Marguerite St Leger Dowse, Steve Shaw, Christine Cridge, Gary Smerdon (2011) The use of drugs by UK recreational divers: illicit drugs
Summary: This study investigated the prevalence and type of illicit drugs used by recreational divers in the United Kingdom (UK). Anonymous questionnaires entitled "The Health of Divers" were circulated via UK dive clubs, dive schools, dive shows and conferences. General health questions included anxiety, depression and panic attacks, alcohol use, cigarette smoking, illicit drug use since learning to dive and closest time to a dive. 479 divers responded (66% males and 34% females) with 22% having used one or more illicit drug since learning to dive, reporting the use of benzodiazepines, amphetamines, cocaine, ecstasy, LSD, cannabis, heroin, and magic mushrooms. Illicit drugs had been used by 3.5% of respondents in the last 12 months, and 3% in the last month. Cannabis, cocaine and ecstasy use was reported within 6 hours of a dive. Analysis also showed a relationship between illicit drug use and depression, and also between illicit drug use and anxiety. The study supported anecdotal reports that recreational divers use a range of illicit drugs; and the significant relationship between illicit drug use and depression and anxiety also supported the literature in non-diving populations.
Download: dowse-illicit-drugs-diving.pdf (180KB)

Marguerite St Leger Dowse, Christine Cridge, Gary Smerdon (2011) The use of drugs by UK recreational divers: prescribed and over the counter medications
Summary: Anecdotally it is known divers regularly take medications around the time of their diving activities for different health conditions, possibly ignoring the recommendations not to do so. As part of a study of illicit drug use in sport divers, secondary data regarding the use of prescribed and over the counter medications were gathered. Anonymous questionnaires entitled "The Health of Divers" were circulated. Divers were asked if they were currently taking medication prescribed by a physician, if they had ever taken any over the counter drugs within six hours before a dive, and to give details. 531 divers responded (68% male, 32% female), with over the counter medication used by 57% of the respondents 6 hours or less before diving. Analgesics were the most commonly reported, with the use of decongestants, the next most regularly reported. Prescribed medications were used by 23% of respondents, with 10% reporting the use of cardiovascular drugs. The majority of the cardiovascular medication was for primary disease prevention; however some drugs only used in the treatment of symptomatic cardiovascular disease were also reported. The range of prescribed medications reported in this study was broad and suggested a need for further investigation regarding medication use and fitness to dive.
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Williams STB (2010) The role of hyperbaric oxygen therapy in trauma. Trauma 12:13-20
Summary: This review explains the method of action of hyperbaric oxygenation (HBO) therapy and examines the evidence for its use in trauma. Methods of delivery, complications and contra-indications are discussed. It is acknowledged that there are few controlled trials which evaluate the efficacy of HBO in this indication; supporting evidence for its efficacy is mainly in the form of case reports, or by implication from laboratory and animal work. Lack of evidence may not equate to lack of efficacy, but may reflect the difficulties in coordinating clinical trials involving critically ill patients and a complex treatment modality, the availability of which is not widespread. The adjunctive use of HBO has shown promising results in the treatment of crush injury. Consideration of tissue pathophysiology suggests that such an approach may also offer improved outcomes in the broader spectrum of trauma scenarios involving marginally viable tissues with compromised perfusion.
Download: williams_trauma.pdf (188KB)

Williams STB, Davies A and Bryson P. (2009) Chronic Regional Pain Syndrome After Subtalar Arthrodesis Is Not Prevented by Early Hyperbaric Oxygen. Pain Physician 12:E335-E339
Summary: Subtalar arthrodesis was performed on a 48-year-old, non-insulin-dependent diabetic with a history of chronic ankle instability and lateral ankle pain. In the early post-operative period he presented as an emergency with an infection at the operative site. This was treated with 2 returns to the operating theatre for washout and debridement. His wounds were left open and at 3 weeks after emergency admission he was referred for adjunctive hyperbaric oxygen (HBO) therapy to aid healing by secondary intention. He received a total of 19 hyperbaric sessions, at a pressure of 2.2 ATA, one treatment per day for 5 days a week.
Shortly after commencing HBO therapy his ankle became increasingly painful, despite the introduction of analgesia. By 7 weeks after emergency admission his wounds had virtually healed but hyperesthesia persisted over the dorsum of the foot. A computerized tomography scan at 5½ months post-operatively showed satisfactory joint fusion and revealed no evidence of infection. Symptoms and signs at this time were compatible with a diagnosis of chronic regional pain syndrome (CRPS).
There is published evidence to suggest that HBO therapy may be a useful modality in the treatment of established CRPS. Here, we seek to publicize a case in which early treatment with HBO for another indication did not prevent the simultaneous development of CRPS Type 1.
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Shaw FL, Winyard PG, Smerdon GR, Bryson PJ, Moody AJ, Eggleton P. (2009) Hyperbaric oxygen treatment induces platelet aggregation and protein release, without altering expression of activation molecules. Clin Biochem. Vol. 42, No.6, pp. 467-76.
