Emergency Medical Service Attendances for Adults with Repeat Falls in Western Australia: A State-Wide Retrospective Cohort Study.

OBJECTIVES: The risk of falls increases with age and often requires an emergency medical service (EMS) response. We compared the characteristics of patients attended by EMS in response to repeat falls within 30 days and 12 months of their first EMS-attended fall; and explored the number of days between the index fall and the subsequent fall(s). METHODS: This retrospective cohort study included all adults (> =18 years of age) who experienced their first EMS-attended fall between 1 January 2016 and 31 December 2020, followed up until 31 December 2021. Patients who experienced > =1 subsequent fall, following their first recorded fall, were defined as experiencing repeat falls. Multivariable logistic regression was used to identify the factors associated with repeat falls; and Kaplan-Meier analysis was used to estimate the time (in days) between consecutive EMS-attended falls. RESULTS: A total of 128,588 EMS-attended fall-related incidents occurred involving 77,087 individual patients. Most patients, 54,554 (71%) were attended only once for a fall-related incident (30,280 females; median age 73 years, inter-quartile range (IQR): 55-84). A total of 22,533 (29%) patients experienced repeat EMS-attended falls (13,248 females; median age 83 years, IQR: 74-89, at first call). These 22,533 patients accounted for 58% (74,034 attendances) of all EMS-attendances to fall-related incidents. Time between EMS-attended falls decreased significantly the more falls a patient sustained. Among the 22,533 patients who experienced repeat falls, 13,363 (59%) of repeat falls occurred within 12 months: 3,103 (14%) of patients sustained their second fall within 30 days of their index fall, and 10,260 (46%) between 31 days to 12 months. Patients who were transported to the hospital, via any urgency, at their first EMS-attended fall, had a reduced odds of sustaining a second EMS-attended fall within both 30 days and 31 days to 12 months, compared to non-transported patients. CONCLUSION: Nearly 30% of all patients attended by EMS for a fall, sustained repeat falls, which collectively accounted for nearly 60% of all EMS-attendances to fall-related incidents. Further exploration of the role EMS clinicians play in identifying and referring patients who sustain repeat falls into alternative pathways is needed.

Epidemiology and Severity of Medical Events for Mountain Bikers and Hikers Transported by Ambulance in Western Australia, 2015 to 2020.

INTRODUCTION: Outdoor activities offer physical and mental health benefits. However, incidents can occur requiring ambulance transport to hospital. This study aimed to describe the epidemiology and severity of traumatic and medical incidents for mountain bikers and hikers transported by ambulance within Western Australia. METHODS: This was a retrospective cohort study of ambulance-transported mountain bikers and hikers within Western Australia from 2015 to 2020. Data were extracted from ambulance electronic patient care records. Multivariable analyses were undertaken to identify variables associated with higher patient severity based on the National Early Warning Score 2 (NEWS2). RESULTS: A total of 610 patients required ambulance transport to hospital while mountain biking (n=329; 54%) or hiking (n = 281; 46%). Median age of mountain bikers and hikers was 38 (24-48) y and 49 (32-63) y, respectively. Paramedics reported a fracture in 92 (28%) mountain bikers and 78 (28%) hikers. The predominant injury locations for mountain bikers were upper limbs and for hikers, lower limbs. Cases were trauma related in 92% of mountain bikers and 55% of hikers. A significant association (P<0.001) between the etiology of the ambulance callout and patient severity was found. In trauma etiology cases, the frequency of medium-risk+ NEWS2 severity was 21.4%. In medical cases, the frequency of medium-risk+ severity was 40.8%. CONCLUSION: Both mountain bikers and hikers experienced incidents requiring ambulance transport to hospital. Incidents of a medical etiology had a higher clinical risk, as determined by the NEWS2 scores, regardless of activity being undertaken.

"Mind the gap": An exploratory qualitative study of paramedics' experiences attending older adults who fall in Western Australia.

