Decompression sickness with incidental pulmonary cyst.

Decompression sickness (DCS) is a known complication of scuba diving. DCS occurs when bubbles are formed as pressure is reduced during and after ascent from a dive, following inert gas uptake during the dive. The bubbles cause inflammation and hypoxia. The definitive treatment for decompression sickness is hyperbaric oxygen therapy. We present a case of a healthy 16-year-old male who presented with decompression sickness and an incidental pulmonary cyst discovered by chest CT, likely congenital. The patient was successfully treated with U.S. Navy Treatment Table 6 (TT6) for his decompression sickness, but he continued to have chest pain, requiring hospitalization and consultation with pediatric pulmonology and cardiothoracic surgery from the cyst. Three years later he complained of chest pain with changes in altitude. Chest CT showed persistence of this cyst, and additional cysts. Case conference with pulmonologists and chest radiologist could not offer a definite etiology without lung biopsy, felt to not be indicated. We believe that the changes in pressure/volumes during the dives and TT6 exacerbated his pulmonary cyst.

Physiologic and biochemical rationale for treating COVID-19 patients with hyperbaric oxygen.

The SARS-Cov-2 (COVID-19) pandemic remains a major worldwide public health issue. Initially, improved supportive and anti-inflammatory intervention, often employing known drugs or technologies, provided measurable improvement in management. We have recently seen advances in specific therapeutic interventions and in vaccines. Nevertheless, it will be months before most of the world's population can be vaccinated to achieve herd immunity. In the interim, hyperbaric oxygen (HBO2) treatment offers several potentially beneficial therapeutic effects. Three small published series, one with a propensity-score-matched control group, have demonstrated safety and initial efficacy. Additional anecdotal reports are consistent with these publications. HBO2 delivers oxygen in extreme conditions of hypoxemia and tissue hypoxia, even in the presence of lung pathology. It provides anti-inflammatory and anti-proinflammatory effects likely to ameliorate the overexuberant immune response common to COVID-19. Unlike steroids, it exerts these effects without immune suppression. One study suggests HBO2 may reduce the hypercoagulability seen in COVID patients. Also, hyperbaric oxygen offers a likely successful intervention to address the oxygen debt expected to arise from a prolonged period of hypoxemia and tissue hypoxia. To date, 11 studies designed to investigate the impact of HBO2 on patients infected with SARS-Cov-2 have been posted on clinicaltrials.gov. This paper describes the promising physiologic and biochemical effects of hyperbaric oxygen in COVID-19 and potentially in other disorders with similar pathologic mechanisms.

Hyperbaric oxygen as a treatment for COVID-19 infection?

Recently the internet has been abuzz with new ideas to treat COVID-19, including hyperbaric oxygen (HBO2) therapy, undoubtedly driven by the fact that until recently there have been few therapeutic options for this highly contagious and often lethal infection. . . . Refractory hypoxemia is certainly treatable with hyperbaric oxygen due to the obvious effect of increasing inspired oxygen partial pressure (PO2), the major reason for using HBO2 for its established indications. However, the length of time during which patients can safely be administered HBO2 inside a chamber is limited, due to practical issues of confinement and isolation from other necessary medical interventions, but also because of oxygen toxicity.

Gunshot damage to monoplace hyperbaric chamber acrylic.

Introduction: Health care workers are vulnerable to workplace violence, including active shooter incidents. Little is known about how firearms could damage monoplace chamber acrylic and whether a breached pressurized chamber presents additional threat to the patient or bystanders. Methods: In a remote area where firearm discharge is permitted, we tested the durability of sections of monoplace hyperbaric chamber acrylic under various firearm discharges. Firearms were discharged at acrylic sections from a distance of 17 feet at 45 degrees and 10 degrees from perpendicular while wearing protective gear. Firearm calibers ranged from .22 caliber handgun to 5.56 mm AR-15 rifle. We also conducted similar testing on a monoplace hyperbaric chamber pressurized with >99% oxygen to a differential pressure of 14.7 psig (2.0 atmospheres absolute at sea level). Handguns were remotely fired at a distance of 12 feet from the chamber (30 degrees from perpendicular), while the rifles were fired at a distance of 60 feet from the chamber. Result: Higher-caliber handguns penetrated or fractured the acrylic sections only after multiple shots. The tested rifles caused full-thickness penetration and fracture with a single shot. However, the pressurized monoplace hyperbaric chamber required two shots from the AR-15 rifle, separated by approximately 60 mm, to penetrate the acrylic, resulting in rapid depressurization. The chamber otherwise remained intact, with no explosion or conflagration observed. Conclusion: An intact or pressurized chamber performs differently than stand-alone acrylic sections under firearms testing. In a worst-case active shooter scenario, the pressurized monoplace chamber tested posed no additional threat to bystanders beyond the significant risk of ricochet.

