Variability in venous gas emboli following the same dive at 3,658 meters.

Exposure to a reduction in ambient pressure such as in high-altitude climbing, flying in aircrafts, and decompression from underwater diving results in circulating vascular gas bubbles (i.e., venous gas emboli [VGE]). Incidence and severity of VGE, in part, can objectively quantify decompression stress and risk of decompression sickness (DCS) which is typically mitigated by adherence to decompression schedules. However, dives conducted at altitude challenge recommendations for decompression schedules which are limited to exposures of 10,000 feet in the U.S. Navy Diving Manual (Rev. 7). Therefore, in an ancillary analysis within a larger study, we assessed the evolution of VGE for two hours post-dive using echocardiography following simulated altitude dives at 12,000 feet. Ten divers completed two dives to 66 fsw (equivalent to 110 fsw at sea level by the Cross correction method) for 30 minutes in a hyperbaric chamber. All dives were completed following a 60-minute exposure at 12,000 feet. Following the dive, the chamber was decompressed back to altitude for two hours. Echocardiograph measurements were performed every 20 minutes post-dive. Bubbles were counted and graded using the Germonpré and Eftedal and Brubakk method, respectively. No diver presented with symptoms of DCS following the dive or two hours post-dive at altitude. Despite inter- and intra-diver variability of VGE grade following the dives, the majority (11/20 dives) presented a peak VGE Grade 0, three VGE Grade 1, one VGE Grade 2, four VGE Grade 3, and one VGE Grade 4. Using the Cross correction method for a 66-fsw dive at 12,000 feet of altitude resulted in a relatively low decompression stress and no cases of DCS.

Understanding dive behavior of artisanal fishermen divers of the Yucatán Peninsula.

INTRODUCTION/BACKGROUND: Artisanal fishermen dive for sustenance. The lifetime prevalence of decompression sickness (DCS) in this population is alarmingly high. We wanted to understand the level of decompression stress fishermen in this region of the Yucatán experience in their daily fishing effort. We used a mathematical model to quantify nitrogen-loading in a nine-tissue compartment model. MATERIALS AND METHODS: Approved by the UCLA IRB 2 #13-000532, this study was conducted during fishing seasons 2012 through 2017. Diving fishermen were instructed to attach dive recorders to their waists every fishing day during the study period. Sensus Ultra dive recorders (ReefNet Inc.), with an accuracy of ±1 foot of seawater (fsw), 0.304 meters, and an activation depth of 10 fsw, 3.04 meters, were used to record dive parameters. Sampling interval was set to 10 seconds. A program in RStudio was created to extract the dive profiles of each fishing day and curtail into single-line outputs: pressure, time, date, start of dive and end of dive. An exponential decay formula was used to calculate the nitrogen-loading pressures for nine theoretical tissue compartments. Final nitrogen pressure, controlling compartments, decompression stop and time at stop were calculated. RESULTS: Fishermen completed 4,961 dives over 1,758 diving days during the study period. The 40-minute compartment controlled most of the dives. The 80-minute compartment controlled 5%-20% of dives two through five. Decompression stop times for the last dive ranged from one minute to 190 minutes. Most of the required stop time observed was seen at depths of 1-15 fsw.

Decompressing rescue personnel during Australian submarine rescue operations.

INTRODUCTION: Personnel rescuing survivors from a pressurized, distressed Royal Australian Navy (RAN) submarine may themselves accumulate a decompression obligation, which may exceed the bottom time limits of the Defense and Civil Institute of Environmental Medicine (DCIEM) Air and In-Water Oxygen Decompression tables (DCIEM Table 1 and 2) presently used by the RAN. This study compared DCIEM Table 2 with alternative decompression tables with longer bottom times: United States Navy XVALSS_DISSUB 7, VVAL-18M and Royal Navy 14 Modified tables. METHODS: Estimated probability of decompression sickness (PDCS), the units pulmonary oxygen toxicity dose (UPTD), the volume of oxygen required and the total decompression time were calculated for hypothetical single and repetitive exposures to 253 kPa air pressure for various bottom times and prescribed decompression schedules. RESULTS: Compared to DCIEM Table 2, XVALSS_DISSUB 7 single and repetitive schedules had lower estimated PDCS, which came at the cost of longer oxygen decompressions. For single exposures, DCIEM schedules had PDCS estimates ranging from 1.8% to 6.4% with 0 to 101 UPTD and XVALSS_DISSUB 7 schedules had PDCS of less than 3.1%, with 36 to 350 UPTD. CONCLUSIONS: The XVALSS_DISSUB 7 table was specifically designed for submarine rescue and, unlike DCIEM Table 2, has schedules for the estimated maximum required bottom times at 253 kPa. Adopting these tables may negate the requirement for saturation decompression of rescue personnel exceeding DCIEM limits.

