Hyperbaric Chamber Research Articles

The evaluation of in-chamber sound levels during hyperbaric oxygen applications: Results of 41 centres.

Noise has physical and psychological effects on humans. Recommended exposure limits are exceeded in many hospital settings; however, information about sound levels in hyperbaric oxygen treatment chambers is lacking. This study measured in-chamber sound levels during treatments in Turkish hyperbaric centres. Sound levels were measured using a sound level meter (decibel meter). All chambers were multiplace with similar dimensions and shapes. Eight measurements were performed in each of 41 chambers; three during compression, three during decompression, and two at treatment pressure, one during chamber ventilation (flushing) and one without ventilation. At each measurement a sound sample was collected for 25 seconds and A-weighted equivalent (LAeq) and C-weighted peak (LCpeak) levels were obtained. Recorded values were evaluated in relation to sound level limits in regulations. The highest sound level measured in the study was 100.4 dB(A) at treatment pressure while ventilation was underway and the lowest was 40.5 dB(A) at treatment pressure without ventilation. Most centres had sound levels between 70 dB and 85 dB throughout the treatment. Ventilation caused significant augmentation of noise. The chambers were generally safe in terms of noise exposure. Nevertheless, hyperbaric chambers can be very noisy environments so could pose a risk for noise-related health problems. Therefore, they should be equipped with appropriate noise control systems. Silencers are effective in reducing noise in chambers. Thus far, hyperbaric noise research has focused on chambers used for commercial diving. To our knowledge, this is the first study to investigate noise in hospital-based chambers during medical treatments.

Monoplace chamber treatment of decompression illness: Review and commentary.

This paper summarises the history and capabilities of monoplace chambers in treatment of decompression illness (DCI); both in support of diving operations and in the hospital setting. In the field, monoplace hyperbaric chambers provide victims of DCI immediate access to recompression in settings where traditional multiplace chambers are not available. Alternatively, they may facilitate pressurised transport to a multiplace chamber for continued management. Recently, collapsible lightweight versions have improved suitability for field deployment aboard small vessels in remote settings, and for use by less technically capable military, occupational and civilian operators. The resulting elimination of treatment delays may prove lifesaving and central nervous system sparing, and avoid subsequent diving fitness disqualification. Monoplace chambers thus facilitate diving operations that would otherwise be difficult to condone on health and safety grounds. The 1960s saw the introduction of multiplace hyperbaric chambers into the hospital setting, as a number of non-diving conditions appeared to benefit from hyperbaric oxygen. This coincided with interest in hyperbaric oxygen as a solid tumour radiation sensitiser. Development of a novel acrylic-hulled single occupancy chamber enabled patients to undergo radiotherapy while pressurised within its oxygen atmosphere. Increasing numbers of health care facilities adopted this chamber type as a more economical, less complex alternative to the multiplace chamber. Incorporation of relevant biomedical technologies have allowed monoplace chambers to support increasingly complex patients in a safe, effective manner. Despite these advances, criticism of medical centre-based monoplace chamber treatment of DCI exists. This paper evaluates this controversy and presents relevant counter-arguments.

Eustachian tube function test as a predictor of middle ear barotrauma.

Most of the cases of middle ear barotrauma in divers are due to the impassability of the Eustachian tube. The aim of our study is to compare the results of tympanometry and Valsalva part of Eustachian Tube Function test (ЕТF-test) with the ability of divers to compensate for the change in ambient pressure in a hyperbaric chamber. The study included 35 professional divers undergoing annual medical examination. For all subjects is measured first intratympanal pressure at rest, then after the maneuver of Valsalva with impedancemeter. Then a barofunction test (BFT) was performed to assess the diving fitness and the passability of the Eustachian tubes. It consists of divers compressing and decompressing in a hyperbaric chamber to a pressure of 2.2 ATA for 1 minute. Based on results from previous studies we are using a 20 DaPa cutoff point on the ETF test to predict Eustachian tube passability and a successful barofunction test. In the current study 24 divers have ETF test results higher than 20 DaPa. 3 divers have ETF test values lower than 20 DaPa in both ears, but none of them displayed difficulties in the BFT. 8 divers have ETF values lower than 20 DaPa in one ear and higher than 20 DaPa in the other. 7 of the last group displayed difficulties with the BFT in the ear with poor ETF result. We consider that the ETF test can be used to assess diving fitness as a screening method before performing a BFT, as values above 20 DaPa guarantee Eustachian tube function sufficient for diving activities. Values of 20 DaPa and less are not a definite predictor of the BFT results. The results of the ETF test can also be used in the usual work of an otorhinolaryngologist to evaluate Eustachian function in cases of unilateral disease of middle ear.