Carbon monoxide poisoning.

Despite established exposure limits and safety standards as well as the availability of carbon monoxide (CO) alarms, each year 50,000 people in the United States visit emergency departments for CO poisoning. Carbon monoxide poisoning can occur from brief exposures to high levels of CO or from longer exposures to lower levels. Common symptoms can include headaches, nausea and vomiting, dizziness, general malaise, and altered mental status. Some patients may have chest pain, shortness of breath, and myocardial ischemia, and may require mechanical ventilation and treatment of shock. Individuals poisoned by CO often develop brain injury manifested by neurological problems, including cognitive sequelae, anxiety and depression, persistent headaches, dizziness, sleep problems, motor weakness, vestibular and balance problems, gaze abnormalities, peripheral neuropathies, hearing loss, tinnitus, Parkinsonian-like syndrome, and other problems. In addition, some will have cardiac issues or other ailments. While breathing oxygen hastens the removal of carboxyhemoglobin (COHb), hyperbaric oxygen (HBO2) hastens COHb elimination and favorably modulates inflammatory processes instigated by CO poisoning, an effect not observed with breathing normobaric oxygen. Hyperbaric oxygen improves mitochondrial function, inhibits lipid peroxidation transiently, impairs leukocyte adhesion to injured microvasculature, and reduces brain inflammation caused by the CO-induced adduct formation of myelin basic protein. Based upon three supportive randomized clinical trials in humans and considerable evidence from animal studies, HBO2 should be considered for all cases of acute symptomatic CO poisoning. Hyperbaric oxygen is indicated for CO poisoning complicated by cyanide poisoning, often concomitantly with smoke inhalation.

Eye tracker outcomes in a randomized trial of 40 sessions of hyperbaric oxygen or sham in participants with persistent post concussive symptoms.

PURPOSE: Eye movements may offer a sensitive method to measure response to intervention in mild traumatic brain injury (mTBI). METHODS: The Brain Injury and Mechanisms of Action of Hyperbaric Oxygen for Persistent Post-Concussive Symptoms after Mild Traumatic Brain Injury Study (BIMA) randomized 71 participants to 40 sessions of hyperbaric oxygen or sham. A companion normative study (Normal) enrolled 75 participants. An eye tracking system measured left and right eye movements for saccadic and smooth pursuit. At baseline two smooth pursuit tasks, circular and horizontal ramp, and four saccadic tasks, horizontal and vertical step, reading, and memory guided-on tasks differentiated BIMA from Normal participants. The change from baseline in these tasks were measured and compared between interventions and against Normal participants at 13 weeks and six-month follow-up using the two-sample t-test. The Holm-Bonferroni procedure was used to adjust for multiple testing. RESULTS: Change from baseline in eyetracker measures for participants assigned to the hyperbaric oxygen arm did not significantly differ from those assigned to the sham arm at post-randomization time points 13 weeks and six months. Consistent shifts of BIMA participant values toward Normal values at 13 weeks and six months were observed for overall fixation duration, forward saccadic duration, and number of lines read for the reading task, number of misses on the memory guided-on task, and absolute intersaccadic interval velocity and absolute saccadic amplitude on the circular task. The distributions between Normal and BIMA participants were no longer statistically significantly different at 13 weeks and six months post enrollment for these measures. CONCLUSION: The baseline differences between BIMA and Normal suggest potential vulnerability of the smooth pursuit system and the saccadic system. During the six-month follow-up period, improvement toward Normal was seen on some measures in both the hyperbaric oxygen and sham intervention arms without difference between intervention groups. IDS: clinicaltrials.gov Identifiers NCT01611194 and NCT01925963.