PURPOSE: To explore paramedics' experiences and perspectives about attending and managing older adults who had fallen. PROCEDURES: This qualitative, exploratory study used a purposive sample of paramedics in Western Australia. Participants had at least one year of clinical experience. Semi-structured interviews were undertaken. Data were analysed via an inductive thematic approach. FINDINGS: Fourteen paramedics were interviewed (Median age: 38 years, n = 5 females). The main theme identified that experiences were positive when attending patients with high-acuity medical problems or injuries following falls because binary decision-making (transport vs non-transport) was appropriate. Themes highlighted that decision-making for low-acuity falls attendances was a complex balance between 1) patient context, 2) risk management, 3) paramedic reactions, and 4) the lack of alternate referral pathways available. Experiences could be stressful and frustrating when attending falls call-outs for older adults with no injuries or medical problems. Participants concurred that when transport to hospital was not required there were no available, alternative pathways to refer onwards for appropriate health or social care. CONCLUSION: Attending low-acuity call-outs for falls was often frustrating and required complex decision-making, with gaps in services identified. Further exploration of alternative referral pathways for health care for pre-hospital management of adults who fall is required.

Analgesic agents administered by ambulance personnel to mountain bikers and hikers on trails in Western Australia.

Objective: To describe the types of analgesic medications administered to patients who were attended by ambulance on recreational trails while mountain biking or hiking and report on the reduction in pain by these agents. Methods: This is a retrospective cohort study of patients attended by ambulance (2015-2021) after mountain biking or hiking, on Western Australia (WA) trails. All data were extracted from electronic patient care records created by ambulance personnel who attended the patient. We compared patient and case characteristics between mountain bikers and hikers and the reduction in pain scores achieved by different analgesics. Results: A total of 717 patients were included. Paramedics reported traumatic aetiology for mountain bikers in 92 % of cases and hikers in 58 % of cases. A pain score out of 10 was recorded for 538 (75 %) patients. The median (inter-quartile range) initial pain score was 6 (2-8) and the median final pain score was 3 (1-5). Around 48 % of these 538 patients reported ≥25 % reduction in their pain score. A reduction of ≥25 % in their pain score was greatest in those patients who received intravenous fentanyl (81 %), followed by patients administered multiple analgesics (72 %) and methoxyflurane only (52 %). Even 37 % of 134 patients who received no analgesia still reported ≥25 % reduction in their pain score by hospital arrival. Conclusion: Trauma was the most common reason mountain bikers and hikers on trails called an ambulance and a large proportion of these patients were in pain on ambulance arrival. Further work assessing the effectiveness of safe, non-opioid analgesics, additional to methoxyflurane, is needed to ensure non-registered practitioners such as first aid providers and event medical teams can offer suitable safe analgesics to these patients. Additionally, among patients given no pharmacological analgesic agent, almost half still achieved a >25 % reduction in their pain scores which reiterates the importance of non-pharmacological pain reduction strategies.

Epidemiology of ambulance-attended adults who fell in Western Australia 2015 - 2021: An increasing incidence in an ageing population.

BACKGROUND: Emergency Medical Services (EMS) are attending an increasing number of adults who fall. This study aimed to describe the incidence, patient characteristics, treatments and disposition of ambulance attended patients who fell in Western Australia (WA). METHODS: An ordinal logistic regression (using STATA) was conducted in this retrospective cohort study, analysing predictors of lower compared to higher transport urgency levels. Participants were adults ( ≥ 18 years) who fell and required ambulance attendance in WA between 1st January 2015 - 31st December 2021. RESULTS: A total of 188,720 patients (female = 107,811, 57 %) were attended by ambulances after falls, (median age = 80 years [IQR 67-87]). The age-standardized incidence rate of ambulance attended falls increased from 115 cases/100,000 person-years to 161 cases/100,000 person-years between 2015 and 2021. A total of 89,140 (47 %) patients had an injury recorded by paramedics, most often lacerations or suspected fractures. The electronic patient care record showed, 50,044 (26.5 %) patients received medication and 30,954 (16.4 %) patients received other intervention, e.g., ECG. A total of 148,050 (78 %) patients were transported to hospital with the following urgency levels: 2,371 (2 %) via urgency one; 27,882 (19 %) via urgency two, 93,447 (63 %) via urgency three and 22,584 (15 %) via urgency four and five ( < 1 % unknown urgency). Positive predictors of lower level transport urgency to hospital included being female and older than 65 years of age. CONCLUSION: Older, female patients had higher odds of being transported via a lower urgency, with 50 % of this cohort transported via urgency three. While 19 % of patients were attended via a Priority one, only 1 % were transported to hospital via urgency one. The incidence rate of falls requiring ambulance attendance has increased over time, increasing the demand placed on EMS annually.