Turkish recreational divers: a comparative study of their demographics, diving habits, health and attitudes towards safety.

INTRODUCTION: In Turkey, scuba diving has become more popular and accessible in the past decade and there has been a commensurate rise in the number of certified divers. This new generation of recreational divers has not been described in detail previously. The aim of this study was to profile this group, while investigating any gender differences and making comparisons with the global diving community. METHODS: Turkish dive club members and diving forum/blog readers were invited to complete an online questionnaire investigating their demography, medical issues and diving history and habits. RESULTS: The questionnaire was completed by 303 female and 363 male divers. Significant differences were found between the sexes in terms of demographics, diving experience and attitudes toward safety. Previous or ongoing medical conditions were reported by 100 female divers and 141 males. Only 29% of females and 22% of males had been examined by a physician trained to conduct assessments of fitness to dive. Female divers did not report problems while diving during menstruation or while taking oral contraceptives. There was no significant difference in the occurrence of decompression sickness (DCS) and DCS-like symptoms between the sexes. CONCLUSION: This is the largest study to date conducted on recreational divers in Turkey and so carries some value. It profiles their physical and behavioral attributes as well as differences in diving practices between the sexes in Turkey. Our findings should have implications for medical screening and dive training standards.

Influência de parâmetros clínicos, radiográficos, cirúrgicos e histopatológicos na taxa de recidiva dos ceratocistos odontogênicos: uma análise retrospectiva de coorte / Influence of clinical-radiographic, surgical and histopathological parameters in recurrence rate of Odontogenic Keratocysts: a retrospective cohort analysis

Não existe, na literatura, um consenso sobre o protocolo ideal de tratamento do Ceratocisto Odontogênico (CO). Isso se deve a alguns fatores, dentre eles à falta de padronização adequada dos dados avaliados nos trabalhos científicos. Essa falha é, muitas vezes, inerente a estudos retrospectivos. O objetivo deste estudo é avaliar a influência de parâmetros clínicos, radiográficos, cirúrgicos e histopatológicos no índice de recidiva do CO. Como diferencial, foram selecionados casos tratados de maneira uniforme e detalhada, pelo mesmo cirurgião. O tratamento foi a enucleação associada à ostectomia periférica, precedida ou não por descompressão da lesão. A amostra (n=24) foi composta por pacientes, com uma média de idade de 32.1 anos, que se apresentaram para tratamento inicial de uma lesão única de CO. Quatorze lesões (58.4%) foram submetidas a descompressão prévia. O tempo médio de acompanhamento dos pacientes foi de 60.5 meses (DP=31.3). Oito indivíduos (33%) apresentaram recidiva dos Cos e o tempo médio para desenvolvimento da recidiva foi de 19 meses (DP=4.9). Todas as recidivas foram diagnosticadas nos dois primeiros anos de acompanhamento e estavam significativamente associadas com: 1) pobre resposta clínica à descompressão (p=0.027); 2) preservação de dentes com evidência radiográfica de envolvimento de lesão entre as raízes dentárias (p=0.009) e 3) presença de brotamento epitelial da camada basal com ou sem formação de ilhas epiteliais na cápsula fibrosa (p=0.019). Este estudo sugere que parâmetros clínicos, radiográficos e microscópicos podem influenciar a recidiva do CO e têm a possibilidade ser avaliados individualmente como guia terapêutico

There is no consensus, in the literature, regarding the best protocol of treatment of Odontogenic Keratocyst (OKC). This is due to several factors, including the lack of adequate standardization of data assessed in the studies. This failure is usually inherent to retrospective studies. The objective of this study is to evaluate the influence of clinical, radiographic, surgical and microscopic parameters in the relapse rate of the disease. The differential aspect is in the uniform and detailed treatment applied by the same surgeon in all cases. The treatment applied was the enucleation with peripheral ostectomy, preceded by lesion decompression or not. The sample (n=24) was composed of patients, with a mean age of 32.1 years, presenting for the management of one untreated OKCs. Fourteen lesions (58.4%) were submitted to previous decompression procedure. The mean follow-up time was 60.5 months (SD=31.3). Eight patients (33%) developed recurrent lesions and a mean of disease-free interval for recurrent lesions of 19 months (SD=4.9). All recurrence lesions were diagnosed in two first years of follow-up and were significantly associated with: 1) poor clinical response to decompression (P=0.027); 2) remaining tooth with radiographic evidence of insinuation of the lesion between the dental roots (P=0.009); 3) presence of budding of the basal cells layer together with epithelial islands in the fibrous capsule (P=0.019). Our study suggests that these clinical, radiographic and microscopic parameters could affect relapse rate of patients with OKC and may individually guide the treatment choice

Diving fatality investigations: recent changes.

