The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox.

Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window--also called inherent unsaturation or partial pressure vacancy--but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of decompression after saturation with nitrogen-based breathing mixtures.

Effect of oxygen on neuronal excitability measured by critical flicker fusion frequency is dose dependent.

INTRODUCTION: Reactive oxygen species are involved in the functional changes necessary for synaptic plasticity, memory, and cognitive function. It is far from clear whether the increased excitability, and which forms of neuronal excitability, should be considered a part of the learning process or, rather, cellular manifestation of neuronal oxygen poisoning. It is yet to be elucidated whether oxygen (O2)-induced learning and poisoning use the same or distinct cellular pathways. PURPOSE: We hypothesized that O2-induced neuronal excitability might use the same or an intertwined signaling cascade as the poisoning cellular pathway. METHOD: Eighty-one healthy, young males, mean age 27.7 ± 4.1 (SD) years, were exposed in the hyperbaric chamber to 0.7 atmosphere absolute (ATA) O2, 1.4 ATA O2, and 2.8 ATA O2. The critical flicker fusion frequency (CFFF), oxyhemoglobin saturation (SiO2), and heart rate (HR) were measured before exposure, after 30 min of oxygen breathing while still at pressure and then after exposure. RESULTS: Normobaric (0.7 ATA) O2 exposure did not affect CFFF and HR. Medium hyperbaric O2 exposure (1.4 ATA) decreased CFFF but HR remained unchanged. High hyperbaric O2 exposure (2.8 ATA) increased CFFF and diminished HR. SiO2 was similar in all investigated groups. A correlation between CFFF, HR, and SiO2 was observed only at low oxygen (0.7 ATA). CONCLUSIONS: The effect of O2 on neuronal excitability measured by CFFF in young healthy men was dose dependent: 0.7 ATA O2 did not affect CFFF; CFFF were significantly jeopardized at 1.4 ATA O2, while CFFF recovered at 2.8 ATA. With 2.8 ATA O2, the CFFF and oxygen poisoning transduction pathways seemed to be intertwined.

Coronary air embolism.

The case report of acute coronary episode caused by air embolism associated with the removal of central vascular access, published in "Anaesthesiology Intensive Therapy"1/2012 aroused much interest [1]. Iatrogenic gas emboli are rare, albeit dramatic complications of therapeutic interventions,which result in persistent neurological symptoms in over 40% of cases [2].

Hyperbaric oxygen therapy (HBOT) in case of hemorrhagic cystitis after radiotherapy.

INTRODUCTION: We present the effect of hyperbaric oxygen therapy (HBOT) after radiotherapy for cancer in the pelvic cavity resulting in hematuria. Increasing the pressure of oxygen (PO2) in ischemic tissues favors the formation of new blood vessels and increases the secretion of collagen. MATERIAL AND METHODS: We evaluated 10 patients who were treated with HBOT from October 2006 to December 2010 due to persistent radiation damage to the lining of the bladder leading to recurrent hematuria. The study group was comprised of seven men and three women. In the case of cervical and endometrial cancers, 30 Gy of brachytherapy with 45-50 Gy of teleradiotherapy were used. In prostate cancer (PCa), we applied 50 Gy of teleradiotherapy with an additional dose of 20-24 Gy, and in the case of bladder cancer (BCa), 50 Gy of teleradiotherapy was applied with an additional dose of 16 Gy. HBOT consisted of 60 HBO2 treatments, in which patients were administered 100% oxygen at a pressure of 2.5 atm. RESULTS: The group effect of total or partial resolution was observed in six patients. In one case, treatment was discontinued due to an increase in hematuria and the consequent suspicion of bladder tumor recurrence. While in and additional three cases, the treatment did not produce the desired result. CONCLUSIONS: Treatment of hemorrhagic cystitis is a difficult therapeutic challenge. One possible method is the implementation of HBOT. In very difficult cases, HBO2 treatment appears to be effective in giving more than half of patients a chance of getting better.

Recompression treatment for decompression illness: 5-year report (2003-2007) from National Centre for Hyperbaric Medicine in Poland.