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.

Types and anatomical locations of injuries among mountain bikers and hikers: A systematic review.

BACKGROUND: Mountain biking and hiking continue to grow in popularity. With new participants to these sports, it is likely the number of injuries will increase. To assist medical personnel in the management of these patients we attempted to quantify the types and locations of injuries sustained by mountain bikers and hikers. Objective The objective of this systematic review is to identify the type and anatomical location of injuries for both mountain bikers and hikers. METHODS: A systematic search was undertaken using CINAHL, Cochrane, ProQuest, PubMed and Scopus databases. Reviewers assessed the eligibility of articles by a title/abstract review and final full-text review. Studies were included if the types of injuries were reported by medical personnel and contained anatomical locations. Studies were excluded if it did not take place on a trail or if the injuries were self-reported. Risk of bias was assessed utilising the Joanna Briggs Institute (JBI) checklists for study quality. No meta-analysis or comparison between mountain bikers and hikers was possible due to the high heterogeneity of the definition of injury. RESULTS: A total of 24 studies met the inclusion criteria, 17 covering mountain biking and 7 hiking. This represented 220,935 injured mountain bikers and 17,757 injured hikers. The most common type of injuries sustained by mountain bikers included contusions, abrasions and minor lacerations, which made up between 45-74% of reported injuries in studies on competitive racing and 8-67% in non-competitive studies. Fractures represented between 1.5-43% of all reported injuries. The most injured region was the upper limbs reported in 10 of 17 studies. For hikers the most common injuries included blisters and ankle sprains with blisters representing 8-33% of all reported injuries. The most common body location to be injured by hikers was a lower limb in all 7 studies. CONCLUSIONS: This is the first systematic review to report on the injury epidemiology of the two most common trail users; mountain bikers and hikers. For participants in both activities the majority of injuries were of minor severity. Despite this, the high proportions of upper limb fractures in mountain bikers and ankle sprains in hikers cannot be ignored. TRIAL REGISTRATION: Registration: This systematic review was prospectively registered with the University of York PROSPERO database on the 12/4/2021 (CRD42021229623) https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021229623.

The prehospital management of ambulance-attended adults who fell: A scoping review.

BACKGROUND: The ageing population is requiring more ambulance attendances for falls. This scoping review aimed to map and synthesise the evidence for the prehospital management of Emergency Medical Services (EMS) attended adult patients who fall. METHODS: The Joanna Briggs Institute methods for scoping reviews were used. Six databases were searched (Medline, Scopus, CINAHL, Cochrane, EMBASE, ProQuest), 1st August 2021. Included sources reported: ambulance attended (context), adults who fell (population), injuries, interventions or disposition data (concept). Data were narratively synthesised. RESULTS: One-hundred and fifteen research sources met the inclusion criteria. Detailed information describing prehospital delivered EMS interventions, transport decisions and alternative care pathways was limited. Overall, adults< 65 years were less likely than older adults to be attended repeatedly and/or not transported. Being male, falling from height and sustaining severe injuries were associated with transport to major trauma centres. Older females, falling from standing/low height with minor injuries were less likely to be transported to major trauma centres. CONCLUSION: The relationship between patient characteristics, falls and resulting injuries were well described in the literature. Other evidence about EMS management in prehospital settings was limited. Further research regarding prehospital interventions, transport decisions and alternative care pathways in the prehospital setting is recommended.

