Time-varying Spectral Index of Electrodermal Activity to Predict Central Nervous System Oxygen Toxicity Symptoms in Divers: Preliminary results.

The most effective method to mitigate decompression sickness in divers is hyperbaric oxygen (HBO2) pre-breathing. However, divers breathing HBO2 are at risk for developing central nervous system oxygen toxicity (CNS-OT), which can manifest as symptoms that might impair a diver's performance, or cause more serious symptoms like seizures. In this study, we have collected electrodermal activity (EDA) signals in fifteen subjects at elevated oxygen partial pressures (2.06 ATA, 35 FSW) in the "foxtrot" chamber pool at the Duke University Hyperbaric Center, while performing a cognitive stress test for up to 120 minutes. Specifically, we have computed the time-varying spectral analysis of EDA (TVSymp) as a tool for sympathetic tone assessment and evaluated its feasibility for the prediction of symptoms of CNS-OT in divers. The preliminary results show large increase in the amplitude TVSymp values derived from EDA recordings ~2 minutes prior to expert human adjudication of symptoms related to oxygen toxicity. An early detection based on TVSymp might allow the diver to take countermeasures against the dire consequences of CNS-OT which can lead to drowning.Clinical Relevance-This study provides a sensitive analysis method which indicates a significant increase in the electrodermal activity prior to human expert adjudication of symptoms related to CNS-OT.

Ultrasound in decompression research: fundamentals, considerations, and future technologies.

It is widely accepted that bubbles are a necessary but insufficient condition for the development of decompression sickness. However, open questions remain regarding the precise formation and behavior of these bubbles after an ambient pressure reduction (decompression), primarily due to the inherent difficulty of directly observing this phenomenon in vivo. In decompression research, information about these bubbles after a decompression is gathered via means of ultrasound acquisitions. The ability to draw conclusions regarding decompression research using ultrasound is highly influenced by the variability of the methodologies and equipment utilized by different research groups. These differences play a significant role in the quality of the data and thus the interpretation of the results. The purpose of this review is to provide a technical overview of the use of ultrasound in decompression research, particularly Doppler and brightness (B)-mode ultrasound. Further, we will discuss the strengths and limitations of these technologies and how new advancements are improving our ability to understand bubble behavior post-decompression.

A fully automated method for late ventricular diastole frame selection in post-dive echocardiography without ECG gating.

Venous gas emboli (VGE) are often quantified as a marker of decompression stress on echocardiograms. Bubble-counting has been proposed as an easy to learn method, but remains time-consuming, rendering large dataset analysis impractical. Computer automation of VGE counting following this method has therefore been suggested as a means to eliminate rater bias and save time. A necessary step for this automation relies on the selection of a frame during late ventricular diastole (LVD) for each cardiac cycle of the recording. Since electrocardiograms (ECG) are not always recorded in field experiments, here we propose a fully automated method for LVD frame selection based on regional intensity minimization. The algorithm is tested on 20 previously acquired echocardiography recordings (from the original bubble-counting publication), half of which were acquired at rest (Rest) and the other half after leg flexions (Flex). From the 7,140 frames analyzed, sensitivity was found to be 0.913 [95% CI: 0.875-0.940] and specificity 0.997 [95% CI: 0.996-0.998]. The method's performance is also compared to that of random chance selection and found to perform significantly better (p≺0.0001). No trend in algorithm performance was found with respect to VGE counts, and no significant difference was found between Flex and Rest (p>0.05). In conclusion, full automation of LVD frame selection for the purpose of bubble counting in post-dive echocardiography has been established with excellent accuracy, although we caution that high quality acquisitions remain paramount in retaining high reliability.

The Dewey monitor: Pulse oximetry can independently detect hypoxia in a rebreather diver.

Rebreather diving has one of the highest fatality rates per man hour of any diving activity in the world. The leading cause of death is hypoxia, typically from equipment or procedural failures. Hypoxia causes very few symptoms prior to causing loss of consciousness. Additionally, since the electronics responsible for controlling oxygen levels in rebreathers often control their alarm systems, frequently divers do not receive any external warnings. This study investigated the use of a forehead pulse oximeter as an independent warning device in the event of rebreather failure. Ten test subjects (seven male, three female, median age 29, range 26-35) exercised at a targeted rate of 2 L/minute oxygen consumption while on a non-functional rebreather breathing loop (mean consumption achieved 2.09 ± 0.36 L/minute). Each subject was tested both at the surface and at pressurized depth of 77 fsw (starting pO2=0.7 atm). The data show that a pulse oximeter could be used to provide an Mk 16 rebreather diver with a minimum mean of 49 seconds (± 17 seconds SD) of warning time after a noticeable change in blood oxygen saturation (SpO2 ≤ 95%) but before any risk of loss of consciousness (calculated SpO2 ≤ 80%), so that the diver may take mitigating actions. No statistical difference in warning time was found between the tests at surface and at 77 fsw (P=0.46).