Biomarkers of neuronal damage in saturation diving\u2014a controlled observational study

PurposeA prospective and controlled observational study was performed to determine if the central nervous system injury markers glial fibrillary acidic protein (GFAp), neurofilament light (NfL) and tau concentrations changed in response to a saturation dive.MethodsThe intervention group consisted of 14 submariners compressed to 401 kPa in a dry hyperbaric chamber. They remained pressurized for 36 h and were then decompressed over 70 h. A control group of 12 individuals was used. Blood samples were obtained from both groups before, during and after hyperbaric exposure, and from the intervention group after a further 25–26 h.ResultsThere were no statistically significant changes in the concentrations of GFAp, NfL and tau in the intervention group. During hyperbaric exposure, GFAp decreased in the control group (mean/median − 15.1/ − 8.9 pg·mL−1, p < 0.01) and there was a significant difference in absolute change of GFAp and NfL between the groups (17.7 pg·mL−1, p = 0.02 and 2.34 pg·mL−1, p = 0.02, respectively). Albumin decreased in the control group (mean/median − 2.74 g/L/ − 0.95 g/L, p = 0.02), but there was no statistically significant difference in albumin levels between the groups. In the intervention group, haematocrit and mean haemoglobin values were slightly increased after hyperbaric exposure (mean/median 2.3%/1.5%, p = 0.02 and 4.9 g/L, p = 0.06, respectively).ConclusionHyperbaric exposure to 401 kPa for 36 h was not associated with significant increases in GFAp, NfL or tau concentrations. Albumin levels, changes in hydration or diurnal variation were unlikely to have confounded the results. Saturation exposure to 401 kPa seems to be a procedure not harmful to the central nervous system.Trial registrationClinicalTrials.gov NCT03192930.

Hyperbaric oxygen for radiation-induced cystitis: A long-term follow-up

Introduction and objectivesBladder complications may be seen in up to 12% of patients treated with pelvic irradiation. Hyperbaric oxygen therapy (HBOT) is an option for the management of radiation-induced hemorrhagic cystitis (RIHC). The aim of this study was to evaluate the efficacy of HBOT in radiation cystitis and to identify the predictive factors for a successful outcome. Material and MethodsWe retrospectively reviewed 105 patients diagnosed with RIHC which were treated with HBOT between 2007 and 2016 in our institution. Patients received 100% oxygen in a multiplace hyperbaric chamber at 2.4 atm for 80 min. All patients fulfilled a questionnaire documenting symptom severity pre-HBOT and at the end of the follow-up period. ResultsAfter a median of 40 HBOT sessions, there was success rate of 92,4% in the control of hematuria. During our follow-up period (median of 63 months) 24,7% patients presented with recurrence of hematuria. The mean score of the questionnaire-assessed variables: dysuria, urinary frequency and hematuria, was significantly lower after the follow-up period (p < 0,05).Our data shows that the sooner HBOT is delivered after the first episode of hematuria, better response rates are achieved and lower recurrences concerning hematuria were registered (p < 0,05). No serious complications were observed. ConclusionsOur results support the safety and long-term benefits of HBOT on RIHC and other distressful bladder symptoms, which represents an expected improvement of quality of life in our patients

Hyperbaric oxygen-induced long non-coding RNA MALAT1 exosomes suppress MicroRNA-92a expression in a rat model of acute myocardial infarction.

