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Decompression illness is caused by intravascular or extravascular bubbles that are formed as a result of reduction in environmental pressure (decompression). The term covers both arterial gas embolism, in which alveolar gas or venous gas emboli (via cardiac shunts or via pulmonary vessels) are introduced into the arterial circulation, and decompression sickness, which is caused by in-situ bubble formation from dissolved inert gas. Both syndromes can occur in divers, compressed air workers, aviators, and astronauts, but arterial gas embolism also arises from iatrogenic causes unrelated to decompression. Risk of decompression illness is affected by immersion, exercise, and heat or cold. Manifestations range from itching and minor pain to neurological symptoms, cardiac collapse, and death. First-aid treatment is 100% oxygen and definitive treatment is recompression to increased pressure, breathing 100% oxygen. Adjunctive treatment, including fluid administration and prophylaxis against venous thromboembolism in paralysed patients, is also recommended. Treatment is, in most cases, effective although residual deficits can remain in serious cases, even after several recompressions.

Doppler ultrasound (DU) is used in decompression research to detect venous gas emboli in the precordium or subclavian vein, as a marker of decompression stress. This is of relevance to scuba divers, compressed air workers and astronauts to prevent decompression sickness (DCS) that can be caused by these bubbles upon or after a sudden reduction in ambient pressure. Doppler ultrasound data is graded by expert raters on the Kisman-Masurel or Spencer scales that are associated to DCS risk. Meta-analyses, as well as efforts to computer-automate DU grading, both necessitate access to large databases of well-curated and graded data. Leveraging previously collected data is especially important due to the difficulty of repeating large-scale extreme military pressure exposures that were conducted in the 70-90s in austere environments. Historically, DU data (Non-speech) were often captured on cassettes in one-channel audio with superimposed human speech describing the experiment (Speech). Digitizing and separating these audio files is currently a lengthy, manual task. In this paper, we develop a graphical user interface (GUI) to perform automatic speech recognition and aid in Non-speech and Speech separation. This constitutes the first study incorporating speech processing technology in the field of diving research. If successful, it has the potential to significantly accelerate the reuse of previously-acquired datasets. The recognition task incorporates the Google speech recognizer to detect the presence of human voice activity together with corresponding timestamps. The detected human speech is then separated from the audio Doppler ultrasound within the developed GUI. Several experiments were conducted on recently digitized audio Doppler recordings to corroborate the effectiveness of the developed GUI in recognition and separations tasks, and these are compared to manual labels for Speech timestamps. The following metrics are used to evaluate performance: the average absolute differences between the reference and detected Speech starting points, as well as the percentage of detected Speech over the total duration of the reference Speech. Results have shown the efficacy of the developed GUI in Speech/Non-speech component separation.

Doppler ultrasound (DU) measurements are used to detect and evaluate venous gas emboli (VGE) formed after decompression. Automated methodologies for assessing VGE presence using signal processing have been developed on varying real-world datasets of limited size and without ground truth values preventing objective evaluation. We develop and report a method to generate synthetic post-dive data using DU signals collected in both precordium and subclavian vein with varying degrees of bubbling matching field-standard grading metrics. This method is adaptable, modifiable, and reproducible, allowing for researchers to tune the produced dataset for their desired purpose. We provide the baseline Doppler recordings and code required to generate synthetic data for researchers to reproduce our work and improve upon it. We also provide a set of pre-made synthetic post-dive DU data spanning six scenarios representing the Spencer and Kisman-Masurel (KM) grading scales as well as precordial and subclavian DU recordings. By providing a method for synthetic post-dive DU data generation, we aim to improve and accelerate the development of signal processing techniques for VGE analysis in Doppler ultrasound.

Decompression sickness and arterial gas embolism have nonspecific symptoms and are easily misdiagnosed if a recent patient history of diving and potential iatrogenic causes of AGE are not kept in mind. The authors review the pathophysiology, clinical features, and treatment of these disorders.

Purpose Necrotising soft tissue infection (NSTI) is a deadly disease associated with a significant risk of mortality and long-term disability from limb and tissue loss. The aim of this study was to determine the effect of hyperbaric oxygen (HBO 2 ) therapy on mortality, complication rate, discharge status/location, hospital length of stay and inflation-adjusted hospitalisation cost in patients with NSTI. Methods This was a retrospective study of 45,913 patients in the Nationwide Inpatient Sample (NIS) from 1988 to 2009. Results A total of 405 patients received HBO 2 therapy. The patients with NSTI who received HBO 2 therapy had a lower mortality (4.5 vs. 9.4 %, p  = 0.001). After adjusting for predictors and confounders, patients who received HBO 2 therapy had a statistically significantly lower risk of dying (odds ratio (OR) 0.49, 95 % confidence interval (CI) 0.29–0.83), higher hospitalisation cost (US$52,205 vs. US$45,464, p  = 0.02) and longer length of stay (LOS) (14.3 days vs. 10.7 days, p  < 0.001). Conclusions This retrospective analysis of HBO 2 therapy in NSTI showed that despite the higher hospitalisation cost and longer length of stay, the statistically significant reduction in mortality supports the use of HBO 2 therapy in NSTI.