Summary: This study investigated the effect of hyperbaric oxygen (HBO) on platelet physiology.
Human platelets were exposed to HBO (97.7% O2, balance CO2 at 2.2 ata) or control (CON; 5% CO2, balance air at 1 ata) for 90 min, and analyzed for aggregation, protein release, NO production, and activation.
HBO induced 29.8±3.0% of platelets to aggregate compared with CON (5.5±0.9%). Proteins observed to be released in greater abundance from HBO- compared with CON-treated platelets included 14-3-3 zeta and ?-2-macroglobulin. Release of NO by platelets was unaffected following exposure to HBO, as was platelet activation as measured by surface expression of PECAM-1, CD62P and the activated form of ?IIB?IIIa.
Exposure to HBO induced both platelet aggregation and protein release. Further study will better define the precise mechanisms and effects of HBO on platelet activation.
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Yuan J, Handy RD, Moody AJ, Bryson P. (2009) Response of blood vessels in vitro to hyperbaric oxygen (HBO): Modulation of VEGF and NO(x) release by external lactate or arginine. Biochim Biophys Acta. Vol. 1787, No. 7: pp. 828-34.
Summary: Hyperbaric oxygen therapy (HBO) is suggested to promote angiogenesis during wound healing, but the mechanisms involved are not understood. This study used a novel isolated blood vessel preparation to explore the effects of air, normobaric oxygen or hyperbaric oxygen (2.2 ATA for 90 min) on the angiogenesis factor, vascular endothelial growth factor (VEGF), nitrite and nitrate (NOx), lactate dehydrogenase (LDH) and lactate release from the tissue in normal Krebs Ringer, and the Ringer supplemented with either L-arginine, or 15 mM lactate to mimic a wound environment, or both (L-arginine+lactate). The in vitro blood vessel preparation remained viable during all experiments. There were no effects of HBO treatment on any of the parameters measured in normal Krebs Ringer, but some treatment-dependent effects were observed in supplemented Krebs Ringer. In the lactate supplemented Krebs Ringer, medium LDH levels increased in response to either normobaric oxygen (NBO) or HBO, compared to air alone. There were also small, but statistically significant increases in total glutathione due to HBO treatment, compared to NBO or air in the lactate supplemented medium, and in the combined supplement. There were no effects of HBO on NOx, changes in external medium lactate levels, or tissue VEGF in any of the Krebs Ringers tested. However, post treatment increases in VEGF were observed in the lactate supplemented medium, and for lactate release into the medium for the combined supplement. We conclude that HBO does not cause NO or VEGF production from the blood vessel in normal Krebs Ringer, but the data from supplemented medium show that the response of the tissue is subtly affected by the chemical environment around the blood vessel, and the tissue is more responsive to HBO when wound conditions are mimicked.
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Bishop A. (2008) Role of oxygen in wound healing. J Wound Care. Vol. 17, No. 9,: pp. 399-402.
Summary: Research has identified the importance of oxygen in all aspects of the healing process. It helps to promote angiogenesis and collagen synthesis, ensure effective leucocyte and fibroblast functioning, and produce growth factors and reactive oxygen species (ROS). This overview examines the evidence on the role of oxygen in acute wound healing.
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Harding SA, Hodder SC, Courtney DJ, Bryson PJ. (2008) The Impact of Peri Operative Hyperbaric Oxygen Therapy on the Quality of Life of Maxillofacial Patients who undergo surgery in irradiated fields. International Journal of Oral & Maxillofacial Surgery. Vol. 37, No. 7,: pp. 617-624
Summary: From 2001 to 2005, 66 patients referred for perioperative hyperbaric oxygen therapy (HBO2) for debridement of necrotic tissue or prevention of radionecrosis were assessed with quality of life measures, before and after completion of HBO2 and surgery. The Medical Outcomes Short Form 36 (SF-36) and Hospital Anxiety and Depression Scale (HADS) showed no significant changes. The European Organisation for Research and Treatment of Cancer Core (EORTCC30) questionnaire showed significant improvement in pain, global health, and dyspnoea (p = 0.011; p = 0.027; p = 0.008, respectively). The Head and Neck submodule (H&N35) identified significant improvements in teeth, dry mouth and social contact (p = 0.002; p = 0.038; p = 0.029, respectively). The University of Washington Scale (UW), showed significant changes in relation to chewing and shoulders (p = 0.031; p = 0.047). When sub-group analysis using 'osteoradionecrosis' and 'dental extraction or implants' was performed on the EORTC and UW data, variations in the patterns of significance were found. Adjunctive HBO2 should be considered for the treatment and prevention of some of the long-term complications of radiotherapy.
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Dowse MS, Gunby A, Moncad R, Fife C, Smerdon G, Bryson P. (2007) The combined oral contraceptive pill and the assumed 28-day cycle. J Obstet Gynaecol. Vol 27 no. 5 pp.481-4
Summary: 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.