A serious diving accident can occur in recreational diving even in countries where diving is not very popular due to the fact that diving conditions there are not as great as in some tropical diving locations. The estimated number of injured divers who need recompression treatment in European hyperbaric facilities varies between 10 and 100 per year depending on the number of divers in the population, number of dives performed annually, and number of hyperbaric centres in the country. In 5 years of retrospective observation in Poland (2003-2007) there were 51 cases of injured recreational divers recorded. They either dived locally or after returning home by air from a tropical diving resort. All of them were treated with recompression treatment in the National Centre for Hyperbaric Medicine in Gdynia which has capability to treat any patient with decompression illness using all currently available recompression schedules with any breathing mixtures including oxygen, nitrox, heliox or trimix. The time interval between surfacing and first occurrence of symptoms was significantly lower in the group of patients with neurological decompression sickness or arterial gas embolism (median 0.2 hours) than in the group of patients with other types of decompression sickness (median 2.0 hours). In both groups, there were different types of recompression tables used for initial treatment and different number of additional sessions of hyperbaric oxygenation (HBO) prescribed, but the final outcome was similar. Complete resolution of symptoms after initial recompression treatment was observed in 24 cases, and this number was increased to 37 cases after additional HBO sessions (from 1 to 20). In the final outcome, some residual symptoms were observed in 12 cases. In 2 cases initial diagnosis of decompression sickness type I was rejected after initial recompression treatment and careful re-evaluation of diving profiles, risk factors and reported symptoms.

[Carbon monoxide pulse oximetry vs direct spectrophotometry for early detection of CO poisoning]. / Porównanie wartosci stezen karboksyhemoglobiny uzyskanych metoda puls-CO-oksymetrii nieinwazyjnej ze spektrofotometrycznym bezposrednim pomiarem we krwi u chorych z podejrzeniem zatrucia tlenkiem wegla.

BACKGROUND: Direct spectrophotometry has been recognized as a standard reference method in the treatment of victims of carbon monoxide (CO) poisoning. Recently, Masimo (USA) has developed a pulse oximeter for the detection of HbCO. Using new probes, similar to those used for traditional pulse oximetry, several different light wavelengths enable detection of different haemoglobins. METHODS: We have compared forty-nine capillary blood samples taken from patients admitted to the hyperbaric center with CO poisoning. The samples were analyzed using direct spectrophotometry (HbCO) and compared with the corresponding pulse CO-oximeter (SpCO) readings. The Bland-Altman method was used for statistical analysis. RESULTS: The mean HbCO concentration was 18.1+/-12.7% (range 0.1% to 47.4%) and the mean SpCO concentration, 17.6+/-11.3% (range 1.0% to 46.0%). There was a strong positive correlation between laboratory results and bedside readings (r2=0.88). The mean difference between readings was 0.5+/-4.3% (range -11.0% to +9.0%), and the distribution was uniform over the whole range of measured levels. For detection of HbCO levels higher than 20%, the sensitivity of the pulse-CO-oximeter was 77.8%, PPV 82.4%, specificity 90.3%, and NPV 87.5%. CONCLUSIONS: Our study confirmed the accuracy of pulse CO-oximetry for rapid detection of the presence and concentration of HbCO. Since this method is based on analysis of peripheral blood flow, it is not clear if it could be used in patients with low perfusion, hypothermia or burns.

[Pneumothorax during hyperbaric oxygenation]. / Odma oplucnowa w trakcie leczenia hiperbarycznego.