Hypercapnia in diving: a review of CO2 retention in submersed exercise at depth.

Carbon dioxide (CO2) retention, or hypercapnia, is a known risk of diving that can cause mental and physical impairments leading to life-threatening accidents. Often, such accidents occur due to elevated inspired carbon dioxide. For instance, in cases of CO2 elimination system failures during rebreather dives, elevated inspired partial pressure of carbon dioxide (PCO2) can rapidly lead to dangerous levels of hypercapnia. Elevations in PaCO2 (arterial pressure of PCO2) can also occur in divers without a change in inspired PCO2. In such cases, hypercapnia occurs due to alveolar hypoventilation. Several factors of the dive environment contribute to this effect through changes in minute ventilation and dead space. Predominantly, minute ventilation is reduced in diving due to changes in respiratory load and associated changes in respiratory control. Minute ventilation is further reduced by hyperoxic attenuation of chemosensitivity. Physiologic dead space is also increased due to elevated breathing gas density and to hyperoxia. The Haldane effect, a reduction in CO2 solubility in blood due to hyperoxia, may contribute indirectly to hypercapnia through an increase in mixed venous PCO2. In some individuals, low ventilatory response to hypercapnia may also contribute to carbon dioxide retention. This review outlines what is currently known about hypercapnia in diving, including its measurement, cause, mental and physical effects, and areas for future study.

Sildenafil: Possible Prophylaxis against Swimming-induced Pulmonary Edema.

Swimming-induced pulmonary edema (SIPE) occurs during swimming and scuba diving, usually in cold water, in susceptible healthy individuals, especially military recruits and triathletes. We have previously demonstrated that pulmonary artery (PA) pressure and PA wedge pressure are higher during immersed exercise in SIPE-susceptible individuals versus controls, confirming that SIPE is a form of hemodynamic pulmonary edema. Oral sildenafil 50 mg 1 h before immersed exercise reduced PA pressure and PA wedge pressure, suggesting that sildenafil may prevent SIPE. We present a case of a 46-yr-old female ultratriathlete with a history of at least five SIPE episodes. During a study of an exercise submerged in 20°C water, physiological parameters before and after sildenafil 50 mg orally were as follows: O2 consumption 1.75, 1.76 L·min; HR 129, 135 bpm; arterial pressure 189/88 (mean 121.5), 172/85 (mean 114.3) mm Hg; mean PA pressure 35.3, 28.8 mm Hg; and PA wedge pressure 25.3, 19.7 mm Hg. She has had no recurrences during 20 subsequent triathlons while taking 50 mg sildenafil before each swim. This case supports sildenafil as an effective prophylactic agent against SIPE during competitive surface swimming.

Swimming-Induced Pulmonary Edema: Pathophysiology and Risk Reduction With Sildenafil.

BACKGROUND: Swimming-induced pulmonary edema (SIPE) occurs during swimming or scuba diving, often in young individuals with no predisposing conditions, and its pathophysiology is poorly understood. This study tested the hypothesis that pulmonary artery and pulmonary artery wedge pressures are higher in SIPE-susceptible individuals during submerged exercise than in the general population and are reduced by sildenafil. METHODS AND RESULTS: Ten study subjects with a history of SIPE (mean age, 41.6 years) and 20 control subjects (mean age, 36.2 years) were instrumented with radial artery and pulmonary artery catheters and performed moderate cycle ergometer exercise for 6 to 7 minutes while submersed in 20°C water. SIPE-susceptible subjects repeated the exercise 150 minutes after oral administration of 50 mg sildenafil. Work rate and mean arterial pressure during exercise were similar in controls and SIPE-susceptible subjects. Average o2 and cardiac output in controls and SIPE-susceptible subjects were: o2 2.42 L·min(-1) versus 1.95 L·min(-1), P=0.2; and cardiac output 17.9 L·min(-1) versus 13.8 L·min(-1), P=0.01. Accounting for differences in cardiac output between groups, mean pulmonary artery pressure at cardiac output=13.8 L·min(-1) was 22.5 mm Hg in controls versus 34.0 mm Hg in SIPE-susceptible subjects (P=0.004), and the corresponding pulmonary artery wedge pressure was 11.0 mm Hg versus 18.8 mm Hg (P=0.028). After sildenafil, there were no statistically significant differences in mean pulmonary artery pressure or pulmonary artery wedge pressure between SIPE-susceptible subjects and controls. CONCLUSIONS: These observations confirm that SIPE is a form of hemodynamic pulmonary edema. The reduction in pulmonary vascular pressures after sildenafil with no adverse effect on exercise hemodynamics suggests that it may be useful in SIPE prevention. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00815646.