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Williams, STB, Prior, FGR and Bryson, P. (2007) Hematocrit change in tropical scuba divers. Wilderness and Environmental Medicine vol 18 no. 1 pp. 48-53
Summary: Direct evidence that dehydration results from scuba diving is scanty. Increased hematocrit (Ht) is a commonly used proxy measure for dehydration. This study sought evidence that an increase in Ht occurs over the course of a scuba dive in tropical conditions. As a secondary outcome, evidence was sought that the degree of Ht increase is correlated to pressure exposure. Twenty male and 21 female scuba divers were recruited at a remote tropical dive site. Water temperature was 30°C (+/- l°C). Each diver gave venous blood relating to 1 dive only. Mean maximum dive depth was 13.6 m (+/- 3.7 m [SD]) and mean duration 39.5 minutes (+/- 4.5 minutes [SD]) using air as the breathing gas. Blood was taken at a mean of 12.4 minutes (+/- 3.5 minutes [SD]) before diving and a mean of 16.2 minutes (+/- 3.7 minutes [SD]) after diving. After centrifugation of microcapillaries, Ht was estimated on a visual plate reader. A paired Wilcoxon test showed evidence (P < .001) for a change in Ht. The mean difference between predive and postdive measurements was 0.0073 (95% confidence interval: 0.0104- 0.0042), equating to a mean relative Ht increase of 1.78%. Similar results were found for the sexes individually. A correlation between maximum depth of dive and Ht increase was statistically significant, although the correlation itself was weak (P = .049, Spearman's r = .326). There is evidence of a statistically significant increase in Ht over the course of a single warm-water scuba dive. This increase is small and is within the range of error associated with the techniques of Ht estimation employed in this study. Depth exposure was found to correlate with Ht increase. In view of the small magnitude of change in the Ht, there is no reason to amend protocols for fluid resuscitation of recreational scuba divers suspected to have experienced decompression injury in tropical locations.
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St Leger Dowse, M., Lee, V., Shaw, S., Smerdon, G.. Fife, C. and Bryson, P (2006) A relationship between the menstrual cycle and decompression illness: is the evidence building? Eur. J. Underwater. And Hyper. Med. 7(4):84-86
Summary: Controversy persists regarding any relationship between the menstrual cycle and decompression illness (DCI). Women now have greater involvement within the hypo and hyperbaric work place. Studies suggest a possible difference in risk of DCI, or problems during diving, over a typical 28 day cycle. We scrutinised the relevant published data from hypo and hyperbaric environments between the years 1988 to 2006. We also reviewed 250 records from a continued study involving 23 treatment chambers where women had been diagnosed and treated for DCI and for which the number of days between the first day of the last menstrual cycle and the problem dive was known. The 7 altitude and diving related abstracts and papers showed a relationship with DCI, or problems during diving, and the point in the menstrual cycle. Analysis of the 250 DCI treatment records also showed the incidence of DCI was not evenly distributed over the menstrual cycle, with more cases treated at the beginning and end of the typical 28 day cycle. The available evidence suggests there is a relationship between the risk of DCI, during hyperbaric or hypobaric exposure, or the occurrence of problems during hyperbaric exposure and the time in the menstrual cycle.
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Mills, C. & Bryson, P. (2006) The role of hyperbaric oxygen therapy in the treatment of sternal wound infection. Eur.J Cardiothorac.Surg. vol. 30, no. 1, pp. 153-159.
Summary: Sternal wound dehiscence and infection are major problems for patients and health care providers. A range of risk factors, including diabetes, obesity and internal thoracic artery harvest, has been implicated. Several pathophysiological mechanisms, which may account for the development of infection, have been proposed. There is a growing body of evidence which suggests that sternal ischaemia may play a significant role in the initiation of wound infection, and that this may be exacerbated by harvest of the internal thoracic artery. Current treatments for infection include wound debridement, irrigation and tissue flap reconstruction. In addition, several novel therapies such as negative pressure dressings have been shown to be safe and useful. Hyperbaric oxygen therapy - the administration of 100% oxygen at pressures greater than atmospheric pressure - is widely used in the treatment of various chronic wounds. The mechanism whereby hyperbaric oxygen exerts its effects is being elucidated and there is a growing body of clinical evidence that supports its use. It has been suggested that there may be a role for hyperbaric oxygen therapy in the treatment of sternal infection. The theoretical mechanisms would seem plausible, but at present there is only limited evidence to support its use. This review addresses the theory and evidence supporting the role of hyperbaric oxygen therapy in the treatment of sternal wound infection.
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St Leger Dowse, M., Gunby, A., Moncad, R., Fife, C., & Bryson, P. (2006) Scuba diving and pregnancy: can we determine safe limits? J Obstet. Gynaecol. vol. 26, no. 6, pp. 509-513.
Summary: 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 >90% 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.
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St Leger Dowse, M., Gunby, A., Phil, D., Moncad, R., Fife, C., Morsman, J., & Bryson, P. (2006) Problems associated with scuba diving are not evenly distributed across a menstrual cycle. J Obstet. Gynaecol. vol. 26, no. 3, pp. 216-221.