BACKGROUND: Tension pneumothorax is an absolute contraindication to hyperbaric oxygenation (HBO). During the decompression, at the end of the hyperbaric session, the increase in gas volume related to decreasing the pressure in the chamber can induce tension pneumothorax. The risk can be minimised, when pleural cavities have been drained before the session. CASE REPORT: A 13-year-old girl was admitted to the Hyperbaric Intensive Therapy Unit after carbon monoxide poisoning and subsequent drowning in a bath and cardiac arrest. She was resuscitated at the site of the accident and transferred to the hyperbaric centre. On admission, she was deeply unconscious, hypothermic, her GCS was 3, and her pupils were non-reacting and maximally dilated. COHb concentration was 48.7%, and X-ray revealed pulmonary oedema. She arrested again and HBO was started during CPR. After 30 min, spontaneous circulation returned and her COHb concentration decreased to 25.6%. During the next 6 h, COHb decreased to 6.5%. The patient developed severe ARDS, and HBO sessions were continued. During the fourth session, the HBO team became aware of an earlier chest x-ray showing a left-sided tension pneumothorax. Emergency decompression was attempted, but it resulted in rapid enlargement of the pneumothorax and deterioration in the patient's condition. The pressure in the chamber was immediately increased and a thoracic drain inserted by the attending anaesthesiologist. Further decompression was uneventful.Despite intensive treatment, the girl died after 85 h of treatment because of severe ARDS. DISCUSSION: Despite initial successful resuscitation, the girl died, primarily due to severe ARDS that was probably related to the near-drowning and repeated CPR. In such cases it is essential to be able to react quickly inside the chamber and an attending anaesthesiologist should be always present in the chamber during HBO sessions.

New Polish occupational health and safety regulations for underwater works.

In Poland, the new regulation of the Ministry of Health on Occupational Health for Underwater Works (dated 2007) pursuant to the Act on Underwater Works (dated 2003) has just been published. It is dedicated for commercial, non-military purposes. It defines health requirements for commercial divers and candidates for divers, medical assessment guide with a list of specific medical tests done on initial and periodical medical examination in order for a diver or a candidate for diver to be recognised fit for work, health surveillance during diving operations, compression and decompression procedures, list of content for medical equipment to be present at any diving place, formal qualifications for physicians conducting medical assessment of divers, requirements for certifications confirming the medical status of divers and candidates for divers. Decompression tables cover divings up to 120 meters of depth using compressed air, oxygen, nitrox and heliox as breathing mixtures. There are also decompression tables for repetitive diving, altitude diving and diving in the high-density waters (mud diving). It this paper, general description of health requirements for divers, as well as decompression tables that are included in the new Regulation on Occupational Health for Underwater Works are presented.

Prognostic factors in sudden sensorineural hearing loss: our experience and a review of the literature.

OBJECTIVES: We investigated prognostic factors in sudden sensorineural hearing loss (SSNHL). METHODS: Our study group consisted of 133 patients with SSNHL who were treated at our department between 1980 and 2000. Eighty-one of them (group B) were treated between 1980 and 1996; they received vasodilators and small doses of steroids. The others (52 patients; group A) were treated between 1997 and 2000; they received vasodilators, steroids at high doses, and hyperbaric oxygen. A multivariate stepwise linear regression was used to identify the prognostic factors that were related to hearing improvement as measured by objective change of gain in the overall average (0.5, 1, 2, 4, 6, 8 kHz), the pure tone average (0.5, 1, 2 kHz), the high tone average (4, 6, 8 kHz), and the pure middle tone average (0.5, 1, 2, 4 kHz). The following factors were included in the analysis: group (method of treatment), age, gender, seasonal occurrence of disease, presence of tinnitus and vestibular symptoms, time delay before first visit, type of initial audiogram, and type of caloric reaction. In group A, an additional analysis was conducted to include the results of certain laboratory tests: blood morphology parameters, erythrocyte sedimentation rate, glucose level, coagulogram, lipidogram, thyroid-stimulating hormone, autoantibodies (antimitochondrial antibodies, smooth muscle antibodies, and anti-brush border antibodies), and immunoglobulins G, A, and M. Values for p of less than .05 were considered significant. RESULTS: Our analysis suggests the presence of the following prognostic factors for SSNHL: method of SSNHL treatment (better results in group A); time delay before the start of treatment (better results when treatment started within 10 days of the first symptoms of SSNHL); and type of caloric reactions (worse results in patients with canal paresis). In group A, the factors for poor prognosis for absolute hearing improvement were as follows: delayed treatment, labyrinth responsiveness disorders, and decreased level of thyroid-stimulating hormone. In group A, better hearing improvement was observed in those patients in whom SSNHL was diagnosed in the spring. CONCLUSIONS: A short time delay before starting treatment (within 10 days), treatment with high doses of steroids and hyperbaric oxygen, preserving complete caloric function of the labyrinths, normal function of the thyroid, and seasonal occurrence of the disease in the spring were positive prognostic factors for hearing recovery in SSNHL.

