063) or breathing problems (p = 0.2084). CONCLUSIONS: This model could not evaluate HD-DS for the prevention of spinal DCS in rats.

Fatal respiratory failure during a "technical" rebreather dive at extreme pressure.

A diving fatality at the extreme depth of 264 m fresh water is described. The diver was equipped with an underwater video camera which recorded events leading to his death. These events corroborated predictions about respiratory complications at extreme pressure made by early researchers. Review of the video and relevant literature resulted in the following physiological interpretation: an increase in respired gas density during descent caused a progressive increase in resistance to flow in both the airways and the breathing circuit. Initially, this was associated with a shift to ventilation at higher lung volumes, a relative degree of hypoventilation, and mild permissive hypercapnia. The promotion of turbulent airway flow by increasing gas density resulted in effort-independent expiratory flow at lower flow rates than usual. The consequent inability to match ventilation to the demands of physical work at the bottom precipitated a spiraling crisis of dyspnea, increasing PaCO2, and wasted respiratory effort, thus producing more CO2. Extreme hypercapnia eventually led to unconsciousness. This tragic case provides a timely and salient lesson to a growing population of deep "technical" divers that there are physiological limitations that must be understood and considered when planning extreme dives.