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Clinicians often rely on measurement of carboxyhemoglobin (COHb) to confirm or rule out a diagnosis of carbon monoxide (CO) poisoning.We report two cases of false negative COHb in patients with CO poisoning and one case of false positive COHb in a patient without CO poisoning.In the first case, a 20-year-old male developed headache, confusion, and near-syncope while operating a gasoline-powered pressure washer in an enclosed space. In the emergency department (ED), his COHb was 1.8%, but this level was disregarded, and he was referred for hyperbaric oxygen. His COHb just before hyperbaric oxygen was 4.1%, and later analysis of his blood collected at ED arrival revealed a COHb of 20.1%. The referral ED blood gas machine calibration and controls were within specification. In the second case, a 45-year-old male presented with several others to the ED with symptoms of CO poisoning after exposure at a conference. All others had elevated COHb levels, but his COHb was 2%. He was discharged but returned shortly with continued symptoms and requested his COHb be repeated. The repeat COHb was 17% (84 minutes after the first). After three hours of oxygen, his COHb was 7%. In the final case, an 83-year-old non-smoking male presented to an ED with breathlessness and tachypnea and was diagnosed with COVID-19 pneumonia. His COHb was 7.1%, but he reported living in an all-electric home. Another adult who lived with him and rode with him to the ED was asymptomatic and had a COHb of 3%. Later, COHb of 1.9% was measured from blood collected at ED arrival, and gas chromatography/mass spectrometry confirmed this result (2%).COHb levels are not always accurate. Clinicians should use clinical judgment to manage their patients, including rejecting laboratory values that do not fit the clinical situation.

Objective: To describe the structural sequelae of carbon monoxide (CO) poisoning on the heart assessed using stress cardiac MRI (CMR). CO poisoning is common. While acute cardiac injury is frequent among survivors, the mid- and long-term effects of CO on the myocardium are unclear. Methods: CMR studies performed between the years 2005 and 2014 for a primary diagnosis of CO poisoning at a tertiary care center were reviewed by an experienced cardiologist. Variables of interest were compared between patients with normal and abnormal studies to identify factors associated with cardiac dysfunction. Results: Eighty-eight patients underwent stress CMR, age 34 years (range 11-70); 49% were male, 74 had acute poisoning and 14 had chronic poisoning (CO exposure for longer than 24 hours). Time from CO poisoning to imaging was 24 months (1day-120 months). Patients were stratified into four categories, which included those with acute poisoning imaged: • ≤12 months; • 12-60 months; • >60 months from the event; and • those with chronic poisoning. Overall, 26 studies (30%) were abnormal. The most common findings were: left ventricular systolic dysfunction in 14 patients, right ventricular systolic dysfunction in nine, and LV dilatation in six. Abnormalities were mild in most cases and were equally prevalent in all four patient categories. Dyspnea at the time of follow-up was more frequent among those with abnormal studies. Conclusions: Mild alterations in ventricular structure and function are frequent in survivors of CO poisoning. Myocardial scarring is rare, suggesting that acute hypoxic injury may not fully explain these abnormalities.

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. Conclusions: 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.

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.

Background Audiology clinics have many tools available to evaluate auditory and vestibular complaints. However, many tools lack established normative ranges across the life span. We conducted this study to establish reference ranges across the life span for audiology/vestibular measures commonly used to evaluate patients with traumatic brain injury. Materials and Methods In this repeated measures study, 75 adults, ages 18-65 years, without a history of traumatic brain injury, underwent robust auditory/vestibular evaluations three times over six months, including rotational chair, videonystagmography, computerized dynamic posturography, vestibular evoked myogenic potentials, and retinal fundoscopy. Results Age effect was notable for transient evoked otoacoustic emissions, pure-tone audiometry, auditory brainstem response, auditory middle latency response, and auditory-steady state response at 4000 hertz (Hz). Older participants (50-65 years) were more likely to have delayed latency horizontal saccades, positional nystagmus, slowed lower-extremity motor control responses, and delayed latency ocular vestibular evoked myogenic potentials. Low to mid-frequency horizontal (0.003-4 Hz) and mid-frequency vertical (1-3 Hz) vestibulo-ocular reflex, otolith-mediated reflexes, dynamic visual acuity and balance measures were generally not influenced by age. Females had larger static subjective visual testing offset angles, longer cervical vestibular evoked myogenic potential P1 latency, faster velocity horizontal saccades, and quicker motor control latency for large backward translations than age-matched males. Conclusion These reference ranges can be used to discern impairment within the auditory and vestibular pathway following traumatic brain injury in young to middle-aged adults. ID TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT01925963.

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).