Adverse events and blinding in two randomized trials of hyperbaric oxygen for persistent post-concussive symptoms.

Safety monitoring and successful blinding are important features of randomized, blinded clinical trials. We report chamber- and protocol-related adverse events (AEs) for participants enrolled in two randomized, double-blind clinical trials of hyperbaric oxygen (HBO2) for persistent post-concussive symptoms clinicaltrials.gov identifiers NCT01306968, HOPPS, and NCT01611194, BIMA), as well as the success of maintaining the blind with a low-pressure sham control arm. In both studies, participants were randomized to receive HBO2 (1.5 atmospheres absolute, >99% oxygen) or sham chamber sessions (1.2 atmospheres absolute, room air). In 143 participants undergoing 4,245 chamber sessions, chamber-related adverse events were rare (1.1% in the HOPPS study, 2.2% in the BIMA study). Minor, non-limiting barotrauma was the most frequently reported. Rarely, some participants experienced headache with chamber sessions. No serious adverse events were associated with chamber sessions. An allocation questionnaire completed after intervention revealed that the sham control arm adequately protected the blind in both trials. Participants based allocation assumptions on symptom improvement or lack of symptom improvement and could not discern intervention arm by pressure, smell, taste, or gas flow.

Analysis of magnetic resonance spectroscopy relative metabolite ratios in mild traumatic brain injury and normative controls.

INTRODUCTION: We evaluated magnetic resonance spectroscopy (MRS) in United States military personnel with persistent symptoms after mild traumatic brain injury (mTBI), comparing over time two groups randomized to receive hyperbaric oxygen or sham chamber sessions and a third group of normative controls. METHODS: Active-duty or veteran military personnel and normative controls underwent MRS outcome measures at baseline, 13 weeks (mTBI group only), and six months. Participants received 3.0 Tesla brain MRS for analysis of water-suppressed two-dimensional (2D) multivoxel 1H-MRS of the brain using point resolved spectroscopy (PRESS) with volume selection localized above the lateral ventricles and within the brain parenchyma, of which one voxel was chosen in each hemisphere without artifact. Script-based automatic data processing was used to assess N-acetylaspartate (NAA), creatine (Cr), and choline (Cho). Metabolite ratios for white matter were then calculated for NAA/Cr (Area), Cho/Cr (Area), and Cho/NAA (Area). These ratios were compared using standard analysis methodology. RESULTS: There were no observable differences between participants with mTBI and normative controls nor any observable changes over time in the NAA/Cr (area), Cho/Cr (area), and Cho/NAA (area) ratios. Similarly, the control and injured participants were indistinguishable. DISCUSSION: While participants with mild TBI showed no difference in MRS compared to normative controls, our results are limited by the few voxels chosen and potentially by less sensitive MRS markers.

A composite outcome for mild traumatic brain injury in trials of hyperbaric oxygen.

INTRODUCTION: Global outcomes can strengthen inferences from clinical trials. We evaluate global outcomes for persistent post-concussive symptoms (PCS) after mild traumatic brain injury (mTBI) in two clinical trials of hyperbaric oxygen (HBO2) in United States service members. METHODS: During study design, outcomes of symptom, cognitive, and functional impairments planned for a trial of HBO2 for PCS (HOPPS) were weighted and grouped into different domains to formulate the composite outcome total score. The composite outcome was compared between the intervention groups in HOPPS and those in a subsequent HBO2 trial (BIMA) for validation. Additionally, two post hoc global outcome measures were explored, including one composed of components that demonstrated favorable characteristics in both studies and another via components used in another TBI randomized trial (COBRIT). RESULTS: In total, 143 active-duty or veteran military personnel were randomized across the two studies. Composite total scores improved from baseline for HBO2 (mean ± SD -2.9±9.0) and sham (-2.9±6.6) groups in HOPPS but did not differ significantly between groups (p=0.33). In BIMA, 13-week changes from baseline favored the HBO2 group (-3.6±6.4) versus sham (-0.3±5.2; p=0.02). No between-group differences were found when COBRIT composite scoring was applied to BIMA. Overall, HBO2 effects were maximized when the post hoc global measure derived from both studies was applied to the data. CONCLUSIONS: Composite total scores in HOPPS and BIMA were consistent with primary study results. The global measures considered may offer utility as endpoints to achieve maximal HBO2 effect in future trials of the mTBI population. IDS: clinicaltrials.gov Identifiers NCT01611194 (BIMA) and NCT01306968 (HOPPS).