Modifications to the investigation procedures in diving fatalities have been incorporated into the data acquisition by diving accident investigators. The most germane proposal for investigators assessing diving fatalities is to delay the drawing of conclusions until all relevant diving information is known. This includes: the accumulation and integration of the pathological data; the access to dive computer information; re-enactments of diving incidents; post-mortem CT scans and the interpretation of intravascular and tissue gas detected. These are all discussed, with reference to the established literature and recent publications.

Sample size requirement for comparison of decompression outcomes using ultrasonically detected venous gas emboli (VGE): power calculations using Monte Carlo resampling from real data.

INTRODUCTION: In studies of decompression procedures, ultrasonically detected venous gas emboli (VGE) are commonly used as a surrogate outcome if decompression sickness (DCS) is unlikely to be observed. There is substantial variability in observed VGE grades, and studies should be designed with sufficient power to detect an important effect. METHODS: Data for estimating sample size requirements for studies using VGE as an outcome is provided by a comparison of two decompression schedules that found corresponding differences in DCS incidence (3/192 [DCS/dives] vs. 10/198) and median maximum VGE grade (2 vs. 3, P < 0.0001, Wilcoxon test). Sixty-two subjects dived each schedule at least once, accounting for 183 and 180 man-dives on each schedule. From these data, the frequency with which 10,000 randomly resampled, paired samples of maximum VGE grade were significantly different (paired Wilcoxon test, one-sided P ⋜ 0.05 or 0.025) in the same direction as the VGE grades of the full data set were counted (estimated power). Resampling was also used to estimate power of a Bayesian method that ranks two samples based on DCS risks estimated from the VGE grades. RESULTS: Paired sample sizes of 50 subjects yielded about 80% power, but the power dropped to less than 50% with fewer than 30 subjects. CONCLUSIONS: Comparisons of VGE grades that fail to find a difference between paired sample sizes of 30 or fewer must be interpreted cautiously. Studies can be considered well powered if the sample size is 50 even if only a one-grade difference in median VGE grade is of interest.

Colonic volvulus in the United States: trends, outcomes, and predictors of mortality.

INTRODUCTION: Colonic volvulus is a rare entity associated with high mortality rates. Most studies come from areas of high endemicity and are limited by small numbers. No studies have investigated trends, outcomes, and predictors of mortality at the national level. METHODS: The Nationwide Inpatient Sample 2002-2010 was retrospectively reviewed for colonic volvulus cases admitted emergently. Patients' demographics, hospital factors, and outcomes of the different procedures were analyzed. The LASSO algorithm for logistic regression was used to build a predictive model for mortality in cases of sigmoid (SV) and cecal volvulus (CV) taking into account preoperative and operative variables. RESULTS: An estimated 3,351,152 cases of bowel obstruction were admitted in the United States over the study period. Colonic volvulus was found to be the cause in 63,749 cases (1.90%). The incidence of CV increased by 5.53% per year whereas the incidence of SV remained stable. SV was more common in elderly males (aged 70 years), African Americans, and patients with diabetes and neuropsychiatric disorders. In contrast, CV was more common in younger females. Nonsurgical decompression alone was used in 17% of cases. Among cases managed surgically, resective procedures were performed in 89% of cases, whereas operative detorsion with or without fixation procedures remained uncommon. Mortality rates were 9.44% for SV, 6.64% for CV, 17% for synchronous CV and SV, and 18% for transverse colon volvulus. The LASSO algorithm identified bowel gangrene and peritonitis, coagulopathy, age, the use of stoma, and chronic kidney disease as strong predictors of mortality. CONCLUSIONS: Colonic volvulus is a rare cause of bowel obstruction in the United States and is associated with high mortality rates. CV and SV affect different populations and the incidence of CV is on the rise. The presence of bowel gangrene and coagulopathy strongly predicts mortality, suggesting that prompt diagnosis and management are essential.

Decompression tables for inside chamber attendants working at altitude.