Hyperbaric exposure in rodents with non-invasive imaging assessment of decompression bubbles: A scoping review protocol.

Hyperbaric pressure experiments have provided researchers with valuable insights into the effects of pressure changes, using various species as subjects. Notably, extensive work has been done to observe rodents subjected to hyperbaric pressure, with differing imaging modalities used as an analytical tool. Decompression puts subjects at a greater risk for injury, which often justifies conducting such experiments using animal models. Therefore, it is important to provide a broad view of previously utilized methods for decompression research to describe imaging tools available for researchers to conduct rodent decompression experiments, to prevent duplicate experimentation, and to identify significant gaps in the literature for future researchers. Through a scoping review of published literature, we will provide an overview of decompression bubble information collected from rodent experiments using various non-invasive methods of ultrasound for decompression bubble assessment. This review will adhere to methods outlined by the Joanna Briggs Institute Manual for Evidence Synthesis and be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR). Literature will be obtained from the PubMed, Embase, and Scopus databases. Extracted sources will first be sorted to a list for inclusion based on title and abstract. Two independent researchers will then conduct full-text screening to further refine included papers to those relevant to the scope. The final review manuscript will cover methods, data, and findings for each included publication relevant to non-invasive in vivo bubble imaging.

Baroreflex sensitivity derived from the Valsalva manoeuvre: A physiological protective factor for anxiety induced by breathing CO2-enriched air.

This study aimed to determine the capacity of baroreflex sensitivity, derived from the Valsalva manoeuvre (BRS_v), to predict state anxiety induced by a biological stressor (CO2 inhalation). Healthy adults (n = 50) breathed 7.5 % CO2-enriched air for 8 min, preceded and followed by breathing medical air for 5 min. State anxiety was evaluated with a visual analogue scale. Anxiety sensitivity (Anxiety Sensitivity Index-3; ASI-3) and trait anxiety (Trait form of the State-Trait Anxiety Inventory; STAI_T) served as cognitive-affective predictors. BRS_v was adopted as a physiological predictor. Multiple regression analysis revealed that BRS_v predicted lower anxiety during CO2 exposure, and attenuated the effect of ASI-3 in increasing anxiety. No significant effects were found for STAI_T. This is the first study to identify baroreflex sensitivity as a strong protective physiological factor for anxiety beyond the effect of anxiety sensitivity.

A survey of caustic cocktail events in rebreather divers.

INTRODUCTION: Closed-circuit rebreathers (CCRs) are designed to be watertight. Ingressing water may react with carbon dioxide absorbent in the CCR, which may produce alkaline soda with a pH of 12-14, popularly referred to by CCR divers as a 'caustic cocktail'. This study aimed to explore divers' responses to caustic cocktail events and to investigate if CCR diving experience is associated with experiencing a caustic cocktail. METHODS: An online survey instrument was developed and an invitation to participate was extended to certified CCR divers aged ≥ 18 years. Relationships between number of caustic cocktail events and potential risk factors: age; hours of rebreather diving experience; and number of rebreather dives were explored. RESULTS: Of the 413 respondents, 394 (95%) identified as male, mean age was 46 years and median length of CCR certification was six years. Fifty-seven percent (n = 237) of respondents reported having experienced a caustic cocktail. The probability of self-reporting none, one, or more caustic cocktail events increased with experience. Divers reported a variety of first aid treatments for caustic cocktails, with ∼80% citing their CCR instructor as a source of information. CONCLUSIONS: The more hours or dives a CCR diver accrues, the more likely they will self-report having experienced one or more caustic cocktail events. The majority of CCR divers responded to a caustic cocktail by rinsing the oral cavity with water. A proportion of divers, however, responded by ingesting soda, dairy, juice, or a mildly acidic solution such as a mixture of vinegar and water. The recommendation to immediately flush with water needs reinforcing among rebreather divers.

Health and wellbeing of recently active United States scuba divers.