Extended follow-up in a randomized trial of hyperbaric oxygen for persistent post-concussive symptoms.

To date, several Department of Defense (DoD) and civilian studies have evaluated hyperbaric oxygen for mild forms of traumatic brain injury. Prior to the DoD-sponsored "Brain Injury and Mechanisms of Action of Hyperbaric Oxygen for Persistent Post-Concussive Symptoms after Mild Traumatic Brain Injury (mTBI) (BIMA)" trial, none included post-intervention follow-up beyond three to six months. Post-hoc attempts at long-term follow-up were complicated by low participation and potential self-selection bias. BIMA planned for follow-up through 12 months but was amended to add post-concussive and post-traumatic stress disorder, quality of life, pain, depression, anxiety, and alcohol use assessments at 24 and 36 months. A total of 42 of 71 BIMA participants consented to extendedfollow-up, and 40 and 14 completed a 24- or 36-month visit, respectively, representing an overall response rate of 59% and 20%. Participants who completed extended follow-up were similar to the study group that did not in terms of demographics, perceived intervention allocation, and initial response to intervention. There were no significant differences at 24 or 36 months between intervention groups, and group mean scores were near pre-intervention values. This return to baseline could be due to waning treatment effect, selection bias, or participant or perception effects. Though BIMA implemented several participant retention strategies, more frequent participant contact and increased compensation might improve long-term retention in future studies. clinicaltrials.gov Identifier NCT01611194.

Hyperbaric oxygen for mTBI-associated PCS and PTSD: Pooled analysis of results from Department of Defense and other published studies.

BACKGROUND: Some clinical trials report improvement in persistent post-concussive symptoms (PCS) with hyperbaric oxygen (HBO2) following mild traumatic brain injury (mTBI), but questions remain regarding the utility of HBO2 for PCS, the effects of HBO2 on post-traumatic stress disorder (PTSD), and the influences of sham control exposures. METHODS: A systematic review and pooled analysis was conducted to summarize available evidence for HBO2 in mTBI-associated PCS ± PTSD. Data aggregated from four Department of Defense (DoD) studies with participant-level data (n=254) were grouped into pooled HBO2 and sham intervention groups. Changes from baseline to post-intervention on PCS, PTSD, and neuropsychological measures were assessed using linear mixed models to evaluate main intervention and intervention-by-baseline PTSD effects. Potential dose-response relationships to oxygen partial pressures were investigated. Intervention effects from three other published studies with summary-level participant data (n=135) were also summarized.. RESULTS: Pooled DoD data analyses indicated trends toward improvement favoring HBO2 for PCS (Rivermead Total Score: -2.3, 95% CI [-5.6, 1.0], p=0.18); PTSD (PTSD Checklist Total Score: -2.7, 95% CI [-5.8, 0.4], p=0.09); and significant improvement in verbal memory (CVLT-II Trial 1-5 Free Recall: 3.8; 95% CI [1.0, 6.7], p=0.01). A dose-response trend to increasing oxygen partial pressure was also found, with a greater HBO2 effect in mTBI-associated PTSD suggested. The direction of results was consistent with other published studies. CONCLUSION: A definitive clinical trial, with an appropriate control group, should be considered to identify the optimal HBO2 dosing regimen for individuals with mTBI-associated PTSD ± PCS.

Longitudinal study of hyperbaric oxygen intervention on balance and affective symptoms in military service members with persistent post-concussive symptoms.