INTRODUCTION: Hyperbaric oxygen (HBO2) multiplace chamber inside attendants (IAs) are at risk for decompression sickness (DCS). Standard decompression tables are formulated for sea-level use, not for use at altitude. METHODS: At Presbyterian/St. Luke's Medical Center (Denver, Colorado, 5,924 feet above sea level) and Intermountain Medical Center (Murray, Utah, 4,500 feet), the decompression obligation for IAs is managed with U.S. Navy Standard Air Tables corrected for altitude, Bühlmann Tables, and the Nobendem© calculator. IAs also breathe supplemental oxygen while compressed. Presbyterian/St. Luke's (0.83 atmospheres absolute/atm abs) uses gauge pressure, uncorrected for altitude, at 45 feet of sea water (fsw) (2.2 atm abs) for routine wound care HBO2 and 66 fsw (2.8 atm abs) for carbon monoxide/cyanide poisoning. Presbyterian/St. Luke's provides oxygen breathing for the IAs at 2.2 atm abs. At Intermountain (0.86 atm abs), HBO2 is provided at 2.0 atm abs for routine treatments and 3.0 atm abs for carbon monoxide poisoning. Intermountain IAs breathe intermittent 50% nitrogen/50% oxygen at 3.0 atm abs and 100% oxygen at 2.0 atm abs. The chamber profiles include a safety stop. RESULTS: From 1990-2013, Presbyterian/St. Luke's had 26,900 total IA exposures: 25,991 at 45 fsw (2.2 atm abs) and 646 at 66 fsw (2.8 atm abs); there have been four cases of IA DCS. From 2008-2013, Intermountain had 1,847 IA exposures: 1,832 at 2 atm abs and 15 at 3 atm abs, with one case of IA DCS. At both facilities, DCS incidents occurred soon after the chambers were placed into service. CONCLUSIONS: Based on these results, chamber inside attendant risk for DCS at increased altitude is low when the inside attendants breathe supplemental oxygen.

Are lumbar spine reoperation rates falling with greater use of fusion surgery and new surgical technology?

STUDY DESIGN: A retrospective analysis of population-based hospital discharge registry from all nonfederal acute care hospitals in Washington State. OBJECTIVE: We examined the cumulative incidence of second lumbar spine operation following an initial lumbar operation for degenerative conditions. We aimed to determine if the cumulative incidence of a second lumbar spine operation decreased in the 1990s following an increase in the rate of fusion surgery and the introduction of several newer fusion technologies. SUMMARY OF BACKGROUND DATA: Repeat lumbar spine operations are generally undesirable, implying persistent symptoms, progression of degenerative changes, or treatment complications. Improved technology is expected to improve alignment, healing, and instability, and to reduce repeat operations. METHODS: Among the patients who had an inpatient lumbar decompression or lumbar fusion surgery for degenerative spine disorders in 1990 to 1993 (n = 24,882) or in 1997 to 2000 (n = 25,209), we examined rates of subsequent lumbar spine surgery during a 4-year follow-up. We performed a Cox proportional hazards regression to compare the probability of a reoperation between the 2 cohorts, adjusting for age, sex, primary diagnosis, type of insurance, and comorbidity. RESULTS: Among patients who underwent surgery for lumbar degenerative disease, more than twice as many had a fusion procedure in the 1997 to 2000 cohort (19.1%) compared with the 1990 to 1993 cohort (9.4%). However, the 4-year cumulative incidence of reoperation was higher in the 1997 to 2000 cohort compared with the 1990 to 1993 cohort (14.0% vs. 12.4%; hazard ratio, 1.16; 95% confidence interval, 1.11-1.22, P < 0.001). Among fusion patients, those in the 1997 to 2000 cohort were approximately 40% more likely to undergo a reoperation within the first year when compared with fusion patients in the 1990 to 1993 cohort. There was no difference in reoperation probability beyond 1 year. CONCLUSION: A higher proportion of fusion procedures and the introduction of new spinal implants between 1993 and 1997 did not reduce reoperation rates. Patients who had lumbar surgery for degenerative disease in the late 1990s were more likely to undergo a repeat operation within 4 years than patients who had surgery in the early 1990s.

Prehospital intubation and chest decompression is associated with unexpected survival in major thoracic blunt trauma.