Research report: Charcoal type used for hookah smoking influences CO production.

A hookah smoker who was treated for severe carbon monoxide poisoning with hyperbaric oxygen reported using a different type of charcoal prior to hospital admission, i.e., quick-light charcoal. This finding led to a study aimed at determining whether CO production differs between charcoals commonly used for hookah smoking, natural and quick-light. Our hypothesis was that quick-light charcoal produces significantly more CO than natural charcoal. A medium-sized hookah, activated charcoal filter, calibrated syringe, CO gas analyzer and infrared thermometer were assembled in series. A single 9-10 g briquette of either natural or quick-light charcoal was placed atop the hookah bowl and ignited. CO output (ppm) and temperature (degrees C) were measured in three-minute intervals over 90 minutes. The mean CO levels produced by quick-light charcoal over 90 minutes was significantly higher (3728 ± 2028) compared to natural charcoal (1730 ± 501 ppm, p = 0.016). However, the temperature was significantly greater when burning natural charcoal (292 ± 87) compared to quick-light charcoal (247 ± 92 degrees C, p = 0.013). The high levels of CO produced when using quick-light charcoals may be contributing to the increase in reported hospital admissions for severe CO poisoning.

Safe administration of hyperbaric oxygen after bleomycin: a case series of 15 patients.

INTRODUCTION: Supplemental oxygen has been reported to cause pulmonary complications after bleomycin. We describe the safe administration of hyperbaric oxygen (HBO2) after bleomycin in 15 patients. METHODS: Paper and electronic records were reviewed for bleomycin-exposed patients at the Duke Center for Hyperbaric Medicine and Environmental Physiology from 1979 to 2010. RESULTS: Fourteen bleomycin-exposed patients received HBO2 at Duke under a special-precautions protocol. One was treated for DCS elsewhere. The protocol included: pretreatment evaluation; chest radiograph; spirometry; blood gases; a single, 2-atmospheres absolute (atm abs), 120-minute HBO2 treatment; and a gradual acceleration over one week to a twice-daily schedule contingent on clinical and laboratory findings. Bleomycin indications were: head-and-neck squamous cell carcinomas (11), Hodgkin's lymphoma (2), other carcinomas (2). HBO2 indications were: osteoradionecrosis (10), soft-tissue radionecrosis (3), DCS (1) and a provocative oxygen toxicity test for a military aviator (1). Total bleomycin doses ranged from 40 to 225u/m2 (mean +/- SD, 105 +/- 57) given in conjunction with other chemotherapies and/or radiation. Radiation was 63.3 +/- 31.72 Gy (mean +/- SD), none to the chest with the exception of one patient treated for DCS elsewhere. Other chemotherapies included: vinblastine (11), methotrexate (11), CCNU (6) cisplatinum (7), dacarbazin (2), Adriamycin (1), and vincristine (1). Median age at time of HBO2 was 52 years (range 22-77). Median bleomycin-to-HBO2 latency was 34 months (range 1-279). Three patients received HBO2 within six months, and seven patients received HBO2 within two years of their last bleomycin exposure. There were no adverse pre-to-post HBO2 changes in: arterial blood gases, spirometry, chest radiograph findings or clinical reports. There were no persistent post-HBO2 pulmonary complications on follow-up. Post-HBO2 data were available for 40%, 53%, 87% and 100% of these parameters respectively. DISCUSSION: Bleomycin and oxygen can individually cause acute pulmonary toxicity. However, evidence for increased long-term susceptibility based on their synergy may be overstated.

What is the role of hyperbaric oxygen in the management of bisphosphonate-related osteonecrosis of the jaw: a randomized controlled trial of hyperbaric oxygen as an adjunct to surgery and antibiotics.