BACKGROUND: Dizziness and imbalance are common after mild traumatic brain injury (mTBI). Hyperbaric oxygen (HBO2) has been proposed for persistent post-concussive symptoms after mTBI, but its effect on vestibular function is unknown. OBJECTIVE: To describe balance function in military service-members before and after intervention, and to explore the influence of post-traumatic stress disorder (PTSD), anxiety, and depression on vestibular outcomes. METHODS: Seventy-one participants with mTBI and seventy-five healthy adults without brain injury were enrolled (NCT01611194 and NCT01925963). mTBI participants were randomized to 40 HBO2 sessions or 40 sham chamber sessions over 12 weeks. Normative controls received no intervention. Balance and neuropsychological function were measured at baseline, 13 weeks, and 6 months. RESULTS: The mTBI cohort performed worse than healthy controls on balance and gait measures and reported more affective symptoms. Some within-group improvements were noted at 13 weeks and 6 months. Significant between-intervention differences on balance measures were minimal but effects on postural control generally favored HBO2. Those with affective symptoms, particularly PTSD, had the most improvement in postural control and otolith function following 13 weeks of HBO2. CONCLUSION: HBO2 may influence balance function after mTBI, particularly in those with affective symptoms.

Effects of sprint interval training on cardiorespiratory fitness while in a hyperbaric oxygen environment.

Objectives: Hyperbaric oxygen (HBO2) exposure may enhance cardiorespiratory fitness. Exercise training and HBO2 exposure stimulate mitochondrial biogenesis, increase capillary density, and induce adaptive antioxidant mechanisms. We hypothesized that an exercise regimen of sprint interval training (SIT) while breathing HBO2 would lead to a greater improvement in exercise performance compared to the same training breathing ambient air. Methods: Healthy long-term intermediate-altitude residents, ages 20-39 years, with normal spirometry and cardiorespiratory fitness were randomized to two groups: one performing six sessions of a SIT regimen over two weeks in a hyperbaric chamber (1.4 ATA [141.9 kPa], FiO2=1.0); the other performing under ambient pressure conditions (0.85 ATA [86.1 kPa], FiO2=0.21). Training effect was evaluated by comparing incremental cycle ergometry cardiopulmonary exercise testing before and after the training regimen. The primary outcome measure was peak oxygen consumption (V̇O2), while secondary outcomes included additional exercise parameters. The effect of study group on exercise parameters was assessed using two-factor repeated measures ANOVA. Results: Of 58 participants randomized, 49 completed the training program and all cardiopulmonary exercise tests (n=23 HBO2, n=26 ambient). Both groups experienced an increase in peak V̇O2: 8.1% HBO2 and 7.1% ambient; the differences were not significant (p=0.50). Secondary parameters of peak work rate and peak V̇E experienced a significantly higher change in the HBO2 group compared to the ambient group (p=0.05 and p=0.03, respectively). Conclusion: Cardiorespiratory fitness improved after a two-week SIT regimen, but improvement in peak V̇O2 was not significantly different between ambient and HBO2 groups.

Sleep assessment in a randomized trial of hyperbaric oxygen in U.S. service members with post concussive mild traumatic brain injury compared to normal controls.