Hyperbaric oxygen and radiotherapy.

BACKGROUND: Hyperbaric oxygen (HBO) therapy is the inhalation of 100% oxygen at a pressure of at least 1.5 atmospheres absolute (150 kPa). It uses oxygen as a drug by dissolving it in the plasma and delivering it to the tissues independent of hemoglobin. For a variety of organ systems, HBO is known to promote new vessel growth into areas with reduced oxygen tension due to poor vascularity, and therewith promotes wound healing and recovery of radiation-injured tissue. Furthermore, tumors may be sensitized to irradiation by raising intratumoral oxygen tensions. METHOD: A network of hyperbaric facilities exists in Europe, and a number of clinical studies are ongoing. The intergovernmental framework COST B14 action "Hyperbaric Oxygen Therapy" started in 1999. The main goal of the Working Group Oncology is preparation and actual implementation of prospective study protocols in the field of HBO and radiation oncology in Europe. RESULTS: In this paper a short overview on HBO is given and the following randomized clinical studies are presented: a) reirradiation of recurrent squamous cell carcinoma of the head and neck after HBO sensitization; b) role of HBO in enhancing radiosensitivity on glioblastoma multiforme; c) osseointegration in irradiated patients; adjunctive HBO to prevent implant failures; d) the role of HBO in the treatment of late irradiation sequelae in the pelvic region. The two radiosensitization protocols (a, b) allow a time interval between HBO and subsequent irradiation of 10-20 min. CONCLUSION: Recruitment of centers and patients is being strongly encouraged, detailed information is given on www.oxynet.org.

Pneumoperitoneum after diving--two clinical cases and literature review.

Pneumoperitoneum after diving is a rare symptom. Diagnosis and treatment strongly depends on the primary source of the air in the abdominal cavity. There are two main sources of air entering the perineum: perforation of the gastrointestinal tract and pulmonary barotrauma. The management is different and additionally, in both cases, the decompression sickness and arterial gas embolism as consequences of inappropriate decompression phase of the diving should be included in the clinical diagnosis and treatment. The multidisciplinary team including hyperbaric physicians and surgeons is necessary for proper management of such cases. In this paper two cases of pneumoperitoneum of different origins are presented and similar cases reported in the literature are discussed.

[Sudden sensorineural hearing loss: a treatment protocol including glucocorticoids and hyperbaric oxygen therapy]. / Zasady leczenia naglego niedosluchu czuciowo-nerwowego steroidami i tlenem hiperbarycznym na podstawie materialu Kliniki Gdanskiej.

The aim of this study was to evaluate the efficacy of pharmacological treatment (corticosteroids, vasodilators, vitamins, Betaserc) combined with hyperbaric oxygen therapy (HBO) in the sudden sensorineural hearing loss (SSNHL). We reviewed 52 patients with SSNHL treated pharmacologically and with HBO (group A) between 1997 and 2000. All patients in this group received once daily, five days a week, 100% oxygen in a multiplace chamber under pressure of 2.5 ATA for 60 minutes (plus two 5 minutes air breaks). The other group (group B) consisted of 81 patients treated only pharmacologically between 1980 and 1997. Both groups were similar regarding age, season of the year in which deafness occurred, presence of vestibular symptoms and tinnitus, therapeutic delay from initial symptoms to start of treatment, and initial hearing loss, however there were significant differences in gender and shape of hearing loss. The improvement after treatment was measured by tonal audiometry. The retrospective analysis of audiometries performed in all patients was conducted. The improvement of hearing loss was statistically significantly better for group A (vasodilators, high-dose of corticosteroids, vitamins, Betaserc, HBO) than group B (vasodilators, lower-dose of corticosteroids, vitamins) in any single frequency (500-1000-2000-3000-4000-6000-8000 Hz) and in 4 ranges of frequencies (PTA, HTA, PMTA, OAA) both for relative and absolute values. We concluded that the combined therapy of high-dose corticosteroids and HBO improved the clinical results of treatment in the SSNHL, and therefore should be performed in such cases. We also observed that therapeutic delay and flat hearing loss are predictors of poor clinical outcome.