PURPOSE: This study tested hyperbaric oxygen (HBO) as an adjunct to surgery and antibiotics in the treatment of bisphosphonate-related osteonecrosis of the jaw (ONJ) and evaluated its effects on gingival healing, pain, and quality of life. MATERIALS AND METHODS: The investigators implemented a randomized controlled trial and enrolled a sample composed of patients with ONJ, where the predictor variable was HBO administered at 2 atm twice a day for 40 treatments as an adjunct to conventional therapy of surgery and antibiotics versus conventional therapy alone. Over the next 24 months, oral lesion size and number, pain, and quality of life were assessed. RESULTS: Forty-six patients (mean age, 66 yrs; 57% women) contributed data to the trial. There were no statistically significant differences in the distribution of variables used to assess randomization success between the HBO and standard treatment groups. Seventeen of 25 HBO-treated patients (68%) improved versus 8 of 21 controls (38.1%; P = .043, χ(2) test). Mean time to improvement was 39.7 weeks (95% confidence interval [CI], 22.4 to 57.0 weeks) for HBO-treated patients versus 67.9 weeks (95 CI, 48.4 to 87.5 weeks) for controls (P = .03, log-rank test). However, complete gingival healing occurred in only 14 of 25 HBO-treated patients (52%) versus 7 of 21 controls (33.3%; P = .203, χ(2) test), and time to healing was 59 weeks (95% CI, 42.8% to 75.8%) for HBO-treated patients versus 70 weeks (95 CI, 52.2% to 88.36%) for controls (P = .32, log-rank test). Pain decreased faster for HBO-treated subjects (P < .01, linear regression). Quality-of-life scores for physical health (P = .002) and perceived health (P = .043) decreased at 6 months for control group but for not the HBO group. CONCLUSIONS: ONJ is multifactorial and no single treatment modality is likely to reverse it; however, it is treatable and even advanced presentations can improve with intensive multimodal therapy. Clinically, HBO appears to be a useful adjunct to ONJ treatment, particularly for more severe cases, although this study was underpowered to fully support this claim.

Hyperbaric oxygen therapy in necrotising soft tissue infections: a study of patients in the United States Nationwide Inpatient Sample.

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.

Effects of hyperoxia on ventilation and pulmonary hemodynamics during immersed prone exercise at 4.7 ATA: possible implications for immersion pulmonary edema.

Immersion pulmonary edema (IPE) can occur in otherwise healthy swimmers and divers, likely because of stress failure of pulmonary capillaries secondary to increased pulmonary vascular pressures. Prior studies have revealed progressive increase in ventilation [minute ventilation (Ve)] during prolonged immersed exercise. We hypothesized that this increase occurs because of development of metabolic acidosis with concomitant rise in mean pulmonary artery pressure (MPAP) and that hyperoxia attenuates this increase. Ten subjects were studied at rest and during 16 min of exercise submersed at 1 atm absolute (ATA) breathing air and at 4.7 ATA in normoxia and hyperoxia [inspired P(O(2)) (Pi(O(2))) 1.75 ATA]. Ve increased from early (E, 6th minute) to late (L, 16th minute) exercise at 1 ATA (64.1 +/- 8.6 to 71.7 +/- 10.9 l/min BTPS; P < 0.001), with no change in arterial pH or Pco(2). MPAP decreased from E to L at 1 ATA (26.7 +/- 5.8 to 22.7 +/- 5.2 mmHg; P = 0.003). Ve and MPAP did not change from E to L at 4.7 ATA. Hyperoxia reduced Ve (62.6 +/- 10.5 to 53.1 +/- 6.1 l/min BTPS; P < 0.0001) and MPAP (29.7 +/- 7.4 to 25.1 +/- 5.7 mmHg, P = 0.002). Variability in MPAP among subjects was wide (range 14.1-42.1 mmHg during surface and depth exercise). Alveolar-arterial Po(2) difference increased from E to L in normoxia, consistent with increased lung water. We conclude that increased Ve at 1 ATA is not due to acidosis and is more consistent with respiratory muscle fatigue and that progressive pulmonary vascular hypertension does not occur during prolonged immersed exercise. Wide variation in MPAP among healthy subjects is consistent with variable individual susceptibility to IPE.