Hyperbaric oxygen (HBO) improves angiogenesis. The effect of HBO on metastasis‐associated lung adenocarcinoma transcript 1 (MALAT1), a pro‐angiogenic long non‐coding RNA, in cardiac myocyte‐derived exosomes and acute myocardial infarction (AMI) is unknown. We aimed to investigate whether MALAT1 is altered in cardiac myocyte‐derived exosomes in response to HBO as well as the molecular regulatory mechanisms of MALAT1 in cardiac myocytes treated with HBO. Cardiac myocytes were cultured, and HBO was applied at 2.5 atmosphere absolute in a hyperbaric chamber. Exosomes were extracted from the culture media. A rat model of AMI generated by the ligation of the left anterior descending artery was used. HBO significantly increased MALAT1 expression in cardiac myocytes and HBO‐induced MALAT1 and exosomes attenuated miR‐92a expression after myocardial infarction. Expression of krüppel‐like factor 2 (KLF2) and CD31 was significantly decreased after infarction and HBO‐induced exosomes significantly reversed the expression. Silencing of MALAT1 using MALAT1‐locked nucleic acid GapmeR significantly attenuated KLF2 and CD31 protein expression after infarction induced by HBO‐induced exosomes. HBO‐induced exosomes also decreased infarct size significantly. HBO‐induced exosomes from cardiac myocytes up‐regulate MALAT1 to suppress miR‐92a expression and counteract the inhibitory effect of miR‐92a on KLF2 and CD31 expression in left ventricular myocardium after myocardial infarction to enhance neovascularization.

Alteraciones oculares en submarinistas: Presentación de 2 casos clínicos y revisión de la literatura

Scuba diving can be practiced recreationally or professionally. In both modalities the diver can be exposed to risks such as decompression syndrome and thus, the use of a hyperbaric chamber, hyper-oxygenation of the gas cylinder, barotrauma, and immersion in closed circuits. These situations have some phenomena in common, such as the great pressure differences, which can cause a wide range of alterations, including ophthalmological ones. The development of index myopia and nuclear cataract are ocular findings frequently associated with increased oxygen pressure. In this context, an imbalance is established between oxidative species and antioxidant defences, such as glutathione, which has a key role in maintaining the transparency of the lens. The cases are presented of 2 young coral fisher patients, who had recently developed a progressive myopisation associated with nuclear cataracts.

Photoplethysmographic Waveform and Pulse Rate Variability Analysis in Hyperbaric Environments.

The main aim of this work is to identify alterations in the morphology of the pulse photoplethysmogram (PPG) signal, due to the exposure of the subjects to a hyperbaric environment. Additionally, their Pulse Rate Variability (PRV) is analysed to characterise the response of their Autonomic Nervous System (ANS). To do that, 28volunteers are introduced into a hyperbaric chamber and five sequential stages with different atmospheric pressures from 1 atm to 5 atm are performed. In this work, nineteen morphological parameters of the PPG signal are analysed: the pulse amplitude; eight parameters related to pulse width; eight parameters related to pulse area; and the two two pulse slopes. Also, classical time and frequency parameters of PRV are computed. Notable widening of the pulses width is observed in the stages analysed. The PPG area increases with pressure, with no significant changes when the initial pressure is recovered. These changes in PPG waveform may be caused by an increase in the systemic vascular resistance as a consequence of of vasoconstriction in the extremities, suggesting a sympathetic activation. However, the PRV results show an augmented parasympathetic activity and a reduction in the parameters that characterise the sympathetic response. So, only a sympathetic activation is detected in the peripheral region, as reflected by PPG morphology. The information regarding the ANS and the cardiovascular response that can be extracted from the PPG signal, as well as its compatibility with wet conditions make this signal the most suitable for studying the physiological response in hyperbaric environments.