Interactions of nitric oxide (NO) with hemoglobin (Hb) could regulate the uptake and delivery of oxygen (O 2 ) by subserving the classical physiological responses of hypoxic vasodilation and hyperoxic vasconstriction in the human respiratory cycle. Here we show that in in vitro and ex vivo systems as well as healthy adults alternately exposed to hypoxia or hyperoxia (to dilate or constrict pulmonary and systemic arteries in vivo ), binding of NO to hemes (FeNO) and thiols (SNO) of Hb varies as a function of HbO 2 saturation (FeO 2 ). Moreover, we show that red blood cell (RBC)/SNO-mediated vasodilator activity is inversely proportional to FeO 2 over a wide range, whereas RBC-induced vasoconstriction correlates directly with FeO 2 . Thus, native RBCs respond to changes in oxygen tension (pO2) with graded vasodilator and vasoconstrictor activity, which emulates the human physiological response subserving O 2 uptake and delivery. The ability to monitor and manipulate blood levels of NO, in conjunction with O 2 and carbon dioxide, may therefore prove useful in the diagnosis and treatment of many human conditions and in the development of new therapies. Our results also help elucidate the link between RBC dyscrasias and cardiovascular morbidity.

Background Oxygen-rich breathing mixtures up to 100% are used in some underwater diving operations for several reasons. Breathing elevated oxygen partial pressures (PO 2 ) increases the risk of developing central nervous system oxygen toxicity (CNS-OT) which could impair performance or result in a seizure and subsequent drowning. We aimed to study the dynamics of the electrodermal activity (EDA) and heart rate (HR) while breathing elevated PO 2 in the hyperbaric environment (HBO 2 ) as a possible means to predict impending CNS-OT. Methods EDA is recorded during 50 subject exposures (26 subjects) to evaluate CNS-OT in immersed (head out of water) exercising divers in a hyperbaric chamber breathing 100% O 2 at 35 feet of seawater (FSW), (PO 2  = 2.06 ATA) for up to 120 min. Results 32 subject exposures exhibit symptoms “definitely” or “probably” due to CNS-OT before the end of the exposure, whereas 18 do not. We obtain traditional and time-varying spectral indices (TVSymp) of EDA to determine its utility as predictive physio markers. Variations in EDA and heart rate (HR) for the last 5 min of the experiment are compared to baseline values prior to breathing O 2 . In the subset of experiments where “definite” CNS-OT symptoms developed, we find a significant elevation in the mean ± standard deviation TVSymp value 57 ± 79 s and median of 10 s, prior to symptoms. Conclusions In this retrospective analysis, TVSymp may have predictive value for CNS-OT with high sensitivity (1.0) but lower specificity (0.48). Additional work is being undertaken to improve the detection algorithm. Plain Language Summary This study looked at the effects of breathing high levels of oxygen during underwater diving and the risk of central nervous system oxygen toxicity. This toxicity can cause problems with movement, seizures or even drowning. We wanted to see if changes in skin and heart activity could help predict the symptoms of toxicity. We tested 26 divers (50 dives) in a special chamber. They breathed pure oxygen at increased pressure (equivalent to being underwater at 35 feet). 32 dives showed signs of toxicity, while 18 did not. We looked at the electrodermal activity (a measurement of the skin conductance) and heart rate data to see if they could warn of an issue. We found that in dives where toxicity symptoms definitely developed, there were significant changes in electrodermal activity around 57 s before symptoms appeared. While this method was very sensitive, it wasn’t always specific. We are working on improving this prediction method. This may be used to warn divers of dangerous gases so they can switch breathing gases or move to a shallower depth, and can improve the chances of escaping a disabled submarine. Posada-Quintero et al. study the dynamics of the electrodermal activity and heart rate while breathing at elevated oxygen partial pressures in a hyperbaric environment. Electrodermal activitycan be used to predict the onset of central nervous system oxygen toxicity symptoms in divers resulting from prolonged exposure to a hyperbaric environment.

Background While enhanced recovery protocols (ERPs) reduce physiologic stress and improve outcomes in general, their effects on postoperative renal function have not been directly studied. Methods Patients undergoing major colorectal surgery under ERP (February 2010 to March 2013) were compared with a traditional care control group (October 2004 October 2007) at a single institution. Multivariable regression models examined the association of ERP with postoperative creatinine changes and incidence of postoperative acute kidney dysfunction (based on the Risk, Injury, Failure, Loss, and End-stage renal disease criteria). Results Included were 1054 patients: 590 patients underwent surgery with ERP and 464 patients without ERP. Patient demographics were not significantly different. Higher rates of neoplastic and inflammatory bowel disease surgical indications were found in the ERP group (81 vs. 74%, p  = 0.045). Patients in the ERP group had more comorbidities (ASA ≥ 3) (62 vs. 40%, p  < 0.001). In unadjusted analysis, postoperative creatinine increase was slightly higher in the ERP group compared with control (median 0.1 vs. 0 mg/dL, p  < 0.001), but levels of postoperative acute kidney injury were similar in both groups ( p  = 0.998). After adjustment with multivariable regression, postoperative changes in creatinine were similar in ERP vs. control ( p  = 0.25). Conclusions ERP in colorectal surgery is not associated with a clinically significant increase in postoperative creatinine or incidence of postoperative kidney injury. Our results support the safety of ERPs in colorectal surgery and may promote expanding implementation of these protocols. Trial registration Not applicable, prospective data collection and retrospective chart review only.