Hyperbaric Chamber Research Articles

Abstract TP414: Symptomatic Cerebral Air Embolus and the Challenge of Staff Education and Access to Therapy

Background: Cerebral Air Embolus (CAE) is a rare condition and recognition can be difficult. We identified 6 cases of symptomatic cerebral air embolus (SCAE) in patients undergoing procedures or admitted for reasons besides stroke. Our hospital is a 750 bed comprehensive stroke center with a 24/7 Rapid Response Team (RRT) that responds to emergent in house situations that require both manpower and expertise. Purpose: The purpose of this project is to define gaps in knowledge of SCAE and determine if education of the RRT can bridge the gap in early identification and intervention of rare stroke syndrome with high morbidity. Methods: We reviewed the characteristics of the SCAE patients including location in the hospital, related procedure, clinical syndrome and involvement of the RRT. Emergency interventions considered or carried out were reviewed. We tested the members of the RRT on knowledge of CAE before and after an education module. Results: SCAE presented in several areas of the hospital including endoscopy, interventional radiology, and general medical units. Sudden change in awareness with left hemiplegia after a procedure was a common clinical presentation. Cerebral imaging studies were often inconclusive or negative. Patient positioning, hydration status, oxygen use and consideration of hyperbaric therapy were irregularly documented and 50% of the cases died or had profound impairment. Access to hyperbaric chambers in a timely manner was noted to be a gap. We determined that the number of staff potentially witnessing a CAE was 2,494 RNs including all medical units, but higher likelihood was in endoscopy/interventional radiology (38 RNs). RRT was the most commonly involved group of bedside nurses (11 RNs). Overall RRT scores on CAE facts improved from 45% to 95% after an educational module. Conclusions: SCAE is a rare event with high morbidity that can occur in many areas of the hospital. Hyperbaric therapy, though widely available, can be difficult to initiate on an emergent basis. Education of the RRT is the most efficient way to ensure an available pool of expertise.

How Expertise Changes Cortical Sources of EEG Rhythms and Functional Connectivity in Divers Under Simulated Deep-Sea Conditions.

Although the recent years have witnessed a growing interest in functional connectivity (FC) through brain sources, the FC in extreme situations has not been completely elucidated. This paper is aimed at investigating whether the expertise acquired during the deep-sea diving is reflected in FC in a group of professional divers (PDs) compared to a group of new divers (NDs), and how it could affect the concentration and stress levels. The sources of brain frequency rhythms, derived by the electroencephalography acquisition in a hyperbaric chamber, were extracted in different frequency bands and the corresponding FC was estimated in order to compare the two groups. The results highlighted a significant decrease of the alpha source in PDs during air breathing and a significant increase of the upper beta source over central areas at the beginning of post-oxygen air, as well as an increase of beta FC between fronto-temporal regions in the last minutes of oxygen breathing and in the early minutes of post-oxygen air. This provides evidence in support of the hypothesis that experience and expertise differences would modulate brain networks. These experiments provided the unique opportunity of investigating the impact of the neurophysiological activity in simulated critical scenarios in view of the investigation in real sea-water experiments.

Experimental hyperbaric chamber trials reveal high resilience to barotrauma in Australian snapper (Chrysophrys auratus)