Summary: The problems encountered during scuba diving may be a contributing factor in an episode of decompression illness (DCI). Evidence exists that there may be a relationship between the position in the menstrual cycle and the occurrence of DCI. We examined, by prospective observation in female recreational scuba divers, any interaction between reported problems during diving (RPDD) and the position in the menstrual cycle. A total of 533 women, aged between 14 and 57 years, returned diaries for >6 months, with 61% returning diaries for 3 consecutive years. A total of 34,625 dives were reported within 11,461 menstrual cycles between 21 and 40 days in length, with 65% of women reporting at least one RPDD. Logistic regression showed a significant non-linear relationship between the position in the menstrual cycle and RPDD (p = 0.004). RPDD were not evenly distributed over the menstrual cycle; the rate per 1,000 dives varied from 39.2 at start of the cycle to 19.7 during week 3, and 31.9 in week 4. We concluded these field data suggest a possible correlation between the incidence of RPDD and the position in which they occurred in the menstrual cycle.
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Handy,R.D., Bryson,P., Moody,A.J., Handy,L.M. & Sneyd,J.R. (2005) Oxidative metabolism in platelets, platelet aggregation, and hematology in patients undergoing multiple hyperbaric oxygen exposures. Undersea Hyperb.Med. vol. 32, no 5, pp.327-340.
Summary: Repeated hyperbaric oxygen (HBO2) treatments at 2.2 ATA for 90 minutes each are used to treat chronically ill patients with problem wounds, but there are concerns about the cytotoxicity of oxygen to blood cells and platelet function during prolonged HBO2 therapy. We recruited 31 consenting patients scheduled for multiple HBO2 treatments to evaluate oxidative metabolism in platelets, platelet aggregation, and hematology (mean age +/- standard error, 61 +/- 2.6 years, 20 males, 11 females). Venous blood was collected before and after the 1st and 20th HBO2 treatments. No effect of HBO2 was observed on red cell counts, hematocrit, hemoglobin, mean red cell volume (MCV), platelet counts, basal levels of lactate production by platelets, ferric reducing ability of plasma (FRAP), or plasma protein. The capacity for oxidative metabolism (lactate ratio) in platelets was not affected by HBO2, except in smokers where it increased by the 20th HBO2 treatment. Mean lymphocyte count was increased by 38% after the 20th treatment. There was also a 23% increase in platelet protein content, and a 24% increase in arachidonic acid-dependent platelet activation. Collagen-dependent platelet aggregation was unaffected. Blood glucose showed HBO2-dependent variability, but remained in the normal range. Plasma lactate levels decreased significantly from 3.2 to 2.5 mmol/l by the end of the study. Overall, we found no evidence that 20 HBO2 sessions caused adverse effects on platelet aggregation or oxidative metabolism in platelets, red or white cell counts, or total antioxidant status of the plasma.
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Edge, C. J., St Leger Dowse, M., & Bryson, P. (2005) Scuba diving with diabetes mellitus - the UK experience 1991-2001 Undersea Hyperb.Med., vol. 32, no. 1, pp. 27-37.
Summary: The study surveyed the outcomes and practises of divers with diabetes mellitus. Diabetic persons wishing to learn to scuba-dive or established divers who had diabetes mellitus in the UK were requested to fill in a detailed questionnaire annually. Divers were asked to provide basic epidemiological information and general diving history. Data provided by the diver's diabetic physician provided independent evidence of the diver's medical status. These data were recorded and analysed. Data were gathered from 323 diabetic divers (269 male, 54 female) and 8,760 dives were recorded over 11 years. Two fatalities were reported, both in non-insulin dependent divers. One incident of hypoglycaemia underwater in an insulin dependent diabetic diver was reported. This survey showed that in the group of well-controlled diabetic divers studied, there were no serious problems due to hypoglycaemia when they dived. Long-term complications of diabetes must be excluded before a diabetic diver may be permitted to dive.
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Prior FGR , Gourlay T, Taylor KM, Bryson P, Hope SA, and Stroev P (2005) Filtration, pulse and permeability. An update on PulseReverse Osmosis. Filtration vol 1, no 2, pp113-128
Summary: PRO is an update to the Starling hypothesis of fluid exchange which incorporates permeability and pulsatility. It suggests that fluid balance occurs when the mean capillary pulse pressure (MCPP) is equal and opposite to the membrane osmotic pressure (MOP) down the length of the capillary. The pulse drives fluid exchange. The physico chemistry of osmosis, and research into the pulsatile nature of the capillary bed support the principals underlying PRO. PRO suggests that imbalance between MOP and MCPP results in either oedema, shock and hypertension. Preliminary clinical studies support these proposed mechanisms. PRO suggests that the shape of the pulse wave is critical to fluid exchange in order for the volume of fluid filtered out during systole to be equal and opposite to the volume reabsorbed during diastole. Arrhythmias and arterial stiffening both result in change in the pulse shape. Further research is required to investigate the impact of change in pulse shape on fluid exchange. PRO is a new model of fluid balance and exchange which offers a simple model for the development of oedema, shock and hypertension. It suggests that arrhythmias and arterial stiffening have a profound effect on fluid exchange. Further research is required to investigate the full implications of this hypothesis on the development and treatment of cardiac disease.