Resolution and severity in decompression illness.

omegaWe review the terminology of decompression illness (DCI), investigations of residual symptoms of decompression sickness (DCS), and application of survival analysis for investigating DCI severity and resolution. The Type 1 and Type 2 DCS classifications were introduced in 1960 for compressed air workers and adapted for diving and altitude exposure with modifications based on clinical judgment concerning severity and therapy. In practice, these proved ambiguous, leading to recommendations that manifestations, not cases, be classified. A subsequent approach assigned individual scores to manifestations and correlated total case scores with the presence of residual symptoms after therapy. The next step used logistic regression to find the statistical association of manifestations to residual symptoms at a single point in time. Survival analysis, a common statistical method in clinical trials and longitudinal epidemiological studies, is a logical extension of logistic regression. The method applies to a continuum of resolution times, allows for time varying information, can manage cases lost to follow-up (censored), and has potential for investigating questions such as optimal therapy and DCI severity. There are operational implications as well. Appropriate definitions of mild and serious manifestations are essential for computing probabilistic decompression procedures where severity determines the DCS probability that is acceptable. Application of survival analysis to DCI data would require more specific case information than is commonly recorded.

Utility of hyperbaric oxygen in treatment of bisphosphonate-related osteonecrosis of the jaws.

Bisphosphonates suppress bone turnover by disrupting osteoclast signal transduction, maturation, and longevity. In some patients, it has been hypothesized that suppressed turnover can impair oral wound healing, leading to a distressing, osteopetrosis-like jaw necrosis called bisphosphonate-related osteonecrosis of the jaws (BRONJ). Hyperbaric oxygen (HBO), as an adjunct to surgery and antibiotics, might have utility in the treatment of BRONJ because it produces reactive oxygen and nitrogen species that positively modulate the redox-sensitive intracellular signaling molecules involved in bone turnover. The efficacy of HBO in the treatment of BRONJ is currently under investigation in randomized controlled trials at Duke University and the University of Minnesota, and the early results have been encouraging. This report discusses osteoclast biology, how HBO has the potential to augment bone turnover by way of the signaling effects on osteoclasts, the available clinical data on HBO in the treatment of BRONJ, the ongoing randomized controlled trials of HBO, and the study-associated efforts to find biomarkers to characterize an individual's risk of developing this disease.

Multimodality surgical and hyperbaric management of mandibular osteoradionecrosis.

PURPOSE: To elucidate long-term outcomes in 65 consecutive patients meeting a uniform definition of mandibular osteoradionecrosis (ORN) treated with multimodality therapy including hyperbaric oxygen (HBO). METHODS AND MATERIALS: Pretreatment, post-treatment and long-term follow-up of mandibular lesions with exposed bone were ranked by a systematic review of medical records and patient telephone calls. The ranking system was based on lesion diameter and number plus disease progression. Changes from pretreatment to post-treatment and follow-up were analyzed by Wilcoxon signed-rank tests. Improved wound survival, measured by time to relapse, defined as any less favorable rank after HBO treatment, was assessed by Kaplan-Meier analysis. RESULTS: In all, 57 cases (88%) resolved or improved by lesion grade or progression and evolution criteria after HBO (p < 0.001). Four patients healed before surgery after HBO alone. Of 57 patients who experienced improvement, 41 had failed previous nonmultimodality therapy for 3 months and 26 for 6 months or more. A total of 43 patients were eligible for time-to-relapse survival analysis. Healing or improvement lasted a mean duration of 86.1 months (95% confidence interval [95% CI], 64.0-108.2) in nonsmokers (n = 20) vs. 15.8 months (95% CI, 8.4-23.2) in smokers (n = 14) versus 24.2 months (95% CI, 15.2-33.2) in patients with recurrent cancer (n = 9) (p = 0.002 by the log-rank method). CONCLUSIONS: Multimodality therapy using HBO is effective for ORN when less intensive therapies have failed. Although the healing rate in similarly affected patients not treated with HBO is unknown, the improvements seen with peri-operative HBO were durable provided that the patients remained cancer free and abstained from smoking.

Hyperbaric oxygen treatment and bisphosphonate-induced osteonecrosis of the jaw: a case series.

