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Divers suffering decompression illness (DCI) increasingly undertake high altitude travel after hyperbaric treatment. Anecdotal evidence suggests hyperbaric chambers give widely differing advice regarding the safe time to fly after treatment (TFAT), resulting in possible health, socio-economic and insurance implications. Thirty two chambers were contacted to determine current trends in advice on TFAT and the rationale behind these trends. Twenty three (72%) chambers responded of which five returned incomplete data, and 18 returned data fulfilling all the criteria. This study collates the current advice given by these 18 chambers, and the basis on which it is given. Only one of the responding chambers had no relevant guidelines.
Advised TFAT differed widely, varying from immediately to six weeks. Seven chambers gave advice based on Divers Alert Network (DAN) recommendations, two based on research, and the remaining chambers relied on local staff advice based on their own experience. Only six chambers followed up divers after treatment, leading to a paucity of data regarding complication and recurrence rates following ‘return home’. Repeated contact with chambers revealed many units kept inadequate records, or did not have the staffing available to collate information for this study, limiting the success of this type of research. Guidelines on TFAT for DCI vary radically between chambers, and are rarely evidence based.
Some studies involving women taking the combined oral contraceptive pill (COCP) have on occasion assumed the COCP group to have a rigid 28-day pharmaceutically driven cycle. Anecdotal evidence suggests otherwise, with many women adjusting their COCP usage to alter the time between break-through bleeds for sporting and social reasons. A prospective field study involving 533 scuba diving females allowed all menstrual cycle lengths (COCP and non-COCP) to be observed for up to three consecutive years (St Leger Dowse et al. 2006). A total of 29% of women were COCP users who reported 3,241 cycles. Of these cycles, only 42% had a rigid 28-day cycle, with the remainder varying in length from 21 to 60 days.
When performing studies involving the menstrual cycle, it should not be assumed that COCP users have a rigid confirmed 28-day cycle and careful consideration should be given to data collection and analysis. The effects of differing data interpretations are shown.
Our understanding of the effects of scuba diving on diabetes mellitus (DM) or the effect of DM on a diver’s ability to dive safely is limited. Most diving authorities worldwide consider insulin-dependent diabetes mellitus (IDDM) to be a contraindication to scuba diving. Divers taking oral hypoglycaemic agents are considered to be at risk of hypoglycaemia in the water, while those controlled using non-hypoglycaemic agents, or diet alone are thought by some authorities to be safe to dive.
Evidence exists that there are divers with DM who dive safely, and have done so for many years, either using insulin or hypoglycemic tablets.
The aim of this survey is to observe, over a period of time, the ordinary diving habits and histories of recreational divers, as opposed to the “monitored” and controlled diving of recreational divers with DM in some studies. It also examines the rates at which divers with DM and divers without DM cease to dive and whether any significant differences exist between them. Preliminary results have been reported elsewhere.
Data are presented from the first 11 years of this survey (1991-2001).
No human data, investigating the effects on the fetus of diving, have been published since 1989. We investigated any potential link between diving while pregnant and fetal abnormalities by evaluating field data from retrospective study No.1 (1990/2) and prospective study No.2 (1996/2000). Some 129 women reported 157 pregnancies over 1,465 dives. Latest gestational age reported while diving was 35 weeks. One respondent reported 92 dives during a single pregnancy, with two dives to 65 m in the 1st trimester. In study No.2 490% of women ceased diving in the 1st trimester, compared with 65% in the earlier
study. Overall, the women did not conduct enough dives per pregnancy, therefore no significant correlation between diving and fetal abnormalities could be established. These data indicate women are increasingly observing the diving industry recommendation and refraining from diving while pregnant. Field studies are not likely to be useful, or the way forward, for future diving and pregnancy research. Differences in placental circulation between humans and other animals limit the applicability of animal research for pregnancy and diving studies. It is unlikely that the effect of scuba diving on the unborn human fetus will be established.
There is dispute as to whether paradoxical gas embolism is an important aetiological factor in neurological decompression illness, particularly when the spinal cord is affected. We performed a blind case-controlled study to determine the relationship between manifestations of neurological decompression illness and causes in 100 consecutive divers with neurological decompression illness and 123 unaffected historical control divers. The clinical effects of neurological decompression illness (including the sites of lesions and latency of onset) were correlated with the presence of right-to-left shunts, lung disease and a provocative dive profile.
The prevalence and size of shunts determined by contrast echocardiography were compared in affected divers and controls. Right-to-left shunts, particularly those which were large and present without a Valsalva manoeuvre, were significantly more common in divers who had
neurological decompression illness than in controls (P 0.001). Shunts graded as large or medium in size were present in 52 % of affected divers and 12.2 % of controls (P 0.001). Spinal decompression illness occurred in 26 out of 52 divers with large or medium shunts and in 12 out of 48 without (P 0.02). The distribution of latencies of symptoms differed markedly in the 52 divers with a large or medium shunt and in the 30 divers who had lung disease or a provocative dive profile. In most cases of neurological decompression illness the cause can be determined by taking a history of the dive profile and latency of onset, and by performing investigations to detect a right-to-left shunt and lung disease. Using this information it is possible to advise divers on the risk of returning to diving and on ways of reducing the risk if diving is resumed. Most cases of spinal decompression illness are associated with a right-to-left shunt.