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Glanvill, P., St Leger Dowse, M., & Bryson, P. (2005) A longitudinal cohort study of UK divers with asthma:diving habits and asthma health issues. South Pacific Underwater Medicine Society (SPUMS J), vol. 35, no. 1, pp. 18-22.
Summary: Few epidemiological studies have evaluated the safety issues relating to diving and asthma. This study followed a group of divers for a period of up to five years, observing the effect of asthma on their normal diving habits. Certified divers were recruited. Data gathered included demographics, diving history, and asthma history. Divers returned data annually. Diving practices considered to expose a diver to an increased risk of arterial gas embolism were evaluated. One hundred divers participated (68 male, 32 female), 30 being new to the sport at the start of the study. There were 12,697 dives reported during the study, with 43 respondents improving their diving grade. Twenty-eight had performed a free ascent, 37 had shared air at some time in their diving career, and 15 had performed both exercises. It is unknown if these activities were routine diving practice or emergency procedures. Twenty reported problems during diving activities, with 12 reporting wheezing underwater. One respondent reported two episodes of decompression illness, and a patent foramen ovale was subsequently confirmed. All 20 respondents reporting problems would have been excluded from diving using the UK guidelines, together with a further 40 who reported specific trigger factors. This study suggests that current UK guidelines with regard to diving and asthma, in this study group, are sufficiently restrictive.
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Shaw, F. L., Handy, R. D., Bryson, P., Sneyd, J. R., & Moody, A. J. (2005) A single exposure to hyperbaric oxygen does not cause oxidative stress in isolated platelets: No effect on superoxide dismutase, catalase, or cellular ATP. Clin.Biochem., vol. 38, no. 8, pp. 722-726.
Summary: The aim of the study was to investigate whether a single hyperbaric oxygen exposure causes oxidative stress in isolated platelets. Isolated horse platelets were exposed to 100% oxygen at 2.2 atmospheres, or 100% oxygen under normobaric conditions, or air under normobaric conditions for 90 min. There were no differences in platelet SOD activity between conditions, but there was a rise in SOD in all cases after 24 h (in control platelets at 24 h, SOD was 11.9 +/- 1.9 nmol/min/mg protein compared to initial background levels of 8.2 +/- 1.9 nmol/min/mg protein) (P < 0.05). Neither platelet catalase activity nor platelet GSH concentration changed over time, nor between conditions (catalase activity remained at around 12 units/mg protein, and GSH at around 1.58 nmol/mg protein). These data suggest that a single HBO exposure has no detrimental effect on platelet biochemistry, and does not cause overt oxidative stress in vitro.
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St Leger Dowse, M., Barnes, R., Smerdon, G. R., & Bryson, P. (2005) Time to fly after hyperbaric treatment for decompression illness: current recommendations. SPUMS 35[2], 67-70.
Summary: 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.
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Hyams, A. F., Toynton, S. C., Jaramillo, M., Stone, L. R., & Bryson, P. J. (2004) Facial baroparesis secondary to middle-ear over-pressure: a rare complication of scuba diving. J. Laryngol. Otol. vol. 118, no. 9, pp. 721-723.
Summary: A facial nerve palsy, as a result of middle-ear high pressure, is a rare complication of sub-aqua diving. It may occur as a result of an acute pressure change in the middle ear during ascent in those patients who have experienced difficulty equalizing their middle-ear pressure during the prior descent. We present the case history of this occurring in a 21-year-old diver and discuss the pathophysiology, management and the previous literature. The correct diagnosis of this condition is important if unnecessary, and potentially hazardous, recompression treatment is to be avoided.
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Harding, S., Bryson, P. & Perfect, T. (2004) Investigating the relationship between simulated depth, cognitive function and metacognitive awareness. HSE Books. ISBN 0 7176 2884 1
Summary: This report describes a pilot study aimed at identifying the cognitive and metacognitive effects of simulated depth. The population studied were one hundred and three SCUBA divers recruited from the general diving population. The primary aim was to determine if people can tell when their performance is being affected by nitrogen narcosis. A secondary aim was to investigate demographic factors which may have affected an individual's ability to identify a change in their performance. Content: Summary; Introduction; Materials and methods; Deviations from protocol; Results; Discussion; Conclusions; References; Appendices; Acknowledgement. This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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St Leger Dowse, M., Gunby, A., Moncad, R., Fife, C., & Bryson, P. (2004) A prospective study of reverse dive profiles in UK female recreational divers. South Pacific Underwater Medicine Society (SPUMS J) vol. 34, no. 4, pp. 183-188.