Traumatic brain injury (TBI) is a major cause of death and disability in the United States (U.S.), with the Centers for Disease Control and Prevention reporting approximately 2.8 million TBI-related emergency department visits, hospitalizations, and deaths in 2012 [1]. For those under 45 years of age, TBI is the number one cause of disability and mortality worldwide [2]. Within military populations TBI remains especially problematic. While the incidence of TBI in the U.S. military peaked in 2011, Department of Defense personnel continue to experience approximately 18,000 new cases each year, with 383,473 total cases between 2000 and the first quarter of 2018 [3]. Eighty-two percent of these injuries were classified as mild TBI (mTBI) [3].

Introduction: Individuals with persistent symptoms after mild traumatic brain injury (mTBI) often have auditory complaints. In this study, we used the auditory brainstem response (ABR) to determine whether cochlear synaptopathy could explain auditory symptoms. Methods: 69 adult military service members with mTBI and 25 adults without brain injury (NCT01611194 and NCT01925963) completed pure-tone audiometry, ABR, and central auditory processing tests. All participants were male, ages 21-50. Results: 37/69 mTBI participants had measurable hearing loss, while another 20-30% had hearing complaints or tinnitus. While mTBI participants with measurable hearing loss had reduced wave I and III amplitude and decreased III-V interpeak latency, those with no measurable hearing loss did not significantly differ from controls on any ABR parameter. Those with measurable hearing loss were also more likely to have abnormal central auditory processing. mTBI participants with no measurable hearing loss but who reported hearing concerns had some ABR findings (III-V interpeak latency, I and V amplitudes, V/I amplitude ratio) more like the measurable hearing loss mTBI group than normative controls. Conclusion: Cochlear synaptopathy may have contributed to some of the auditory impairment in service members with mTBI with measurable hearing loss. However, these results are likely confounded by cochlear hair cell damage.

Functional magnetic resonance imaging (fMRI) has been available commercially for clinical diagnostic use for many years. However, both clinical interpretation of fMRI by a neuroradiologist and quantitative analysis of fMRI data can require significant personnel resources that exceed reimbursement. In this report, a fully automated computerbased quantification methodology (Enumerated Auditory Response, EAR) has been developed to provide an auditory fMRI assessment of patients who have suffered a mild traumatic brain injury. Fifty-five study participants with interpretable auditory fMRI sequence data were assessed by EAR analysis, as well as both clinical radiologist fMRI interpretation and voxelwise general linear model (GLM) analysis. Comparison between the clinical interpretation and the two computer analysis methods resulted in 67% concordance (identical), 32% near-concordance (one level difference), and 1% discordant. Comparison between the clinical computer-based quantification (EAR) and GLM analysis yielded significant correlations in right and left ear responses (p

To describe the structural sequelae of carbon monoxide (CO) poisoning on the heart assessed using stress cardiac MRI (CMR). CO poisoning is common. While acute cardiac injury is frequent among survivors, the mid- and long-term effects of CO on the myocardium are unclear.CMR studies performed between the years 2005 and 2014 for a primary diagnosis of CO poisoning at a tertiary care center were reviewed by an experienced cardiologist. Variables of interest were compared between patients with normal and abnormal studies to identify factors associated with cardiac dysfunction.Eighty-eight patients underwent stress CMR, age 34 years (range 11-70); 49% were male, 74 had acute poisoning and 14 had chronic poisoning (CO exposure for longer than 24 hours). Time from CO poisoning to imaging was 24 months (1 day-120 months). Patients were stratified into four categories, which included those with acute poisoning imaged: ≤12 months; 12-60 months;60 months from the event; and those with chronic poisoning. Overall, 26 studies (30%) were abnormal. The most common findings were: left ventricular systolic dysfunction in 14 patients, right ventricular systolic dysfunction in nine, and LV dilatation in six. Abnormalities were mild in most cases and were equally prevalent in all four patient categories. Dyspnea at the time of follow-up was more frequent among those with abnormal studies.Mild alterations in ventricular structure and function are frequent in survivors of CO poisoning. Myocardial scarring is rare, suggesting that acute hypoxic injury may not fully explain these abnormalities.

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.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 with99% 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.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.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.

Introduction: Carbon monoxide (CO) poisoning causes hypoxia and inflammation, which could adversely affect muscle. We could find no published information about CO poisoning causing myositis. Case report: A 53-year-old previously healthy female semi-truck driver had CO poisoning from a faulty diesel engine exhaust intermittently over three months, culminating in an episode of acute CO poisoning, with syncope after exiting the truck at the end of the three-month period. Neuropsychological symptoms immediately after the acute poisoning event were followed by the development of fatigue, weakness and myalgias within two months and a diagnosis of “polymyositis” within four months. C-reactive protein and creatine kinase were elevated. Electromyogram showed pure myopathy without sensory abnormalities. Occult malignancy was ruled out. Thigh muscle biopsy revealed severe inflammatory myopathy and myonecrosis. Muscle specialist pathologists interpreted the biopsy as toxic or viral inflammatory myopathy, not polymyositis, with CO poisoning as the likely etiology. She received steroids and mycophenolate. Nineteen months later, a repeat biopsy was negative for inflammation or myopathic process. Alternative diagnoses were ruled out by clinical investigation and her course over the next five years. Conclusions: This patient’s presentation and clinical course support a diagnosis of myositis from CO poisoning, although it is possible that the myositis was either idiopathic or post-viral (without evidence of a causative virus).