Heart rate analysis during very deep dives in flooded caves: single case study

The purpose of this study is to investigate the heart rate adaptations during deep dave diving with MCCR (mechanical closed circuit rebreather). Previous studies on this matter have not been conducted to the depths reached in this study and most of them have been conducted inside hyperbaric chambers trying to recreate the immersion conditions. The data collection took place during the exploration of two hydrogeological sites by a professional cave diver. The recordings were made using a SCUBAPRO GALILEO SOL® dive computer capable of monitoring the heart rate, with a sampling interval of 0,25 Hz. The data collected confirm a direct relationship between the increase in diving depth and the increase in the detected heart rate.

Development of an International, Multicenter, Hyperbaric Oxygen Treatment Registry and Research Consortium: Protocol for Outcome Data Collection and Analysis.

BackgroundHyperbaric oxygen (HBO2)—oxygen at pressures higher than atmospheric—is approved for 14 indications by the Undersea and Hyperbaric Medical Society. HBO2’s main effect is to increase oxygen content in plasma and body tissues, which can counteract hypoxia or ischemia. Laboratory studies show that HBO2 has effects beyond relieving hypoxia (eg, promoting angiogenesis in irradiated tissue, anti-inflammatory effects, radiosensitization of tumors, hypoxia preconditioning, and fungal growth inhibition) and has potential to treat conditions such as inflammatory bowel disease and pyoderma gangrenosum. Lack of consistently collected outcome data on a large cohort of individuals receiving HBO2 therapy limits its use for both established and new indications. A course of therapy often involves 30-40 visits to a hyperbaric chamber, so the number of patients seen at any given center is constrained by chamber capacity. As a result, published HBO2 outcome data tend to be from small case series because few patients with a particular condition are treated at a given center. To solve this problem, a registry that collects and pools data systematically from multiple institutions has been established.ObjectiveThe aim of this study is to collect consistent outcome data across multiple hyperbaric centers to assess treatment effectiveness and establish a research consortium.MethodsA consortium of hyperbaric centers who have agreed to collect consistent outcome data on all patients seen has been assembled. Data are collected at each participating center using Research Electronic Data Capture (REDCap), a web-based, data collection system used frequently for research. Standard outcome measures have been defined for each condition, which are programmed into the REDCap data collection templates. Governance is through a consortium agreement that defines data security, data sharing, publications, liability, and other issues. Centers obtain Institutional Review Board (IRB) and ethics approval to participate, either from their own institutions or by relying on the IRB at the coordinating center at Dartmouth College. Dissemination will occur through a yearly report and by publications based on the data in the registry.ResultsEarly results from some common indications show significant pretreatment to posttreatment changes. Additional indications and outcome measures are being added using the procedures outlined in the consortium agreement.ConclusionsThe registry collects consistent outcome information for a therapy that needs further study and a stronger evidence base. It also overcomes the challenge of collecting data from an adequate number of patients for both established and emerging indications by combining data collection from multiple centers. The data entry requirements should be within the capabilities of existing staff at any given hyperbaric center. By using REDCap, the registry can be expanded to include detailed information on particular indications and long-term follow-up on selected patients without significantly increasing the basic data entry requirements. Through the registry, a network of enrolled hyperbaric centers has been established that provides the basis for a clinical trial network.International Registered Report Identifier (IRRID)DERR1-10.2196/18857

Hyperbaric Oxygenation – Indications and Contraindications

The aim of this work was to conduct a literature review involving the basic concepts of hyperbaric oxygenation, the types of hyperbaric chambers, physiological mechanisms, their indications and contraindications, advantages and disadvantages, volumetric effects, solubility, biochemical and cellular effects; Therapeutic indications and complications associated with hyperbaric oxygenation.

Evaluation of Oxidative Stress in Patients with Difficult-to-Heal Skin Wounds Treated with Hyperbaric Oxygen.