Summary: Every-day diving habits of a large group of female recreational divers were observed for up to three years. Reverse dive profiles (RDPs) were compared with the conclusions of the Smithsonian Institution Reverse Dive Profiles Workshop. Volunteers did not know RDPs would be scrutinized, making changes to their diving habits unlikely. 570 participants returned "diaries"; 62% for three consecutive years, reporting 30,480 dive days (16,706 multiple dive days). The majority of dive depths ranged from 15m to 89m. In 29.7% of the multiple-dive days the second dives were a greater depth than the first dive, with 0.25% outside the Smithsonsian conclusions for RDP (depth differentials between the first and second dive of the day were >12m, and the 2nd dive was deeper than the 1st and deeper than 40m). Rates of self-assessed symptom data of possible decompression sickness (DCS) were analyzed by RDP with no significant correlation found (minimum p = 0.18). Maximum depth ever dived and total dives logged at the start of the study (surrogates for diving experience) are both significantly correlated with percentage of RDPs (p < 0.0001 and p 0.0008). There were significantly fewer RDPs for one dive training organization (p = 0.0005). This work suggests future studies should consider carefully the type and amount of data necessary to address these issues, with power calculations demonstrating 30,000 to 180,000 multiple dive days from 1,000 to 6,000 women needed for any significant effect (at the 5% level) to show. More complex physiologically based studies are possibly required.
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Lee, V., St Leger Dowse, M., Edge, C., Gunby, A., & Bryson, P. (2003) Decompression sickness in women: a possible relationship with the menstrual cycle. Aviat.Space Environ.Med. vol. 74, no.11, pp.1177-1182.
Summary: Women are increasingly participating in recreational scuba diving and the professional roles of women are expanding in the fields of aviation, space, and diving. Evidence exists that there may be a relationship between altitude decompression sickness (DCS) and the menstrual cycle, although diving studies to support such findings are limited. The aim of the present study was to investigate the presence of any relationship between the development of DCS in female sports divers, the phase of the menstrual cycle, and the use of the oral contraceptive pill (OCP). Personal, dive, symptom, and menstrual history details were collected by questionnaire from women treated with hyperbaric therapy for DCS in 23 treatment centers worldwide. There were 150 records suitable for analysis. The phase in the menstrual cycle of the DCS incident was estimated. The DCS incidents were unevenly distributed throughout the cycle (p = 0.001) with the greatest percentage of incidents occurring in the first week of the menstrual cycle. The variation in incidence across the cycle appeared to be greatest for the non-OCP users (p = 0.01), and when age was taken into account there was a significant difference between the OCP and non-OCP users with respect to risk of DCS across the menstrual cycle (p = 0.03). These data suggest that the risk of DCS may be dependent on the phase of the menstrual cycle and that the distribution of risk differs between OCP and non-OCP users.
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St Leger, D. M., Bryson, P., Gunby, A., & Fife, W. (2002) Comparative data from 2250 male and female sports divers: diving patterns and decompression sickness. Aviat. Space Environ. Med. vol. 73, no. 8, pp. 743-749.
Summary: The aim of the study was to compare the diving habits and histories of men and women in recreational scuba diving. More than 10,000 questionnaires were circulated to recreational divers in the United Kingdom. Retrospective, broad-based information was requested concerning general health, smoking, alcohol, recreational drug use, diving habits and histories, and physician-confirmed and self-diagnosed episodes of decompression sickness (DCS). Data relating only to women were also gathered. Questionnaires were anonymous. Over four years, 2250 divers responded, 47% of whom were women. Of the 458,827 dives reported, 310% were by women. Differences in diving habits were observed between men and women, which included number of dives per annum, maximum depths dived, and dives with extra stops. When the level of experience was taken into account in this study group, the estimated rate of DCS in men was 2.60 times greater than for women. In this study, comparison between men and women in recreational diving differed from the initial evaluation when underlying factors were taken into account. Future studies should attempt to control for underlying factors in the data gathering and data analysis.
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Cosgrove, H. & Bryson, P. (2001) Hyperbaric medicine in soft tissue trauma. Trauma, vol. 3, pp. 133-141.
Summary: Severe crush injuries of the soft tissues can result in tears of the large vessels and destruction of the microcirculation. This produces ischaemia and tissue necrosis and contributes to the development of oedema and compartment syndromes. All these factors compromise tissue survival. Immediately following a crush injury some areas of tissue are obviously irreversibly damaged and others undamaged. It is common to have a 'grey area' between these, where there is uncertainty as to what will survive. Management of crush injury must involve surgical repair of vessels and soft tissues, debridement of obviously dead tissue, and bone stabilization. At the same time tissue perfusion must be maintained by manoeuvres such as fluid replacement and diminution of oedema, and when necessary fasciotomy. It has been proposed that hyperbaric oxygen therapy has a role, as an adjunct, in the maintenance of tissue oxygenation under these conditions, and will improve survival of tissues in the grey area, and thus minimize tissue loss. Hyperbaric oxygen therapy involves breathing 100% oxygen at pressures greater than one atmosphere. Presently, the pressures most often used are in the range 2-3 atmospheres absolute.