PURPOSE: Bisphosphonate (BP)-associated osteonecrosis of the jaw (ONJ) is an emerging problem with few therapeutic options. Our pilot study of BP-ONJ investigated a possible role for hyperbaric oxygen (HBO(2)) therapy. PATIENTS AND METHODS: A total of 16 patients, ranging in age from 43 to 78 years, with BP-ONJ were treated with adjunctive HBO(2) between July 2003 and April 2006. Staging was based on the size and number of oral lesions. Clinical response after treatment and at distant follow-up; the odds of remission, stabilization, or relapse; and time to failure analysis were calculated. RESULTS: The median time on BP therapy before appearance of ONJ symptoms was 18 months, and that from symptom onset to HBO(2) therapy was 12 months. Fourteen of 16 patients (87.5%) improved in stage. The size and number of ONJ lesions were decreased after HBO(2) therapy (P < .001 and P = .008, respectively; Wilcoxon signed-rank test). Immediately after HBO(2) therapy, 7 of 16 patients (44%) were in remission and 8 (50%) had stabilized; however, stabilization without remission was sustained in only 2 patients. At follow-up, 10 of the patients (62.5%) were still in remission or had stabilized. The 7 patients who continued on BP treatment during HBO(2) therapy had a shorter time to failure (8.5 months; 95% confidence interval [CI] = 7.1 to 9.8) than those who discontinued the drug (20.1 months; 95% CI = 17.5 to 23.9; P = .006 by the log-rank test). Clinical response was not associated with cancer type or malignancy remission status. CONCLUSIONS: Adjunctive HBO(2) therapy may benefit patients with BP-ONJ; however, the outcome is improved with cessation of BP administration.

A comparison of hyperbaric oxygen versus hypoxic cerebral preconditioning in neonatal rats.

The potency of hyperbaric preconditioning (HBO-PC) is uncertain compared to well-validated ischemic or hypoxic models and no studies have directly compared HBO-PC to hypoxic preconditioning (HPC). We subjected rat pups to unilateral carotid cauterization followed by 90 min (min) of hypoxia using 8% O(2). Three HBO-PC regimes (maximum 2.5 atmospheres for 150 min) were compared to HPC (150 min of 8% O(2)) for changes in mortality and brain weight. Preconditioning-induced oxidative stress was assessed using aconitase activity and manganese superoxide dismutase (MnSOD) transcript levels. Initial brain weight data revealed a large coefficient of variation and compelled an examination of the temperature sensitivity of the model that revealed a narrow optimal range of 35 to 37 degrees C of variability in brain injury and mortality. With rigorous temperature control, high dose HBO-PC and HPC showed comparable anatomic (mean hemispheric weight decrease: control 42%, HPC 25% (P=0.01), HBO-PC 26% (P=0.01) and mortality protection (control 14.7%, HPC 5.9% HBO-PC 5.7%, P=0.001). High dose HBO-PC, but not HPC, suppressed aconitase activity by 65% at 24 h after the preconditioning stimulus (P=0.001). In contrast, MnSOD mRNA increased 2.5-fold at 24 h after HPC (P=0.007) but not after high dose HBO-PC. Thus, when temperature variability is eliminated, HBO-PC and HPC elicit similar preconditioning efficacy in neonatal brain but invoke different defenses against oxidative stress.

Consensus factors used by experts in the diagnosis of decompression illness.

INTRODUCTION: The diagnosis of decompression illness (DCI) is entirely based on clinical findings and DCI experts are rare. Of all the chambers reporting to Diver's Alert Network (DAN), 86% see less than 10 cases per year. Simulated diving injury cases (vignettes) were used to identify diagnostic factors important to 11 international experts attending the 2003 Undersea and Hyperbaric Medical Society symposium on DCI diagnosis. METHODS: There were 200 vignettes evaluated for the probability of DCS and/or arterial gas embolism (AGE). Vignettes were constructed from 141 factors that modeled information from DAN's emergency call system. Factor probability mirrored DAN's 2001 Report on Decompression Illness and Diving Fatalities. Factors included: diver characteristics, exposure characteristics, signs, symptoms, treatment, and response. Multiple linear regression with stepwise elimination identified and ordered the significant factors in terms of their importance to the experts. Results were confirmed with logistic regression. RESULTS: For DCS, the top five factors in order of importance were: 1) a neurological symptom as the primary presenting symptom; 2) onset time of symptoms; 3) joint pain as a presenting symptom; 4) any relief after recompression treatment; and 5) the maximum depth of the last dive. For AGE, the top five factors were: 1) onset time of symptoms; 2) altered consciousness; 3) any neurological symptoms as a presenting symptom; 4) motor weakness; and 5) seizure as the primary presenting symptom. Age, gender, or physical characteristics were not statistically important. CONCLUSIONS: The vignette concept may be useful in the development of consensus standards for DCI diagnosis.