A retrospective review of divers treated for inner ear decompression sickness at Fiona Stanley Hospital hyperbaric medicine unit 2014-2020.

Introduction: Inner ear decompression sickness (IEDCS) is increasingly recognised in recreational diving, with the inner ear particularly vulnerable to decompression sickness in divers with a right-to-left shunt, such as is possible through a persistent (patent) foramen ovale (PFO). A review of patients treated for IEDCS at Fiona Stanley Hospital Hyperbaric Medicine Unit (FSH HMU) in Western Australia was performed to examine the epidemiology, risk factors for developing this condition, the treatment administered and the outcomes of this patient population. Methods: A retrospective review of all divers treated for IEDCS from the opening of the FSH HMU on 17 November 2014 to 31 December 2020 was performed. Patients were included if presenting with vestibular or cochlear dysfunction within 24 hours of surfacing from a dive, and excluded if demonstrating features of inner ear barotrauma. Results: There were a total of 23 IEDCS patients and 24 cases of IEDCS included for analysis, with 88% experiencing vestibular manifestations and 38% cochlear. Median dive time was 40 minutes and median maximum depth was 24.5 metres. The median time from surfacing to hyperbaric oxygen treatment (HBOT) was 22 hours. Vestibulocochlear symptoms fully resolved in 67% and complete symptom recovery was achieved in 58%. A PFO was found in 6 of 10 patients who subsequently underwent investigation with bubble contrast echocardiography upon follow-up. Conclusions: IEDCS occurred predominantly after non-technical repetitive air dives and ongoing symptoms and signs were often observed after HBOT. Appropriate follow-up is required given the high prevalence of PFO in these patients.

Effect of antiplatelet and/or anticoagulation medication on the risk of tympanic barotrauma in hyperbaric oxygen treatment patients, and development of a predictive model.

INTRODUCTION: Middle ear barotrauma (MEBt) is a common side effect of hyperbaric oxygen treatment (HBOT) and can result in pain, hearing loss, tinnitus and otorrhagia. The use of antiplatelet/anticoagulant drugs is thought to increase the risk and severity of MEBt during HBOT. METHODS: Single centre, retrospective observational cohort study of all patients treated with HBOT over a 4-year period (between 01 January 2015 to 31 December 2018) looking at the incidence of MEBt and the concurrent use of antiplatelet and/or anticoagulant drugs. MEBt was assessed by direct otoscopy of the tympanic membrane post-HBOT and scored using the modified Teed classification. Multivariate modelling assessed the relationship between antiplatelet and/or anticoagulation drug use, age, sex, and MEBt during HBOT. RESULTS: There was no evidence that antiplatelet and/or anticoagulation drugs increase the risk of tympanic barotrauma in HBOT patients. The prevalence of MEBt was higher in female patients than in males (χ2 P = 0.004), and increased with age (χ2 P = 0.048). No MEBt was recorded in patients undergoing recompression therapy for decompression sickness or cerebral arterial gas embolism. CONCLUSIONS: In this retrospective single-centre study, antiplatelet and/or anticoagulation drugs did not affect the risk of MEBt, but both age and sex did, with greater prevalence of MEBt among older patients and females compared with younger patients and males. A predictive model, requiring further validation, may be helpful in assessing the likelihood of MEBt in patients undergoing HBOT.

Association of microparticles and neutrophil activation with decompression sickness.

Decompression sickness (DCS) is a systemic disorder, assumed due to gas bubbles, but additional factors are likely to play a role. Circulating microparticles (MPs)--vesicular structures with diameters of 0.1-1.0 µm--have been implicated, but data in human divers have been lacking. We hypothesized that the number of blood-borne, Annexin V-positive MPs and neutrophil activation, assessed as surface MPO staining, would differ between self-contained underwater breathing-apparatus divers suffering from DCS vs. asymptomatic divers. Blood was analyzed from 280 divers who had been exposed to maximum depths from 7 to 105 meters; 185 were control/asymptomatic divers, and 90 were diagnosed with DCS. Elevations of MPs and neutrophil activation occurred in all divers but normalized within 24 h in those who were asymptomatic. MPs, bearing the following proteins: CD66b, CD41, CD31, CD142, CD235, and von Willebrand factor, were between 2.4- and 11.7-fold higher in blood from divers with DCS vs. asymptomatic divers, matched for time of sample acquisition, maximum diving depth, and breathing gas. Multiple logistic regression analysis documented significant associations (P < 0.001) between DCS and MPs and for neutrophil MPO staining. Effect estimates were not altered by gender, body mass index, use of nonsteroidal anti-inflammatory agents, or emergency oxygen treatment and were modestly influenced by divers' age, choice of breathing gas during diving, maximum diving depth, and whether repetitive diving had been performed. There were no significant associations between DCS and number of MPs without surface proteins listed above. We conclude that MP production and neutrophil activation exhibit strong associations with DCS.

Livedoid vasculopathy successfully treated with hyperbaric oxygen.

Livedoid vasculopathy is a painful, ulcerating condition of the lower legs, ankles and feet with the typical histological feature of hyalinising vascular change of dermal blood vessels with minimal inflammation. Therapeutic interventions have been diverse and varyingly successful. We report a biopsy-proven case in a 27-year-old male, which responded rapidly and completely to hyperbaric oxygen therapy. A few such cases have been reported previously, but only in dermatological journals, not in the hyperbaric medicine literature.

A double-blind, randomized trial of intravenous versus intramuscular antivenom for red-back spider envenoming.

OBJECTIVE: To compare the efficacy of intravenous versus intramuscular antivenom (AV) in the treatment of Red-back spider (RBS) envenoming. METHODS: Randomized, double-dummy, double-blind, multicentre trial of patients with red-back spider envenoming requiring AV treatment recruited from five hospital EDs in Western Australia. RESULTS: Thirty-five patients were recruited; two were excluded; 33 were available for initial analysis, but two who were unblinded after one ampoule of trial AV and given i.v. AV had limited data; 31 remained in the study and had more complete data. After AV, pain scores for both i.m. and i.v. groups improved rapidly. At 24 h, the i.v. group was better with a 55% absolute difference (76% vs. 21%; 95% CI 25-85% difference) in the proportion pain-free. There were no safety issues. CONCLUSIONS: Red-back spider antivenom was initially effective by both i.m. and i.v. routes. The study generates the hypothesis that at 24 h, significantly more patients are pain-free with i.v. administration. Definitive recommendations on the optimal route of administration of RBS AV await the results of further studies.