A key factor affecting survival of fish which are captured at depth and subsequently released is barotrauma. Barotrauma are a suite of injuries which occur as a result of the decreasing ambient pressure experienced by a fish during capture and are caused by expanding swim bladder gas and formation of gas embolisms. Snapper (Chrysophrys auratus) are of key importance to both commercial and recreational fisheries in southern Australia and are often released after capture suffering from barotrauma. Previous research has yielded inconsistent results for survival of C. auratus after suffering barotrauma, in part due to influences related to capture, ‘cage’ effects and the use of only very short term post-catch and release monitoring. This study therefore used laboratory hyperbaric chambers to simulate the pressure changes associated with capture to investigate whether barotrauma was a direct cause of mortality in C. auratus. The influences of depth and repressurization on mortality, behaviour and symptoms due to barotrauma could therefore be examined in a controlled environment independent of capture and ‘cage’ effects combined with long-term monitoring (220 d) post-simulation. In a pilot experiment C. auratus (n = 12) were depressurized from 8 bar (≈70 m depth), before being repressurized after 2 min at 1 bar (atmospheric pressure) resulting in agitated in-chamber behaviours and abdominal distension as a result of swim bladder perforation, but 100% survival. A second experiment depressurized C. auratus from 4 bar (≈30 m depth); one treatment group (n = 32) were repressurized after 10 min again resulting in behaviour and symptoms indicative of swim bladder perforation and 100% survival, the other group (n = 32) was left at 1 bar and exhibited many additional external and internal barotrauma symptoms and suffered 16% mortality. Despite the death of a single control individual, statistical analyses found a significant effect of treatment on mortality. Mortality occurred within 15 min of depressurization and the cause of death was consistent with the formation of gas embolisms. Staged post-mortems performed on C. auratus that had been depressurized from 4 bar to induce swim bladder perforation indicated that swim bladders were healed sufficiently to hold gas after just 2 d. C. auratus were shown to be a remarkably robust species to the effects of barotrauma, particularly if repressurized quickly (<10 min) after capture and this resilience is likely reflective of their characteristic semi-pelagic physiology. This study also demonstrated the usefulness of laboratory hyperbaric chambers to examine the long term (>200 d) effects of depressurization on deep water fish species independent of capture and ‘cage’ effects.

The Effect of a 300 mBar Increase in Barometric Pressure on Digital Microcirculation in Healthy Subjects Exposed to High Altitude: Is the Use of a Portable Hyperbaric Chamber to Treat Frostbite and/or Hypothermia in the Field Indicated? (Flow_Pulse Study).

Hypothermia and frostbite occur when there is a significant decrease in central and peripheral body temperature in individuals exposed to cold windy conditions, often at high altitude or in a mountain environment. Portable hyperbaric chambers increase the barometric pressure and thereby the partial pressure of oxygen inside the chamber, and their use is a well-known treatment for altitude illness. This study aims to show that a portable hyperbaric chamber could also be used to treat hypothermia and frostbite in the field, when rescue or descent is impossible or delayed. During a European research program (SOS-MAM, Flow Pulse study) measurements were taken from 27 healthy nonacclimatized voluntary subjects (21 men, 6 women, mean age 41 ± 17) at an altitude of 3800 m (Chamonix Mountain Lab, Aiguille du Midi, France) right before and immediately after spending 1 hour in a portable hyperbaric chamber at 300 mbar. We measured digital cutaneous temperature (Tcut), digital cutaneous blood flow (Fcut), digital tissue oxygenation (TcPO2), blood oxygen saturation (SpO2), heart rate, and core temperature. Air temperature inside the chamber (Tchamb) was measured throughout the whole session. We observed significant increases in Tchamb: 9.3°C compared with the outside temperature, Tcut: +7.5°C (±6.2°C 71%), Fcut: +58PU (±89) (+379%), TcPO2: +18 mmHg (±11.9) (304%), and SpO2: 13%. This study shows that a portable hyperbaric chamber can be used to treat frostbite and/or hypothermia in the field at altitude when descent or rescue is impossible or even simply delayed.

Noise Prevention Research in the Hyperbaric Oxygen Chamber by Flux Vector Splitting Format

This paper describes the application of computational fluid dynamics(CFD) in noise prevention of hyperbaric oxygen chambers. The flux vector splitting format and matrix transformation are used in the calculation of flow field in the hyperbaric oxygen chamber. At first, this paper simplifies the model of the hyperbaric oxygen chamber, and calculates the conservative state equation by flux vector splitting format. Being auxiliary to initial conditions, boundary conditions, meshing, time steps, and other computing elements, this paper gets the transient distribution of the parameters of each time step from flowing start to its near stop. Through displaying the data by graphic, we get the flow velocity variation, the location of the shock wave, the variational trend of pressure, and the variational trend of temperature. This paper compares the numerical and experimental results. Their similarity degree is high and this proves the feasibility to design Low-noise hyperbaric oxygen chamber by this numerical calculation method.