STUDY OBJECTIVE: In this exploratory, double-blind, longitudinal sham-controlled trial of hyperbaric oxygen (HBO2) for military personnel with post concussive mild traumatic brain injury (mTBI), self-reports and objective measures of sleep-wake disturbances were assessed and compared to normals. METHODS: Self-reports consisting of Pittsburg Sleep Quality Index (PSQI), sleep diary, screening for obstructive sleep apnea (OSA) risk, restless legs syndrome (RLS), cataplexy, and objective actigraphic measures of sleep-wake were obtained on 71 military personnel with mTBI [baseline, 13 weeks and six months post-randomization (post-intervention)], of which 35 met post-traumatic stress disorder (PTSD) criteria, and 75 healthy volunteers (baseline). Baseline between-group and follow-up changes from baseline overall and within subgroups were evaluated. Mild TBI was defined as consisting of head injury associated loss of consciousness (<24 h), post-traumatic amnesia, and neurological deficits. RESULTS: Sleep quality by self-reports was markedly degraded in the mTBI group at baseline compared to a normative cohort; insomnia 87.3 versus 2.8%, OSA risk 70% versus 1.3%, RLS 32.4% versus and 2.7%. (all p-values <0.001), but actigraphy measures did not differentiate between groups. HBO2 compared to sham treatment improved self-reports of PSQI sleep measures, reports (five out of eight at 13-weeks and two out of eight at six-months). However, other sleep-wake measures were not different. CONCLUSIONS: Perceived sleep quality was markedly disrupted in mTBI military personnel and sleep-wake disturbances were prevalent compared to a normative cohort. HBO2 relative to sham improved some measures of sleep quality on the PSQI, but other measures of sleep were not significantly different.

Hyperbaric oxygen for post-concussive symptoms in United States military service members: a randomized clinical trial.

BACKGROUND: In prior military randomized trials, participants with persistent symptoms after mild traumatic brain injury (TBI) reported improvement regardless of receiving hyperbaric oxygen (HBO2) or sham intervention. This study's objectives were to identify outcomes for future efficacy trials and describe changes by intervention. METHODS: This Phase II, randomized, double-blind, sham-controlled trial enrolled military personnel with mild TBI and persistent post-concussive symptoms. Participants were randomized to receive 40 HBO2 (1.5 atmospheres absolute (ATA), ⟩99% oxygen, 60 minutes) or sham chamber sessions (1.2 ATA, room air, 60 minutes) over 12 weeks. Participants and evaluators were blinded to allocation. Outcomes assessed at baseline, 13 weeks and six months included symptoms, quality of life, neuropsychological, neurological, electroencephalography, sleep, auditory, vestibular, autonomic, visual, neuroimaging, and laboratory testing. Participants completed 12-month questionnaires. Intention-to-treat results are reported. RESULTS: From 9/11/2012 to 5/19/2014, 71 randomized participants received HBO2 (n=36) or sham (n=35). At baseline, 35 participants (49%) met post-traumatic stress disorder (PTSD) criteria. By the Neurobehavioral Symptom Inventory, the HBO2 group had improved 13-week scores (mean change -3.6 points, P=0.03) compared to sham (+3.9 points). In participants with PTSD, change with HBO2 was more pronounced (-8.6 vs. +4.8 points with sham, P=0.02). PTSD symptoms also improved in the HBO2 group, and more so in the subgroup with PTSD. Improvements regressed at six and 12 months. Hyperbaric oxygen improved some cognitive processing speed and sleep measures. Participants with PTSD receiving HBO2 had improved functional balance and reduced vestibular complaints at 13 weeks. CONCLUSIONS: By 13 weeks, HBO2 improved post-concussive and PTSD symptoms, cognitive processing speed, sleep quality, and balance function, most dramatically in those with PTSD. Changes did not persist beyond six months. Several outcomes appeared sensitive to change; additional studies are warranted.

Another perspective on ACEP policy on critical issues in carbon monoxide poisoning: Invited commentary.

The American College of Emergency Physicians (ACEP) recently published its official policy on the evaluation and management of patients with acute carbon monoxide (CO) poisoning [1], an update of the policy previously published in 2008. Three questions regarding CO poisoning were posed to a 30-person ACEP subcommittee, which employed a comprehensive literature review to attempt to draw conclusions. While this is a major step forward, we feel that their conclusions warrant comment.

Carboxyhemoglobin half-life during hyperbaric oxygen in a patient with lung dysfunction: a case report.