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 ran- domized 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 evalua- tors 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 parti- cipants 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.

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.

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.

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.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..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.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.

Individuals with persistent symptoms after mild traumatic brain injury (mTBI) often have auditory complaints. In this study, we used the auditory brainstem response (ABR) to determine whether cochlear synaptopathy could explain auditory symptoms.69 adult military service members with mTBI and 25 adults without brain injury (NCT01611194 and NCT01925963) completed pure-tone audiometry, ABR, and central auditory processing tests. All participants were male, ages 21-50.37/69 mTBI participants had measurable hearing loss, while another 20%-30% had hearing complaints or tinnitus. While mTBI participants with measurable hearing loss had reduced wave I and III amplitude and decreased III-V interpeak latency, those with no measurable hearing loss did not significantly differ from controls on any ABR parameter. Those with measurable hearing loss were also more likely to have abnormal central auditory processing. mTBI participants with no measurable hearing loss but who reported hearing concerns had some ABR findings (III-V interpeak latency, I and V amplitudes, V/I amplitude ratio) more like the measurable hearing loss mTBI group than normative controls.Cochlear synaptopathy may have contributed to some of the auditory impairment in service members with mTBI with measurable hearing loss. However, these results are likely confounded by cochlear hair cell damage.

Purpose: Military service members often report both affective and vestibular complaints after mild traumatic brain injury (mTBI), but associations between symptoms and vestibular deficits can be subtle and inconsistent. Methods: From two complementary studies, one of military service members with persistent post-concussive symptoms after mTBI (NCT01611194) and the other of adult volunteers with no history of brain injury (NCT01925963), affective symptoms were compared to postural control, gait, otolith and visuospatial function. Results: The studies enrolled 71 participants with mTBI and 75 normative controls. Participants with mTBI had significantly reduced postural equilibrium on the sensory organization test (SOT), and more so in those with high anxiety or post-traumatic stress. Cervical and ocular vestibular evoked myogenic potentials (cVEMP; oVEMP) showed prolonged latencies in mTBI participants compared to controls; oVEMPs were significantly delayed in mTBI participants with high anxiety, post-traumatic stress or depression. A subset of the mTBI group had abnormal tandem gait and high anxiety. Anxiety, posttraumatic stress, and depression did not correlate with performance on the 6-Minute Walk Test, visuospatial neuropsychological measures, and the Satisfaction with Life Scale in the mTBI group. Conclusions: In this study military service members with mTBI reported affective symptoms, concurrently with vestibular-balance concerns. Worse scores on affective measures were associated with abnormal findings on measures of postural control, gait and otolith function.

Functional magnetic resonance imaging (fMRI) has been available commercially for clinical diagnostic use for many years. However, both clinical interpretation of fMRI by a neuroradiologist and quantitative analysis of fMRI data can require significant personnel resources that exceed reimbursement. In this report, a fully automated computer-based quantification methodology (Enumerated Auditory Response, EAR) has been developed to provide an auditory fMRI assessment of patients who have suffered a mild traumatic brain injury. Fifty-five study participants with interpretable auditory fMRI sequence data were assessed by EAR analysis, as well as both clinical radiologist fMRI interpretation and voxelwise general linear model (GLM) analysis. Comparison between the clinical interpretation and the two computer analysis methods resulted in 67% concordance (identical), 32% nearconcordance (one level difference), and 1% discordant. Comparison between the clinical computer-based quantification (EAR) and GLM analysis yielded significant correlations in right and left ear responses (p⟨0.05) for the full subject group. Automated fMRI quantification analysis equivalent to EAR might be appropriate for both future research projects with constrained resources, as well as possible routine clinical use.

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.

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.

Carbon monoxide (CO) poisoning causes hypoxia and inflammation, which could adversely affect muscle. We could find no published information about CO poisoning causing myositis.A 53-year-old previously healthy female semi truck driver had CO poisoning from a faulty diesel engine exhaust intermittently over three months, culminating in an episode of acute CO poisoning, with syncope after exiting the truck at the end of the three-month period. Neuropsychological symptoms immediately after the acute poisoning event were followed by the development of fatigue, weakness and myalgias within two months and a diagnosis of "polymyositis" within four months. C-reactive protein and creatine kinase were elevated. Electromyogram showed pure myopathy without sensory abnormalities. Occult malignancy was ruled out. Thigh muscle biopsy revealed severe inflammatory myopathy and myonecrosis. Muscle specialist pathologists interpreted the biopsy as toxic or viral inflammatory myopathy, not polymyositis, with CO poisoning as the likely etiology. She received steroids and mycophenolate. Nineteen months later, a repeat biopsy was negative for inflammation or myopathic process. Alternative diagnoses were ruled out by clinical investigation and her course over the next five years.This patient's presentation and clinical course support a diagnosis of myositis from CO poisoning, although it is possible that the myositis was either idiopathic or post-viral (without evidence of a causative virus).