Proof of concept study using a modified Politzer inflation device as a rescue modality for treating Eustachian tube dysfunction during hyperbaric oxygen treatment in a multiplace (Class A) chamber

Eustachian tube dysfunction (ETD) and middle ear barotrauma (MEB) are the most common adverse effects of hyperbaric oxygen (HBO2) treatments. Patients practice equalization maneuvers to prevent ETD and MEB prior to hyperbaric exposure. Some patients are still unable to equalize middle ear pressure. This ETD results in undesirable consequences, including barotrauma, treatment with medications or surgical myringotomy with tube placement and interruption of HBO2. When additional medications and myringotomy are employed, they are associated with additional complications. A device known as the Ear Popper® has been reported to reduce complications from serous otitis media and reduce the need for surgical interventions (myringotomy). Patients unable to equalize middle ear pressure during initial compression in the hyperbaric chamber were allowed to use the device for rescue. All hyperbaric treatments were compressed using a United States Navy TT9, or a 45-fsw hyperbaric treatment schedule. Patients with persistent ETD and the inability to equalize middle ear pressure were given the Ear Popper upon consideration of terminating their treatment. The Ear Popper allowed all patients to successfully equalize middle ear pressure and complete their treatments. This study substantiates the use of this device to assist in allowing pressurization of the middle ear space in patients otherwise unable to achieve equalization of middle ear pressure during HBO2 treatment in a multiplace chamber.

Modelling of the Nnormobaric and Hyperbaric Facilities Ventilation

This paper is the result of many work and research programs. During the execution of the projects, it was proposed a new mathematical model of the process of ventilation of a semi-closed rebreather. Its validation required making a special simulator of gas exchange in the breathing process. Use of the device made experimental validation of the proposed model possible. This model has been adjusted to the process of ventilation in hyperbaric chambers. The validation process required developing a new type of carbon dioxide emission simulator. The generalization of the adopted method for the submarine ventilation process was only an obvious consequence of earlier considerations. However, the validation process required to undertake extensive research on a real object, which confirmed the validity of the modelling method adopted. The research on ventilation of the mining excavation constituted the validation of the adopted research approach. In typical residential and public buildings, similar methods have been used relatively recently. In general, they involve air-conditioning of the sealed buildings. This entails the need to regenerate the respiratory atmosphere inside, making them similar to military facilities. Methods of protection against contamination can be used with regard to atmospheric pollution, especially in the work environment. As in the case of military facilities, the methods of modelling ventilation in standard and hyperbaric objects described here would allow developing more accurate methods to design and use ventilation and air-conditioning systems in buildings.

Influence of Deep-Sea Ambient Conditions in the Performance of Pressure-Compensated Induction Motors

AbstractUnderstanding the influence of low temperature and high hydrostatic pressure in the starting performance of deep-sea pressure-compensated (PC) induction motors is essential for sizing of the motor and upstream power systems. This paper presents the observations from experiments carried out on industry-standard 3000-V rated deep-sea PC induction motors of 30- and 60-kW capacities in a hyperbaric chamber. It is identified that the motors consume about 30% of their rated power when started at a pressure of 600 bar and a temperature of 2°C. The results could be used for sizing of deep sea electric motors taking into consideration the increased starting power requirements due to the viscous drag of the PC fluid and to design PC oil viscosity management systems.

"Airplane ear"-A neglected yet preventable problem.