Objective To determine the concentration of thiobarbituric acid reactive substances (TBARS) in erythrocytes and blood plasma, and the activities of selected antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in erythrocytes in patients receiving hyperbaric oxygen (HBO) treatment due to difficult-to-heal “skin wounds”. Material and Methods. Indices of oxidative stress were assessed in venous blood taken from 23 patients three times: immediately before HBO procedure, approx. 5 minutes after leaving the hyperbaric chamber, and after 25 HBO procedures. Moreover, selected blood counts were measured in the collected material two times: prior to treatment and after 25 HBO procedures. Results A statistically significant positive correlation between the CAT activity and the TBARS concentration in the erythrocytes of patients was found before treatment in the hyperbaric chamber (r = 0.394; P ≤ 0.05). No statistically significant changes in the TBARS concentration in erythrocytes and blood plasma were observed both after the first HBO procedure and after 25 procedures. No statistically significant changes in the activities of CAT, SOD, and GPx were noted. Platelet count decreased by 18.7% (P ≤ 0.05) after 25 HBO procedures. Granulocyte count decreased by approx. 21% (P ≤ 0.05), and granulocyte percentage by 11.8% (P ≤ 0.01). In turn, the percentage of lymphocytes and monocytes increased after the treatment by 16.6% (P < 0.05) and 16.4% (P < 0.05), respectively. Conclusions Exposure to HBO due to difficult-to-heal skin wounds does not significantly affect the levels of oxidative stress in the peripheral blood of patients and, from the point of view of oxidation–reduction processes, appears to be a safe therapeutic method for the treatment of chronic wounds.

Oxígeno hiperbárico para la cistitis inducida por radioterapia: un seguimiento a largo plazo

Introduction and objectivesBladder complications may be seen in up to 12% of patients treated with pelvic irradiation. Hyperbaric oxygen therapy (HBOT) is an option for the management of radiation-induced hemorrhagic cystitis (RIHC). The aim of this study was to evaluate the efficacy of HBOT in radiation cystitis and to identify the predictive factors for a successful outcome. Material and methodsWe retrospectively reviewed 105 patients diagnosed with RIHC which were treated with HBOT between 2007 and 2016 in our institution. Patients received 100% oxygen in a multiplace hyperbaric chamber at 2.4atm for 80minutes. All patients fulfilled a questionnaire documenting symptom severity pre-HBOT and at the end of the follow-up period. ResultsAfter a median of 40 HBOT sessions, there was success rate of 92,4% in the control of hematuria. During our follow-up period (median of 63 months) 24,7% patients presented with recurrence of hematuria. The mean score of the questionnaire-assessed variables: dysuria, urinary frequency and hematuria, was significantly lower after the follow-up period (P<.05).Our data shows that the sooner HBOT is delivered after the first episode of hematuria, better response rates are achieved and lower recurrences concerning hematuria were registered (P<.05). No serious complications were observed. ConclusionsOur results support the safety and long-term benefits of HBOT on RIHC and other distressful bladder symptoms, which represents an expected improvement of quality of life in our patients.

Interest of Hyperbaric Oxygen Therapy in Childhood Carbon Monoxide Poisoning: A Retrospective Study

Carbon monoxide poisoning is one of the common causes of poisoning in patients. However, few studies have focused on the pediatric group. We performed this study in order to clarify the clinical characteristics of pediatric patients with Carbon monoxidepoisoning.&#x0D; Methods: We retrospectively reviewed the medical records of pediatric patients (age &lt; 14 years) diagnosed with CO intoxication and admited in the Hyperbaric Oxygen chamber of the military hospital MOHAMED V of RABAT between January 2018 and March 2020, epidemiologic and clinical data were collected, analyzed and compared with literature.&#x0D; Results: A total of 112 children with CO poisoning were identified. Their ages ranged from one to 14 years, symptoms were nausea and vomiting (31%), headache (23%), altred consciousness (19%), dizziness (15%) and seizure (8%). Most events (67.8%) occurred during winter, (100%) of cases were recorded as accidental poisoning. Only one child developed delayed neurologic sequelae, with no death enregistred in our series.&#x0D; The most common cause of intoxication was improperly vented exhaust produced by gas, hot water heaters (98%).(And) (20%) of patients needed two or more sessions of Hyperbaric Oxygen therapy.&#x0D; Conclusion: The treatment of Carbon monoxide poisoning is a race against time. Patients requiringHyperbaric Oxygen therapy must be carefully selected within the first few hours, and kept under close observation. Children with Carbon monoxide poisoning had good outcomes in this series.