INTRODUCTION: This study aimed to describe recently active adult scuba divers in the United States (US) and compare their characteristics with other active adults. The research question was: do active scuba divers have different health and wellbeing characteristics, compared with adults active in other pursuits? METHODS: The Behavioural Risk Factor Surveillance System (BRFSS) is a proportionally representative annual survey of adults in the US. It is the largest continuous population health survey in the world. Since 2011, data on scuba diving is collected biannually. A comparison group were matched on age, sex, being physically active and state of residence. RESULTS: The dataset comprised 103,686,087 person-years of monthly behavioural data, including 14,360 person years of monthly scuba data. The median weekly frequency of recent scuba diving was 1.0 times per week and the median weekly duration was equivalent to two dives each of one hour. Compared with the comparison group, divers more often earned > USD$50,000 per year, were less frequently married, with fewer children in the house, which they more often owned. They reported being able to afford a doctor if needed within the previous year, but more often reported excellent/good health and excellent/good mental health, despite the divers being 16% more frequently overweight. CONCLUSIONS: The results demonstrate a relatively healthy cohort of active scuba divers, confirming previous survey results that active divers are commonly college-educated, unmarried, without children, home owning, often overweight, they often currently drink alcohol, and smoked tobacco in the past, but commonly gave up smoking ten years or more ago.

Prognostic indicators for naïve canine non-indolent T-cell lymphoma treated with combination lomustine, vincristine, procarbazine and prednisolone chemotherapy.

Lomustine, vincristine, procarbazine and prednisolone (LOPP) chemotherapy has been suggested to be an effective treatment for dogs with naïve non-indolent T-cell lymphoma (TCL). Studies evaluating prognostic factors for dogs with TCL treated with LOPP chemotherapy are lacking. The aim of this retrospective study was to assess potential prognostic factors for canine naïve non-indolent TCL treated with the LOPP protocol. This was a retrospective cohort study of naïve non-indolent TCL treated with the LOPP chemotherapy protocol at a single specialty veterinary oncology clinic. Sixty-seven dogs met the inclusion criteria. The outcomes assessed included progression free survival (PFS), overall survival time (OST) and duration of complete response (DCR). The overall median PFS was 118 days (range 7-2302 days). The median OST was 202 days (range 8-2302 days). The overall median DCR was 316 days (range 38-2261 days). Number of treatments administered (p < .0001), multicentric disease (p = .044) and the presence of hypercalcaemia (p = .006) were prognostic indicators for PFS. Increasing number of treatments (p < .0001) and age (p = .0088) were prognostic indicators for OST. To our knowledge, this is the first study to describe hypercalcaemia as a positive prognostic indicator of PFS for TCL treated with LOPP chemotherapy. LOPP chemotherapy can be considered as a first-line treatment protocol against naïve hypercalcaemic non-indolent TCL.

Racial/ethnic distribution of graduates from doctorate and masters epidemiology degree programs in the United States, 2008 to 2018.

PURPOSE: To identify trends in racial and ethnic diversity of epidemiology graduate degree recipients in the United States between academic years 2008 and 2018. METHODS: National-level data from the National Center for Education Statistics was analyzed to assess the change in proportions of epidemiology degrees conferred to each racial/ethnic group - American Indian or Alaska Native; Asian, Native Hawaiian or Other Pacific Islander; Black or African American; Hispanic or Latino; White; and two or more races- over two time periods, Fall 2007- Spring 2012 (Period 1) and Fall 2012 - Spring 2018 (Period 2). RESULTS: During Period 13,837 epidemiology graduate degrees were conferred, and 6960 in Period 2. Within race/ethnicity groups, there was a statistically significant increase in graduate epidemiology degrees awarded over the two time periods to students of Hispanic or Latino ethnicity, and to students reporting two or more races. The proportion of degrees awarded to non-White students in aggregate increased by 4.7 percentage points, from 33.5% to 38.2%, while awards to White students decreased by the same amount. CONCLUSIONS: Overall, the racial/ethnic diversity of epidemiology graduates in the United States increased between 2008 and 2018, however, further efforts are needed to increase awards within some racial minority subgroups.

Machine learning and natural language processing to identify falls in electronic patient care records from ambulance attendances.