Usefulness of high doses of glucocorticoids and hyperbaric oxygen therapy in sudden sensorineural hearing loss treatment.

OBJECTIVE: We investigated the effect of pharmacologic (steroids, vasodilators, vitamins, and Betaserc) and hyperbaric oxygen therapy on patients with sudden sensorineural hearing loss. METHODS: The pharmacologic arm of the study consisted of 52 patients with defined sudden sensorineural hearing loss treated simultaneously in the ENT Department and National Center for Hyperbaric Medicine of the Medical University of Gdansk, Poland, from 1997 to 2000 (Group A). The hyperbaric oxygen therapy consisted of exposure to 100% oxygen at a pressure of 250 kPa for a total of 60 minutes in a multiplace hyperbaric chamber. The control group included 81 patients with defined sudden sensorineural hearing loss treated in the ENT Department, Medical University of Gdansk, from 1980 to 1996 (Group B). Both groups were comparable regarding the age of the patients, season of hearing loss occurrence, tinnitus and vestibular symptom frequency, delay before therapy, and average threshold loss before the start of treatment. The treatment results (hearing gain) were estimated using pure-tone audiometry. We retrospectively analyzed the audiograms of all patients. RESULTS: Patients from Group A (blood flow-promoting drugs, glucocorticoids in high doses, betahistine, and hyperbaric oxygen therapy) showed significantly better recovery of hearing levels compared with those from Group B (blood flow-promoting drugs and glucocorticoids in low doses) at seven frequencies (500, 1,000, 2,000, 3,000, 4,000, 6,000, and 8,000 Hz) (p < 0.05) and four groups of frequencies (pure-tone average, high-tone average, pure middle-tone average, and overall average) (p < 0.05). Percentage hearing gain in all investigated frequencies was also better in Group A versus Group B, and the differences were statistically significant (p < 0.05). CONCLUSION: We conclude that hyperbaric oxygen therapy with high doses of glucocorticoids improves the results of conventional sudden sensorineural hearing loss treatment and should be recommended. In addition, the best results are achieved if the treatment is started as early as possible.

Delayed treatment of bubble related illness in diving--review of standard protocol.

The basic treatment of diver with bubble related illness consists of recompression in medical hyperbaric facility. However transportation of injured diver to hyperbaric chamber can last for several hours. During that time the process induced by gas bubbles spread out and finally result in activation of many pathophysiological events. Currently approved standard of treatment before starting of recompression consists of normobaric oxygenation, intravenous or oral fluids and general stabilization of the patient condition. Usage of several pharmacological agents is promising, including corticosteroids, antiplatelet and anticoagulant therapy or lidocaine. Those drugs are most often used in some centres but still there is lack of randomized controlled studies concerning their efficacy in decompression illness of divers. The review of available bibliography presented in this paper leads to conclusion that recommendations of the Second European Consensus Conference on Hyperbaric Medicine "The Treatment of Decompression Accidents in Recreational Diving" published in 1996 in Marseille, France for fluid replacement and drug therapy for decompression accidents are still valid. This protocol includes the fluid treatment, normobaric oxygen and intensive therapy. Other drugs (aspirin, lidocaine, heparin, steroids, calcium channel blockers, antioxidants) should still be treated as an option considered by clinician, but without strong evidences from clinical studies.

[Surgical treatment and adjunct hyperbaric therapy to improve healing of wound infection complications after sterno-mediastinitis]. / Leczenie chirurgiczne skojarzone z tlenoterapia hiperbaryczna powiklanego gojenia sie rany z zapaleniem sródpiersia i kosci mostka.