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Wilmshurst, P. T., Pearson, M. J., Walsh, K. P., Morrison, W. L., & Bryson, P. (2001) Relationship between right-to-left shunts and cutaneous decompression illness. Clin.Sci.(Lond), vol. 100, no. 5, pp. 539-542.
Summary: The presence of a large right-to-left shunt is associated with neurological decompression illness after non-provocative dives, as a result of paradoxical gas embolism. A small number of observations suggest that cutaneous decompression illness is also associated with a right-to-left shunt, although an embolic aetiology of a diffuse rash is more difficult to explain. We performed a retrospective case--control comparison of the prevalence and sizes of right-to-left shunts determined by contrast echocardiography performed blind to history in 60 divers and one caisson worker with a history of cutaneous decompression illness, and 123 historical control divers. We found that 47 (77.0%) of the 61 cases with cutaneous decompression illness had a shunt, compared with 34 (27.6%) of 123 control divers [P[0.001]. The size of the shunts in the divers with cutaneous decompression illness was significantly greater than in the controls. Thus 30 (49.2%) of the 61 cases with cutaneous decompression illness had a large shunt at rest, compared with six (4.9%) of the 123 controls [P[0.001]. During closure procedures in 17 divers who had cutaneous decompression illness, the mean diameter of the foramen ovale was 10.9 mm. Cutaneous decompression illness occurred after dives that were provocative or deep in subjects without shunts, but after shallower and non-provocative dives in those with shunts. The latter individuals are at increased risk of neurological decompression illness. We conclude that cutaneous decompression illness has two pathophysiological mechanisms. It is usually associated with a large right-to-left shunt, when the mechanism is likely to be paradoxical gas embolism with peripheral amplification when bubble emboli invade tissues supersaturated with nitrogen. Cutaneous decompression illness can also occur in individuals without a shunt. In these subjects, the mechanism might be bubble emboli passing through an 'overloaded' lung filter or autochthonous bubble formation.
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Wilmshurst, P. & Bryson, P. (2000) Relationship between the clinical features of neurological decompression illness and its causes. Clin.Sci.(Lond), vol. 99, no. 1, pp. 65-75.
Summary: 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.
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Hunter, J. D., Roobottom, C. A., Bryson, P. J., & Brown, C. (1998) Conservative management of gastric rupture following scuba diving. J.Accid.Emerg.Med., vol. 15, no. 2, pp. 116-117.
Summary: Gastric rupture is an uncommon surgical problem which normally presents with an acute abdomen and peritonism. An unusual case following underwater ascent and its conservative management is presented.
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Edge, C. J., Grieve, A. P., Gibbons, N., O'Sullivan, F., & Bryson, P. (1997) Control of blood glucose in a group of diabetic scuba divers. Undersea Hyperb.Med., vol. 24, no. 3, pp. 201-207.
Summary: GA preliminary study to examine the hypothesis that the ability of well-controlled (defined as no hypoglycemic episodes within the last 12 mo., HbAlc < 9.0%, and none of the long-term complications of diabetes type I) diabetic scuba divers to control their serum glucose and dive without becoming hypoglycemic during a simulated dive to 27 meters of seawater in controlled environment is impaired. An open, controlled, crossover study compared blood glucose levels, hematocrits, and hematologic cell counts in a group of eight type I diabetic scuba divers to those from eight age- and sex-matched, normoglycemic control scuba divers. Each diver did one simulated dive and one control exercise on the surface on 2 consecutive days. The simulated dive was done to depth of 375 kPa in a hyperbaric chamber, the control exercise was done at ambient pressure. The order of the dive and the control exercise was randomized. No statistically significant differences were observed between serum glucose levels in the diabetic divers measured during the simulated dive to 375 kPa vs. the serum glucose levels in the diabetic divers measured during the control exercise at the same time points. All divers with type I diabetes remained free of symptoms and signs of hypoglycemia throughout the course of the trial, and no diabetic subject had a serum glucose less than 4 mmol/liter before the end of the trial. As the sample size was small, larger studies including subject with type II diabetes will be necessary to extend these results to the diabetic diving population at large. The authors conclude that, contrary to advice issued by most diving agencies to scuba divers, it may be safe to allow well-controlled subjects with type I diabetes with no long-term complications to undertake scuba diving, and that high partial pressures of oxygen do not seem to lower serum glucose levels significantly in the diabetic diver during the dive.
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Blanshard, J., Toma, A., Bryson, P., & Williamson, P. (1996) Middle ear barotrauma in patients undergoing hyperbaric oxygen therapy. Clin.Otolaryngol., vol. 21, no. 5, pp. 400-403.