We derived machine learning models utilizing features generated by natural language processing (NLP) of free-text data from an ambulance services provider to identify fall cases. The data comprised samples of electronic patient care records care records (ePCRs) from St John Western Australia (WA), the sole ambulance services provider in most of WA. We manually labeled fall cases by reviewing the free-text summary. The models used features including case characteristics (e.g., age) and text frequency-inverse document frequency (tf-idf) of each word of the free-text generated by NLP. Support vector machine (SVM) and random forest were used as classifiers. We compared the performance of the models against the manual identification of falls by recall, precision, and F-measure. A total of 9,447 cases (1%) were randomly sampled, of which 1,648 (17%) were labeled as fall. The best model was an SVM model using case characteristics and tf-idf's of the first 100 words of free-text, with recall of 0.84, precision of 0.86, and F-measure of 0.85. This performance was better than an SVM model with only case characteristics. Machine-learning models incorporated with features generated by NLP improved the performance of classifying fall cases compared with models without such features. Scope remains for further improvement.

Mortality rate during professionally guided scuba diving experiences for uncertified divers, 1992-2019.

INTRODUCTION: The aim of this study was to re-examine the mortality rate among participants in the Professional Association of Diving Instructors' (PADI)'s Discover Scuba Diving (DSD) programme. METHODS: Fatalities reported to PADI as having occurred during DSD scuba dives were counted for each year between 1992 and 2019. DSD participant registrations were also counted for each year. The data were conveniently divided into two equal 14-year periods, 1992-2005 ('early') and 2006-2019 ('late'). To smooth out the year-to-year variation in raw rates, Monte Carlo simulations were performed on the mean rate per 100,000 participants per year during each period. RESULTS: There were a total of 7,118,731 DSD participant registrations and 79 fatalities during the study period. The estimated overall mean mortality rate in the early period was 2.55 per 100,000 DSD registrations whereas the estimated rate of 0.87 per 100,000 DSD registrations was significantly lower in the late period (P < 0.0001). CONCLUSIONS: PADI's contemporary Discover Scuba Diving introductory scuba experiences, at 0.87 fatalities per 100,000 participants, have a calculated mortality rate that is less than half that calculated for 1992-2008. The late period's rate improvement appears due either to significant under-registration in the early period, or to significant safety-performance improvement in the late period or, more likely, some combination of the two.

Incidence of cardiac arrhythmias and left ventricular hypertrophy in recreational scuba divers.

INTRODUCTION: The aims of this study were to investigate the potential impact of age, sex and body mass index (BMI) upon the incidence of arrhythmias pre- and post- diving, and to identify the prevalence of left ventricular hypertrophy (LVH) in older recreational divers. METHODS: Divers aged ≥ 40 years participating in group dive trips had ECG rhythm and echocardiograph recordings before and after diving. Arrhythmias were confirmed by an experienced human reader. LVH was identified by two-dimensional echocardiography. Weighted (0.5 fractional) values were used to account for participation by seven divers in 14 trips. RESULTS: Seventy-seven divers undertook 84 dive trips and recorded 677 dives. Among divers with no pre-trip arrhythmias (n = 55), we observed that 6.5 (12%) recorded post-trip arrhythmias and the median increase was 1.0 arrhythmia. In divers with pre-trip arrhythmias, 14.5 had a median of 1.0 fewer post-trip arrhythmias, 2.0 had no change and 5.5 had a median of 16.0 greater. Age, but neither sex nor BMI, was associated with change in the number of arrhythmias before and after dive trips (P = 0.02). The relative risk for experiencing a change in the frequency of arrhythmias after a diver trip, was 2.1 for each additional 10 years of age (95% CI 1.1, 4.0). Of the 60 divers with imaging of their heart, five had left ventricular hypertrophy. CONCLUSIONS: We observed a higher than expected prevalence of arrhythmias. Divers with pre-trip arrhythmias tended to be older than divers without pre-trip arrhythmias (P = 0.02). The prevalence of LVH in our cohort was one quarter of that found post-mortem in scuba fatalities.