Airplane ear or ear discomfort during flight is common irrespective of ticket price we pay for our flights according to class. Whether we get extra leg space or extra facilities during flying in business class, air travelers often face this problem of airplane ear (Figure 1). Airplane ear is also known as ear barotrauma, barotitis media or aerotitis media [1]–[5]. Severe earache affects individuals of varying levels of social determinants of health as it is entirely a physiological phenomenon [3]. Airplane ear is commonly experienced when the airplane is ascending or descending, which makes it one of the commonest health problems for people travelling in air routes. Open in a separate window Figure 1. Airplane ear. 2. Etiology Generally, airplane ear occurs due to quick changes in altitude and quick changes in air pressure [4]. In normal physiological conditions, the air pressure in our middle ear cavity is nearly equivalent to that of the external ear canal. This equalization of air pressure is maintained physiologically and contributes to regular auditory function and maintenance of normal balance among individuals. However, the eustachian tube dysfunction may occur with any changes in pressure and failure to ventilate through the middle ear space. This may result in outward bulging of the tympanic membrane causing moderate to severe earache. This phenomenon can be compared with a bread expanding while baking [3],[5]. Conversely, due to the vacuum effect, if the air pressure inside the middle ear space reduces rapidly compared to the external ear pressure, the tympanic membrane may be pulled inside due to the pressure gradient. The eustachian tube becomes flattened during the pressure changes and it necessitates bringing air into the middle ear (Figure 2). During sudden ascend or descend of an aeroplane, ear cavity pressure is often decreased complemented by an increase in the cabin compared to the outside air pressure. In such a scenario, the unusual stretching of the eardrum or tympanic membrane may precipitate pain in the ear. At the same time, individuals may also experience decreased hearing abilities and muffled sounds as the eardrum as it becomes unable to vibrate normally [2]–[4]. Open in a separate window Figure 2. Imbalance of air pressure in the middle ear. The pathophysiology remains the same in cases of scuba diving, in hyperbaric oxygen chambers, and during explosions happening nearby [2].

Efekat hiperbarične oksigenoterapije na kvalitet života i stanje mikrocirkulacije kod bolesnika sa sistemskom sklerozom

Introduction: Systemic sclerosis (SSC) is a rare, chronic, progressive, severe illness with unknown etiology and characteristics of impaired microcirculation. The effect of hyperbaric oxygen therapy (HBOT) is reflected in the efficiency of pure oxygen under pressure greater than atmospheric and it is main indication for the application in the state of disturbed microcirculation. Aim: The aim was to examine the effect of HBOT on the quality of life and the state of microcirculation in patients with SSc. Material and methods: The research represents retrospective study which involved 18 female patients with SSc. All patients completed the HAQ, SySQ and TIFS questionnaires and all basic laboratory analyzes, as well as total anti-nuclear antibodies (ANA), anti-centromer antibodies (ACA), and anti-topoisomerase-1 antibodies (Anti-Scl-70). Rodnan skin score, capillaroscopy, and diffusion spirometry were made and values of forced vital capacity (FVC) and lung diffusion capacity for carbon monoxide (DLco) were taken. Results: FVC values were 96.61 ± 13.44 (78 - 122) before departure, but after treatment they were 115.94 ± 16.69 (82 - 135). DLco values were 73.61 ± 6.63 before departure, after departure results were 87.33 ± 9.30. ANA antibodies were positive in 38.9%, ACA were positive in 22.2%, and Anti-Scl-70 were positive in 16.7%. The mean value of ESR was 20.5 (4 - 42) before going to the hyperbaric chamber, and after departure it was 12 (3 - 27). Conclusion: Our research has shown that HBOT has a significant effect on patients with SSc, but further research is needed to determine the exact effect of HBOT on this disease.