Summary: Hyperbaric oxygen therapy is associated with a risk of barotrauma to the middle ear. This prospective study of 82 patients undergoing long-term therapy for chronic conditions was designed to measure the incidence and severity of middle ear barotrauma. Twenty-four patients (29.3%) required the insertion of ventilation tubes for otalgia, significantly more of whom were suffering from radionecrosis of the head and neck region (P < 0.01). Thirty-two of the remaining 58 patients (55%) underwent specialist ENT assessment by otoscopy and tympanometry. Five ears (8%) showed the otoscopic changes of barotrauma (TEED grade 3 or 4), and one ear (2%) showed tympanometric evidence of a middle ear effusion (Type B tympanogram). We conclude that despite careful tuition in pressure equalization and the appropriate use of ventilation tubes, up to 8% of ears sustain significant barotrauma. Tympanometry is unreliable in detecting these changes, otoscopy provides the most reliable screening technique.
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Edge, C. J., Grieve, A. P., Gibbins, N., O'Sullivan, F., & Bryson, P. (1996) Effects of pressure on whole blood glucose measurements using the Bayer Glucometer 4 blood glucose meter. Undersea Hyperb.Med., vol. 23, no. 4, pp. 221-224.
Summary: The effect of pressure was investigated on the readings of whole blood glucose obtained from the Bayer Glucometer 4 blood glucose meter which uses the hexokinase enzymatic reaction. Sixteen subjects (eight normal and eight insulin-dependent diabetics) were exercised in a hyperbaric chamber at a depth of 3.7 atm abs. Venous blood samples were monitored at regular intervals for whole blood glucose concentration as measured by a Glucometer 4 inside the chamber. The blood samples were immediately placed in an airlock and taken to 1 atm abs, where whole blood glucose concentrations were measured using an identical instrument. The remaining blood was then analyzed in duplicate for serum glucose concentration using standard laboratory methods. The results show a significant difference between whole blood glucose concentrations measured at pressure and those measured at atmospheric pressure. Significant differences are also observed between whole blood glucose concentrations measured under pressure and serum blood glucose concentrations measured at atmospheric pressure.
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Mason, M. J., Bryson, P., Cross, M., Todd, M., & Paul, V. (1996) Insertion of a permanent pacemaker in a professional diver. Eur.J.C.P.E., vol. 6, pp. 173-175.
Summary: Patients who require a permanent pacemaker are an increasingly diverse group and therefore the individual needs of the patient must be considered in detail. We report a female patient who has to dive on a regular basis as part of her profession and who required a permanent pacemaker for sinoatrial disease. To ensure that continued participation in diving would be appropriate, she undertook detailed assessment of her pacemaker function during a simulated "dry" dive in a hyperbaric chamber. After being taken to pressure equivalent to a depth of 50 metres, appropriate sensing and pacing behaviour was monitored whilst at rest, exercising on a static bicycle, and rocking to stimulate the accelerometer-driven rate response. This assessment was then repeated after returning to the "surface" to ensure that the pacemaker function remained intact. This case illustrates that care must be taken when choosing a pacemaker for an individual patient, but that having chosen appropriately it need not prohibit diving either as a recreational or professional activity.
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Morgan, M. S., Lytle, J., & Bryson, P. J. (1995) The place of hyperbaric oxygen in the treatment of gas gangrene. Br.J.Hosp.Med., vol. 53, no. 9, pp. 424-426.
Summary: Clostridial myonecrosis (gas gangrene) is fortunately only rarely encountered, so individual practitioners will inevitably have limited experience of its management. It is now over 30 years since Brummelkamp et al first described the beneficial effects of hyperbaric oxygen (HBO) therapy in the treatment of this life threatening condition (Brummelkamp et al, 1961). The very rapid progression of the condition necessitates speedy decision-making and the mobilisation of services which may be unfamiliar to the team managing the patient. However, it is still not widely appreciated that the rapid transfer of a critically ill patient to a centre providing facilities for the simultaneous provision of intensive care and HBO can not only be life-saving, but will improve the chances of successful treatment of the patient without major disabling surgery.
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Bryson, P., Edge, C., Lindsay, D., & Wilmshurst, P. (1994) The Case for Diving Diabetics. SPUMS J 24[1], 11-13.
Summary: To be allowed to dive the diabetic must not only satisfy medical criteria, but he or she must take additional precautions when diving, both to ensure the wellbeing of him/herself and also the wellbeing of the diving buddy and the rest of the party of divers. These conditions are set out in the following short review.
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Roobottom, C. A., Hunter, J. D., & Bryson, P. J. (1994) The diagnosis of fatal gas embolism: detection by plain film radiography. Clin.Radiol., vol. 49, no. 11, pp. 805-807.
Summary: Two recent deaths from massive air embolism occurring while scuba diving off the South coast of Britain are reported. In each case the circumstances of death were uncertain. In both instances the cause of death, that is massive gas embolism, was determined by plain radiography and findings were confirmed at post-mortem. These cases illustrate that in unexplained deaths that occur after exposure to, or change in hyper- or hypobaric conditions, investigation should include pain radiographs of the chest, abdomen and skull.
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