INTRODUCTION: The carboxyhemoglobin half-life (COHb t1/2) during hyperbaric oxygen (HBO2) is often quoted as 23 minutes, derived from the average of two adult male volunteers breathing HBO2 at 3 atmospheres absolute (ATA). However, the mean COHb t1/2 of 12 male volunteer smokers was 26.3 minutes at 1.58 ATA and in 12 non-intubated carbon monoxide (CO) poisoned patients treated at 3 ATA, was 43 minutes. CASE REPORT: An 81-year old male, poisoned by an improperly ventilated natural gas heater, was intubated for coma, then treated with HBO2. His PaO2/FiO2 = 283 from aspiration. His initial COHb was 34.4%, and 18 minutes before HBO2, 5.9%. After a compression interval of 17 minutes, the COHb measured after 22 minutes at 3 ATA was 3.3%. RESULTS: By exponential decay, his COHb t1/2 before HBO2 was 95 minutes. We estimate the range for COHb t1/2 during compression as 62-81 minutes and for the 3-ATA interval, 58 to 49 minutes, respectively. The mid-point estimate of COHb t1/2 at 3 ATA was 53 minutes. CONCLUSIONS: The COHb t1/2 we calculated is greater than previously reported, but longer in our patient possibly because of concomitant respiratory failure, lung dysfunction, and mechanical ventilation. The often-cited COHb t1/2 of 23 minutes, likely underestimates the actual COHb t1/2 in CO-poisoned patients, especially those with cardiopulmonary dysfunction.

Rates of visual acuity change in patients receiving hyperbaric oxygen in monoplace and multiplace chambers.

INTRODUCTION: Changes in visual acuity are a known side effect of hyperbaric oxygen (HBO2). We conducted a quality improvement initiative to better quantify visual change risk and to identify possible risk factors. METHODS: Vision was checked weekly in a clinical HBO2 population by Snellen eye chart. Visual acuity change was defined as Snellen test worsened to 20/40 or greater or by loss of 2 lines. RESULTS: Of 85 patients treated from January 2013 to February 2015 with 10 HBO2 sessions and ≥ 2 weeks of visual acuity testing, 53 (62%) were male. All were treated for UHMS-approved indications. A total of 34 patients (40%) had no change in visual acuity, 27 (32%) had a 1-line change, and 24 (28%) had at least a 2-line worsening in visual acuity. The number of sessions for those with at least a 2-line change was 36 ± 15 (15-60). A 2-line change occurred at similar rates for monoplace and multiplace patients (29% and 32%, respectively), but monoplace patients more frequently reached 20/40 or worse (32% vs. 18%). Seven of 11 patients with existing cataracts had ≥ 2 line change, as did six of 14 patients (43%) with a history of head/neck radiation. CONCLUSIONS: In this retrospective review of quality improvement data, 28% of patients had a 2-line change in visual acuity by Snellen exam after treat-ment with HBO2. Further study of possible risk factors, including chamber type, is warranted.

Ischemic colitis associated with acute carbon monoxide poisoning--a case report.

Carbon monoxide (CO) poisoning is common, but it has rarely been reported to cause ischemic colitis. In this case, a 34-year-old female with depression presented to an emergency department after a period of unconsciousness, with urinary and bowel incontinence, following exposure to car exhaust. Her carboxyhemoglobin level was 23%. She had metabolic acidosis. She was transferred to our facility for hyperbaric oxygen treatment, where she had intractable nausea/vomiting with abdominal pain and bright-red bleeding per rectum. She exhibited lower abdominal tenderness and hypoactive bowel sounds. Vital signs were: temperature 36.8 degrees C; blood pressure 137/ 86 mmHg; heart rate 114 beats/minute; respiratory rate 28 breaths/minute. The patient's electrocardiogram showed sinus tachycardia with T-wave inversions in leads I, aVL and V3-V6. The troponin I level peaked at 3.7 ng/ml. Echocardiogram showed a reduced ejection fraction of 30%-35%, with akinesis in the posterior lateral and distal anterior distributions. Computed tomography of the abdomen revealed diffuse colonic mural thickening, supporting mesenteric ischemia. Sigmoidoscopy showed edematous friable pale mucosa from rectum to distal sigmoid colon. Hyperbaric oxygen was deferred based on the patient's status. Over three days, the initial hematochezia progressed to melena and then resolved. Adenosine cardiac stress MRI was normal. She was transferred to the psychiatry service and discharged four days later. Four years later, she has no gastrointestinal, cardiac or cognitive problems.