Influence of supportive psychotherapy toward patient anxiety to pre-hyperbaric therapy

The used of Hyperbaric therapy at Port Health Center of West Nusa Tenggara keeps increasing.There were fifteen patients with thirty-six times of visit during 2011. Meanwhile, there were twelve type of cases in which forty-two pateints came eighty-one times in 2012. However, this therapy also meets an annulment due to psychological condition such patients’ anxiety. There were three cases found in 2011 whereas five patients could not perform this therapy in 2012. The annulment of therapy caused by a fear and anxiety factors. This information was obtained from patients. Moreover, according to Port Health Center of West Nusa Tenggara in 2012 reported “physical assessment that is conducted indicated the incresing of blood pressure, pulse rate frequency, and excessive of sweat. The objective was to find out the influence of supportive psychotherapy toward patients’ anxiety against pre-hyperbaric therapy at Port Health Center. The research was done at Hyperbaric therapy chamber in July to November 2012. The research design employed pre and post test.

Hyperbaric oxygen therapy for postoperative ischemic bronchitis after resection of lung cancer.

Hyperbaric oxygen therapy (HBOT) has been used successfully in the treatment of specific ischemic injuries, but has been a little evaluated specifically in postoperative ischemic bronchitis (POIB). The purpose of this study was to evaluate the effect of HBOT when used for POIB after resection of lung cancer. From January 1999 to December 2016, 1,100 patients underwent lymph node dissection (LND) and either anatomic pulmonary resection or lung resection with bronchoplasty for lung cancer. POIB was diagnosed by bronchoscopy. HBOT was administered after POIB was diagnosed. HBOT comprised one 60-minute session daily in the hyperbaric chamber at 2.0 absolute atmospheres with 100% oxygen. We retrospectively analyzed the clinical course, timing of onset of POIB, outcomes, and any adverse events. Seven patients were identified to have had POIB treated with HBOT, all of whom were men with a smoking history and a median age of 65 years (range, 57-72 years). The operative procedures included three lung resections with bronchoplasty, three right lower lobectomies, and one right middle lobectomy performed owing to torsion of the middle lobe after right upper sleeve lobectomy. All 7 patients underwent subcarinal LND. POIB was diagnosed at a median of 11 days (range, 4-41 days) postoperatively. The median duration of an HBOT session was 7 days (range, 3-11 days). POIB resolved in 5 patients but worsened in 2, both of whom required further surgery. Prospective clinical trials are now needed to confirm the potential benefits of HBOT in POIB.

Risk of continuous bladder irrigation in the monoplace hyperbaric chamber: a cautionary tale

We previously published our method of performing continuous bladder irrigation (CBI) in a monoplace hyperbaric chamber [1]. This method entailed the use of an IV pump to infuse saline into the monoplace chamber. The specter of causing iatrogenic rupture of the bladder was raised following such a case, reported herein, of a woman with hemorrhagic radiation cystitis leading to cystectomy. Due to the danger of bladder rupture while providing CBI with a pump, we retract ourpreviously reported method and encourage the use of either a gravity-fed system or delay in hyperbaric oxygen therapy treatment until CBI is no longer necessary.

Hyperbaric oxygen boosts long noncoding RNA MALAT1 exosome secretion to suppress microRNA-92a expression in therapeutic angiogenesis

BackgroundHyperbaric oxygen (HBO) could improve wound healing by enhancement of angiogenesis. The effect of HBO on metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a proangiogenic long noncoding RNA, and on endothelial cell-derived exosome is unknown. We aim to investigate both whether MALAT1 is altered in human coronary artery endothelial cells (HCAECs)-derived exosomes in response to HBO as well as the molecular regulatory mechanisms of MALAT1 in HCAECs under HBO treatment. Methods and resultsHCAECs were cultured and HBO was applied at 2.5 atmosphere absolute (ATA) in a hyperbaric chamber. Exosomes were extracted from culture media. A rat model of hind-limb ischemia was performed by ligation of the right femoral artery. HBO at 2.5 ATA significantly increased MALAT1 expression in HCAECs and HCAECs-derived exosomes. MALAT1 suppressed miR-92a expression in HCAEC-derived exosomes under HBO. Silencing MALAT1 by MALAT1 siRNA significantly inhibited KLF2 mRNA expression induced by HBO, as did MiR-92a. MiR-92a significantly decreased KLF2 luciferase activity in HCAECs under HBO. HBO and HBO-induced exosomes significantly increased cell proliferation and the capillary-like network formation of HCAECs. MALAT1 siRNA and miR-92a overexpression significantly attenuated the cell proliferation and tube formation caused by HBO-induced exosome. HBO and HBO-induced exosomes significantly improved neovascularization in a rat model of hind-limb ischemia. ConclusionsHBO upregulates MALAT1 to suppress miR-92a expression and counteracts the inhibitory effect of miR-92a on KLF2 expression in HCAECs to enhance neovascularization. HBO-induced derivation of exosomes from HCAECs enhances angiogenesis. Exosomes containing MALAT1 might serve as a valuable therapeutic tool for neovascularization by HBO.