UNLABELLED: Although the incidence of wound complications after median sternotomy is less than 1%, it remains a serious complication in patients undergoing cardiac procedures. We suggest that the combination of hyperbaric oxygen therapy and aggressive surgical approach improves clinical outcomes in these patients. Between August 1997 and May 2002, 55 patients with postoperative sternal wound infection and/or mediastinitis were qualified for hyperbaric oxygen treatment in connection to surgical management. Surgical procedure included wound debridment and/or sternum rewiring, omental pedicle flap plasty or sternectomy. Hyperbaric oxygen therapy consisted of 20 to 40 expositions per patient and was carried before and after the surgery. RESULTS: There was no in-hospital death. The total time between the admission and discharge from the hospital varied from 2 to 24 weeks (average 8 weeks). The infection has been cured in all patients treated for postoperative sternal wound infection. That has been confirmed by negative bacteriological tests, stabilization of the sternum and complete wound healing. CONCLUSIONS: The combination of surgical treatment and hyperbaric oxygen therapy may improve clinical outcome in patients with sterno-mediastinis and poststernotomy wound infection after cardiac surgery.

[An application of hyperbaric oxygen therapy in otolaryngological oncology]. / Zastosowanie hiperbarii tlenowej w onkologii otolaryngologicznej.

Postradiation changes in the tissues and delayed wound healing were presumed by all hyperbaric medicine societies including Undersea and Hyperbaric Medical Society (UHMS) and European Committee for Hyperbaric Medicine (ECHM) as one of the basic indications for hyperbaric oxygen therapy (HBO). The authors estimated the influence of hyperbaric oxygen on molecular, biochemical and cellular changes in injured tissues including that after radiotherapy. Reviewing the references the authors tried to state the actual role of HBO in oncology of head and neck tumors. The authors referred their experiences in adjuvant therapy of head and neck neoplasms with HBO: 1] postradiation changes of head and neck after adjuvant radiotherapy (7 cases) and after primary radiotherapy (1 case); 2] delayed postoperative wound healing (1 case).

The maximum tissue half-time for nitrogen elimination from divers' body.

Both the longest tissue half-time (T1/2max) and the maximum allowable pressure gradient (deltaP) define the safe rate of decompression (DR) after saturation expositions. The mathematical relation between them (DR = -k x deltaP, where: k = ln(2)/(T1/2max)) suggests that experimentally established decompression rate can be hypothetically described by the infinite number of T1/2max and deltaP combinations. The observed number of decompression sickness after saturation decompressions forced to change those parameters subsequently and finally led to values far outside physiological range. Therefore the aim of this study was to compare values of the longest tissue half-time of nitrogen desaturation from diver's body published since 1908 in order to present the evolution of opinions concerning desaturation process. Non-physiological values of T1/2max (from 75 to 1280 minutes) have been published during historical evolution of decompression tables and systems. The currently accepted values of T1/2max (in the range of 320-480 minutes) for saturation and non-saturation air and nitrox divings and hypobaric decompressions, still need to be precised. The discrepancy between T1/2max values obtained using isobaric decompression method and decompressions after diving indicates different physiological phenomena during nitrogen elimination in both methods.

Oxidative stress during oxygen tolerance test.

Reactive oxygen species, including oxygen free radicals are normally generated in human cells during aerobic metabolism. Their production may increase during breathing of hyperoxic mixtures. The 'oxidative stress' has been postulated to be an important contributor to CNS oxygen toxicity. One of the highest partial pressure of oxygen used in healthy humans is 280 kPa(a) during 30 min of 'oxygen tolerance tests' (OTT). This test is conducted in order to detect some individuals with an increased sensitivity to high partial pressures of oxygen leading them to develop CNS oxygen toxicity earlier than others. The purpose of this study was to investigate whether the OTT (30 min of breathing pure oxygen at 280 kPa(a)) would significantly induce oxidative stress in healthy population. The first group consisted of 52 subjects, in whom total antioxidant status (TAS) was measured. The second group consisted of 44 subjects, in whom protein carbonyls (PC), total thiol (t-SH) and heat shock proteins (HSP70) were measured. All measurements were done just before and immediately after the OTT. There was no statistically significant change of TAS. We observed a small, however statistically significant increase of PC and decrease of t-SH. A significant decrease of HSP70 was detected, however false positives of initial measurements are suspected. In summary, in young healthy subjects 30 min of breathing oxygen under pressure of 280 kPa(a) induces oxidative stress which can be detected by increase of protein carbonyls and by decrease of total thiol. In our study this stress was not reflected in measurement of total oxidative status and heat shock proteins.

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.