Hyperbaric Oxygen Therapy and Vascular Complications in Diabetes Mellitus.

Vascular complications in patients with diabetes mellitus (DM) are common. Since impaired oxygen balance in plasma plays an important role in the pathogenesis of chronic DM-associated complications, the administration of hyperbaric oxygen therapy (HBOT) has been recommended to influence development of vascular complications. Hyperbaric oxygen therapy involves inhalation of 100% oxygen under elevated pressure from 1.6 to 2.8 absolute atmospheres in hyperbaric chambers. Hyperbaric oxygen therapy increases plasma oxygen solubility, contributing to better oxygen diffusion to distant tissues and preservation of the viability of tissues reversibly damaged by atherosclerosis-induced ischemia, along with microcirculation restoration. Hyperbaric oxygen therapy exerts antiatherogenic, antioxidant, and cardioprotective effects by altering the level and composition of plasma fatty acids and also by promoting signal transduction through membranes, which are impaired by hyperglycemia and hypoxia. In addition, HBOT affects molecules involved in the regulation of nitric oxide synthesis and in that way exerts anti-inflammatory and angiogenic effects in patients with DM. In this review, we explore the recent literature related to the effects of HBOT on DM-related vascular complications.

Balloon Dilation of the Eustachian Tube for Baro-Challenge-Induced Otologic Symptoms in Military Divers and Aviators: A Retrospective Analysis.

To evaluate the effectiveness of balloon dilation (tuboplasty) of the Eustachian tube (BET) in active duty military personnel working in hyper- and hypobaric environments suffering from baro-challenge-induced ETD using functional outcomes. Military divers and aviators diagnosed with persistent baro-challenge-induced ETD resulting in disqualification from performing flight and dive duties and who elected for treatment with BET were included for analysis. Posttreatment follow-up assessments were undertaken at 1, 6, and 12 months. Outcome measures included successful hyperbaric chamber testing or return to the hyper- or hypobaric environment without significant baro-challenge-induced ETD symptoms and pre- and postdilation Eustachian Tube Dysfunction Questionnaire (ETDQ-7) scores. Mean pretreatment duration of symptoms was 48 months (range: 3-120 months). Following treatment, 92% (12/13) of patients successfully returned to operational duties with resolution of limiting symptoms. Average return to duty time was 8.5 weeks (range: 6-24 weeks). The ETDQ-7 scores improved from a mean of 4.33 (2.57-6.57) predilation to 2.19 (1.00-4.43) postdilation (Z = 2.73, W = 70, P = .0063). Mean duration of follow-up was 38 weeks (range: 13-70 weeks). Eustachian tube balloon dilation appears to be a safe and highly effective treatment option for baro-challenge-induced ETD in affected military divers and aviators who work in hyper- and hypobaric environments. Further study is needed to determine whether similar results can be achieved in more diverse subject populations and to assess long-term effectiveness.

Underwater hyperbaric dry welding of high strength steel arctic oil and gas pipelines

The paper describes the results of research about orbital hyperbaric FCA-welding of API X70 steel pipes with the use of gas-shielded flux cored wires with the flux of TiO2-CaF2 system with the higher content of fluorides in the flux core. As a result of the research, the dependences of the welding current, arc voltage, metallurgical features and mechanical properties depending the pressure in the hyperbaric chamber are determined. The use of gas-shielded flux cored wires of TiO2-CaF2 system within the gas pressure 0,1–0,6 MPa, for the orbital welding of API X70 steel provides the favourable microstructure of welded joint and mechanical properties of welds according to the Class A per ANSI/AWS D3.6M:2010.