Pulmonary effects of repeated six-hour normoxic and hyperoxic dives.

This study examines differential effects of immersion, elevated oxygen partial pressure, and exercise on pulmonary function after series of five daily six-hour dives at 130 kPa (1.3 ATA), with 18 hours between dives. Five cohorts of 10 to 14 divers participated. The exposure phases were resting while breathing O2 or air in the water (“wetO2”, “wetAir”) or O2 in the hyperbaric chamber (“dryO2”), and exercise in the water while breathing O2 or air (“wetO2X”, “wetAirX”). Respiratory symptoms were recorded during and after each dive, and pulmonary function (forced flow-volume) was measured twice at baseline before diving, after each dive both immediately and on the following morning, and three days post diving (“Day+3”). The incidences of symptoms and of flow volume changes from baseline greater than normal limits (“ΔFV”) were assessed, as were mean ΔFV. The parameters examined were forced vital capacity (FVC), forced expired volume in 1 second (FEV1), and forced expired flow from 25% to 75% volume expired (FEF25–75). The phases ranked from greatest to least fraction of diver-days with symptoms were wetO2X (56%) > dryO2 (42%) > wetO2 (13%) > [wetAir (2%) or wetAirX (1%)] (p<0.05). FEV1 and FEF25–75 were depressed in the morning following wetO2 and wetO2X and on Day+3 after and wetO2X, but increased immediately following each wetAirX dive. O2 exposures caused symptoms and ΔFV suggestive of pulmonary oxygen toxicity,exacerbated by exercise. Indices of small airway function showed late (17-hour) post-O2 exposure deficits, but, particularly with exercise, improvement was evident early after exposure with or without O2. FEF25–75 and FEV1 remained depressed on Day+3 after wetO2 and wetO2X.

Pressure-Tolerant Electronics and Discharge Performance of Pressure-Compensated Lead Acid Batteries Under Hyperbaric Conditions

AbstractUnderstanding the variations in the energy discharge performance of pressure-compensated valve-regulated lead acid (PC VRLA) batteries under the influence of increased hydrostatic pressure is essential for the reliable design of deep-ocean battery-powered systems. The paper reviews developments in the field of pressure-tolerant electronics and presents observations from the experiments done on a12 V‐40 Ah absorbent glass mat type PC VRLA battery in a hyperbaric chamber at 600 bar pressure. It is identified that, during discharge at 600 bar pressure, the terminal voltage and energy discharge capacity of a 12-V fully charged battery drop by 1.05 V and about 15%, respectively, and need to be discharged below the minimum voltage levels recommended under normal ambient conditions. The identified results, along with the temperature derating factor, could be used for sizing of deep-ocean operated PC VRLA batteries.

Hyperbaric oxygenation on adhesions prevention after laparotomy in rats.