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.

Physiological characteristics associated with increased resistance to decompression sickness in male and female rats.

Decompression sickness (DCS) is a complex and poorly understood systemic disease with wide interindividual resistance variability. We selectively bred rats with a threefold greater resistance to DCS than standard ones. To investigate possible physiological mechanisms underlying the resistance to DCS, including sex-related differences in these mechanisms, 15 males and 15 females resistant to DCS were compared with aged-matched standard Wistar males (n = 15) and females (n = 15). None of these individuals had been previously exposed to hyperbaric treatment. Comparison of the allelic frequencies of single nucleotide polymorphisms (SNPs) showed a difference of one SNP located on the X chromosome. Compared with nonresistant rats, the neutrophil-to-lymphocyte ratio and the plasmatic activity of coagulation factor X were significantly higher in DCS-resistant individuals regardless of their sex. The maximal relaxation elicited by sodium nitroprusside was lower in DCS-resistant individuals regardless of their sex. Males but not females resistant to DCS exhibited higher neutrophil and lymphocyte counts and higher prothrombin time but lower mitochondrial basal O2 consumption and citrate synthase activity. Principal components analysis showed that two principal components discriminate the DCS-resistant males but not females from the nonresistant ones. These components were loaded with activated partial thromboplastin time, monocyte-to-lymphocyte ratio, prothrombin time, factor X, and fibrinogen for PC1 and red blood cells count and neutrophils count for PC2. In conclusion, the mechanisms that drive the resistance to DCS appear different between males and females; lower coagulation tendency and enhanced inflammatory response to decompression stress might be key for resistance in males. The involvement of these physiological adaptations in resistance to DCS must now be confirmed.NEW & NOTEWORTHY By selective breeding of individuals resistant to decompression sickness (DCS) we previously obtained a rat model of inherited resistance to this pathology. Comparison of these individuals with nonresistant animals revealed differences in leukocyte counts, coagulation, and mitochondrial and vascular functions, but not resistance to oxidative stress. This study also reveals sex-related differences in the physiological changes associated with DCS resistance. A principal components analysis of our data allowed us to discriminate DCS-resistant males from standard ones, but not females. These differences represent possible mechanisms driving resistance to DCS. Although still far from the diver, this opens a pathway to future adaptation of personalized decompression procedures for "DCS-prone" individuals.

Simulated air dives induce superoxide, nitric oxide, peroxynitrite, and Ca2+ alterations in endothelial cells.

Human diving is known to induce endothelial dysfunction. The aim of this study was to decipher the mechanism of ROS production during diving through the measure of mitochondrial calcium concentration, peroxynitrite, NO°, and superoxide towards better understanding of dive-induced endothelial dysfunction. Air diving simulation using bovine arterial endothelial cells (compression rate 101 kPa/min to 808 kPa, time at depth 45 min) was performed in a system allowing real-time fluorescent measurement. During compression, the cells showed increased mitochondrial superoxide, peroxynitrite, and mitochondrial calcium, and decreased NO° concentration. MnTBAP (peroxynitrite scavenger) suppressed superoxide, recovered NO° production and promoted stronger calcium influx. Superoxide and peroxynitrite were inhibited by L-NIO (eNOS inhibitor), but were further increased by spermine-NONOate (NO° donor). L-NIO induced stronger calcium influx than spermine-NONOate or simple diving. The superoxide and peroxynitrite were also inhibited by ruthenium red (blocker of mitochondrial Ca2+ uniporter), but were increased by CGP (an inhibitor of mitochondrial Na+-Ca2+ exchange). Reactive oxygen and nitrogen species changes are associated, together with calcium mitochondrial storage, with endothelial cell dysfunction during simulated diving. Peroxynitrite is involved in NO° loss, possibly through the attenuation of eNOS and by increasing superoxide which combines with NO° and forms more peroxynitrite. In the field of diving physiology, this study is the first to unveil a part of the cellular mechanisms of ROS production during diving and confirms that diving-induced loss of NO° is linked to superoxide and peroxynitrite.