OBJECTIVE: Application of the Trauma and Injury Severity Score (TRISS) to a trauma population identifies patients with 'unexpected survival'. This study used TRISS analysis to identify 'unexpected survivors' suffering major thoracic trauma, who survived to hospital discharge. Further analysis determined prehospital interventions that appeared to contribute to 'unexpected survival'. METHODS: The present study was a single-centre, retrospective case review with comparative statistical analysis. Patients were identified from the Alfred Trauma Registry between 1 July 2002 and 30 June 2003. RESULTS: There were 336 adult trauma patients treated at The Alfred Trauma Centre with an Injury Severity Score >15 (major trauma) and at least one thoracic Anatomical Injury Score of 3 (severe) or greater. Of the eligible patients, 322/336 (95.8%, 95%[confidence interval] CI 95.1-96.5%) had complete data available for analysis. The study population mortality was 42/322 (13.0%, 95% CI 12.3-13.7%). There were 20 'unexpected survivors' (5.9%) and 5 (1.5%) 'unexpected deaths' on TRISS analysis. Chest decompression and/or endotracheal intubation prehospital was performed on 16/20 'unexpected survivors'. GCS for 'unexpected survivors' and 'expected deaths' (3.8 vs 3.5, P = 0.27) was not a predictor of survival. Respiratory rate per minute (16.2 vs 8.8, P = 0.01) and systolic blood pressure - mmHg (98 vs 80, P = 0.03) were significantly greater in the 'unexpected survivors' group compared with the 'expected death' group. CONCLUSION: For patients sustaining severe thoracic blunt trauma, prehospital intubation and chest decompression appear to be associated with unexpected survival. A low GCS at scene is not predictive of 'unexpected survival' or 'expected death'.

Evolution of relation P1(P2) describing saturation decompressions after air hyperbaric expositions.

The basic problem in decompression is the limit of maximum tolerable change of pressure after diving. Due to the number of parameters involved in decompression models (bottom time, ambient pressure, exposition profile, content of breathing mixtures, properties of inert gases) the number of possible solutions is theoretically unlimited. Since the beginning of modern decompression models the starting point has been direct saturation decompression using air. The generally accepted form of solution is the linear relation between tolerable pressure P2 after saturation exposition to pressure P1 described by the equation in the form P1 = P2 x A + B, where A and B are parameters obtained by experiments. Since the introduction of this equation values of parameters have been changing in order to decrease the rate of decompression illness. The aim of this study was to analyse and interpret the trend of those changes. Sixteen published models, including the one developed in our center, were compared and gradual change of parameters was identified. This trend should result in safer decompression systems.

Sleep patterns during 30-m nitrox simulated saturation dives.

The sleep patterns were examined during the simulated 30-m nitrox saturation dives. The standard polysomnography of 15 divers was recorded for a total of 255 nights, as were patterns of change or consistency in sleep variables. A reduction of total sleep time in accordance with the lengthening of sleep latency and the wake after sleep onset was observed through the latter part of the bottom period to the post-dive period, but the other sleep variables did not show any changes. These findings suggest that decompression and the psychological stress due to being in the closed environment of a hyperbaric chamber for a long time have effects on divers' sleep.

[The monitoring of gas bubbles with a pulsed Doppler ultrasonic locator in humans working in a space suit]. / Monitoring gazovykh puzyr'kov ul'trazvukovym impul'sno-dopplerovskim lokatorom u cheloveka pri rabote v skafandre.

Presented are results of gas bubbles monitoring in decompressed humans with the use of an ultrasonic pulse-Doppler locator (PDL). Unlike the classic Doppler bubbles detectors with continuous US emission, PDL is adjusted for reception of echo from a chosen volume of the right ventricle cavity; thus, the clutter due to cardiac beats and human locomotion is successfully rejected. During simulation of Russian EVAs, venous gas bubbles were detected in 3 out of 5 experiments with test-subjects clothed in everyday wear and in 2 out of 3 experiments with suited test-subjects.

[A method for evaluating the safety of decompression regimens for divers]. / Sposob otsenki bezopasnosti rezhimov dekompressii vodolazov.

The authors offer a way of estimation of safety modes of decompression, based on definition of intensity of venous gas embolism (VGE) at each decompression and account of probability of illness of divers in series of tests. Intensity of VGE was determined with the help of ultrasonic gas bubbles Doppler radar. Comparative safety of standard modes of decompression of divers of the Navy was estimated, and also the modes, designed in accordance with mathematical model of decompression, offered by I. A. Voitsekhovich (1990), were done. The results testify, that use of ultrasonic radar for estimation of intensity of VGE at decompression and account of average and maximum probability of decompression illness in series of tests of modes permit to receive the comparative characteristic of safety of modes at small number of decompressions.