To evaluate the effects of hyperbaric oxygenation on prevention of adhesions in the abdominal cavity after laparotomy. Fifty four rats underwent laparotomy; stitches were made in the four quadrant parietal peritoneum and abdominal cavity closure. Animals were divided into three groups: 1 - control; 2 - subjected to high pressures and oxygenation; 3 - subjected to 100% hyperbaric oxygenation. The animals in groups 2 and 3 were daily submitted to oxygenation hyperbaric chamber after surgery. On the seventh day another laparotomy, registration of procedure, assessment of adhesions and biopsies of the peritoneum were held. Professionals analyzed the videos and the biopsies. Peritoneal cavity adhesions occurred in animals of three groups with no difference between them. In Group 3, the adhesions presented more fragile and vascular proliferation more pronounced, and there was no difference in comparison with the first and second groups. However, there was no significant difference in the evaluation of these parameters between the animals in groups 1 and 2. Postoperative hyperbaric oxygenation in rats submitted to laparotomy did not alter the frequency, but reduced the density of adhesions in the peritoneal cavity and promoted vascular proliferation. The change in atmospheric pressure alone had no influence on the results.

A Hyperbaric Warm Perfusion System Preserves Tissue Composites Ex vivo and Delays the Onset of Acute Rejection.

Ischemia-reperfusion injury (IRI) precipitates acute rejection of vascularized composite allografts (VCA). Hyperbaric preservation of tissues ex vivo, between harvest and revascularization, may reduce IRI and mitigate acute rejection of VCA. A porcine heterotopic musculocutaneous gracilis flap model was used. In phase 1, control autografts (n = 5) were infused with University of Wisconsin Solution (UWS) and stored at 4°C for 3 hours. Intervention autografts (n = 5) were placed in a hyperbaric oxygen organ preservation system for 5 hours and infused with hyperoxygenated UWS at 20°C and 3 atm. Grafts were replanted into the animals' necks. In phase 2, similarly treated control (n = 8) and intervention grafts (n = 8) were allotransplanted into the necks of animals separated by a typed and standardized genetic mismatch. No systemic immunosuppression was given. Systemic markers of IRI, and clinical and histopathological assessments of necrosis and rejection were performed. Autotransplanted tissue composites preserved in the hyperbaric chamber showed histopathological evidence of less muscle necrosis at 3 hours (p = 0.05). Despite a longer period of ischemia, no evidence was found of a difference in systemic markers of IRI following revascularization in these groups. Allotransplanted tissues supported ex vivo within the hyperbaric perfusion device experienced acute rejection significantly later than corresponding controls. Hyperbaric warm perfusion preserves musculocutaneous tissue composites ex vivo for longer than standard cold preservation in this model. This translates into a delay in acute rejection of allotransplanted tissue composites.

Identification and control of a multiplace hyperbaric chamber.

This work presents the automation of a multiplace hyperbaric chamber. It includes the system modeling, identification, controller calculation and system validation. With the proposed approach a good pressure profile tracking and repeatability are achieved. Moreover, the proposed automation includes the implementation of powerful treatment tools such as Pause and Alleviation procedures. The control system implemented is based on a special zero-pole cancellation regulator. Experimental results are provided to illustrate the behavior of the automated chamber. It is important to remark that the chamber automated in this work is being successfully used in a real hospital since 2015 treating more than 40 patients per day, five days a week.

An experimental and numerical study on inward integral buckle arrestors for pipe-in-pipe systems

ABSTRACTA type of improved device, designated as inward integral buckle arrestor, is introduced for the pipe-in-pipe (PIP) systems. The experiments have been performed to reproduce the buckle propagation and crossover scenarios of the PIP installed with such devices in a hyperbaric chamber under external pressure. Based upon the experimental observations, dedicated finite element models for test specimens are developed to simulate the whole process of a propagating buckle crossing over an inward integral arrestor to the downstream PIP under the quasi-static, steady-state conditions. Through extensive parametric dependence analyses, the potential buckle propagation and crossover modes are identified, and a reasonable empirical formula of the crossover pressure of the arrestors for the PIP systems is established. The corresponding empirical design formula and lower bound envelope line are proposed to estimate the arresting efficiency of such devices in the preliminary design stage.