Pupillometry is not sensitive to gas narcosis in divers breathing hyperbaric air or normobaric nitrous oxide.

Gas narcosis impairs divers when diving deeper. Pupillometry is sensitive to alcohol intoxication and it has been used in anaesthesia to assess nitrous oxide narcosis. It is a potential novel method to quantify narcosis in diving. The aim of this study was to evaluate pupillometry for objective measurement of narcosis during exposure to hyperbaric air or nitrous oxide. Pupil size in 16 subjects was recorded directly at surface pressure and during air breathing at 608 kPa (equivalent to 50 metres' seawater depth) in a hyperbaric chamber. Another 12 subjects were exposed to nitrous oxide at end-tidal percentages of 20, 30 and 40% in random order at surface pressure. Pupil size and pupil light reflex were recorded at baseline and at each level of nitrous oxide exposure. Pupil size did not significantly change during exposure to hyperbaric air or nitrous oxide. The pupil light reflex, evaluated using percentage constriction and minimum diameter after exposure to a light stimulus, was affected significantly only during the highest nitrous oxide exposure - an end-tidal level of 40%. Pupillometry is insensitive to the narcotic effect of air at 608 kPa in the dry hyperbaric environment and to the effects of low dose nitrous oxide. Pupillometry is not suitable as a monitoring method for gas narcosis in diving.

Carotid body chemosensitivity at 1.6 ATA breathing air versus 100% oxygen.

Hyperoxia reduces the ventilatory response to hypercapnia by suppressing carotid body (CB) activation. This effect may contribute to CO2 retention during underwater diving due to the high arterial O2 content associated with hyperbaria. We tested the hypothesis that CB chemosensitivity to hypercapnia and hypoxia is attenuated during hyperbaria. Ten subjects completed two, 4-h dry dives at 1.6 atmosphere absolute (ATA) breathing either 21% O2 (Air) or 100% O2 (100% O2). CB chemosensitivity was assessed using brief hypercapnic ventilatory response ([Formula: see text]) and hypoxic ventilatory response ([Formula: see text]) tests predive, 75 and 155 min into the dives, and 15 and 55 min postdive. End-tidal CO2 pressure increased during the dive at 75 and 155 min [Air: +9 (SD 4) mmHg and +8 (SD 4) mmHg versus 100% O2: +6 (SD 4) mmHg and +5 (SD 3) mmHg; all P < 0.01] and was higher while breathing Air (P < 0.01). [Formula: see text] was unchanged during the dive (P = 0.73) and was not different between conditions (P = 0.47). However, [Formula: see text] was attenuated from predive during the dive at 155 min breathing Air [-0.035 (SD 0.037) L·min·mmHg-1; P = 0.02] and at both time points while breathing 100% O2 [-0.035 (SD 0.052) L·min·mmHg-1 and -0.034 (SD 0.064) L·min·mmHg-1; P = 0.02 and P = 0.02, respectively]. These data indicate that the CB chemoreceptors do not appear to contribute to CO2 retention in hyperbaria.NEW & NOTEWORTHY We demonstrate that carotid body chemosensitivity to brief exposures of hypercapnia was unchanged during a 4-h dive in a dry hyperbaric chamber at 1.6 ATA regardless of breathing gas condition [i.e., air (21% O2) versus 100% oxygen]. Therefore, it appears that an attenuation of carotid body chemosensitivity to hypercapnia does not contribute to CO2 retention in hyperbaria.

Efficacy of UV-C disinfection in hyperbaric chambers.

Ultraviolet C (UV-C) light reduces contamination on high-touch clinical surfaces. We assessed the efficacy of 2 UV-C devices at eradicating important clinical pathogens in hyperbaric chambers. Both devices were similarly efficacious against MRSA but differed significantly against C. difficile. Additionally, direct UV-C exposure was more efficacious against both species than indirect exposure.