Carbon monoxide poisoning remains common in the United States. One component of effective prevention involves identification of scenarios in which poisoning occurs to guide development of appropriate interventions. This study was conducted to determine the significance of the problem of carbon monoxide poisoning occurring in US hotels, motels and resorts. This is a population-based case series of guests staying at US hotels, motels, and resorts from 2005 to 2018. Details of incidents and individuals poisoned with carbon monoxide were collected from online searches and professional experience of the authors. Data extracted included number of incidents and individuals poisoned, age of those poisoned, outcomes, source of carbon monoxide, and lodging type. From January 1, 2005 to December 31, 2018, 905 guests were poisoned in 115 identified incidents, including 22 fatalities. Children represented 16% of those poisoned and 27% of fatalities. Type of lodgings were hotels, motels, and resorts of all classes and located in a majority of states. Most poisonings were caused by natural gas fueled appliances and could likely have been prevented by an in-room carbon monoxide alarm. To reduce morbidity and mortality from unintentional CO poisoning in lodging facilities, government should mandate installation of in-room CO alarms, similar to the current requirement for smoke alarms.

Early and frequent patient mobilization substantially mitigates risk for post-intensive care syndrome and long-term functional impairment. We developed and tested computer vision algorithms to detect patient mobilization activities occurring in an adult ICU. Mobility activities were defined as moving the patient into and out of bed, and moving the patient into and out of a chair. A data set of privacy-safe-depth-video images was collected in the Intermountain LDS Hospital ICU, comprising 563 instances of mobility activities and 98,801 total frames of video data from seven wall-mounted depth sensors. In all, 67% of the mobility activity instances were used to train algorithms to detect mobility activity occurrence and duration, and the number of healthcare personnel involved in each activity. The remaining 33% of the mobility instances were used for algorithm evaluation. The algorithm for detecting mobility activities attained a mean specificity of 89.2% and sensitivity of 87.2% over the four activities; the algorithm for quantifying the number of personnel involved attained a mean accuracy of 68.8%.

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.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.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.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.

The true incidence of carbon monoxide (CO) poisoning is not clearly known, but a description of possible trends could aid in prevention.Investigators searched Utah state databases for emergency department (ED) visits and admissions for CO poisoning and medical examiner records for CO-related fatalities.From 1996-2013, 7,590 individuals were diagnosed with CO poisoning: 6,469 were treated/ released from EDs; 596 were admitted; 525 died. Of 7,065 non-fatal poisonings, 5,950 (84%) were accidental and 498 (7%) were suicide attempts. Few patients (9.7%) were treated with hyperbaric oxygen. For accidental poisonings, internal combustion engines accounted for 43%, smoke inhalation, 34%, and heating sources, 22%. Internal combustion engines were implicated in 97% of suicide attempts. Non-fatal poisonings declined following a 2008 legislative change requiring CO alarms in residences, but we do not know if legislation caused the decline. One hundred forty-one (27%) fatal poisonings were accidental, 361 (70%) suicides and two (0.4%) homicides. Victims with cardiovascular autopsy findings/past cardiovascular history had lower carboxyhemoglobin levels (mean 51.2%, n=53) compared to those without (70.8%, n=472). Mean postmortem carboxyhemoglobin was highest in ages 20-29 years (72.5%).The incidence of CO poisoning in Utah is declining, but CO poisoning is still common. Alarm legislation may aid prevention efforts. An educational campaign addressing the many causes and circumstances of CO poisoning is required for prevention.

Heart rate variability (HRV) represents measurable output of coordinated structural and functional systems within the body and brain. Both mild traumatic brain injury (mTBI) and HRV are modulated by changes in autonomic nervous system function. We present baseline HRV results from an ongoing mTBI clinical trial. HRV was assessed via 24-hour ambulatory electrocardiography; recordings were segmented by physiological state (sleep, wakefulness, exercise, standing still). Time, frequency, and spatial domain measures were summarized and compared with symptoms, sleep quality, and neurological examination. Median low frequency/high frequency (LF/HF) ratio exceeded 1.0 across segments, indicating prevalence of sympathetic modulation. Abnormal Sharpened Romberg Test was associated with 29% LF/HF decrease (95% CI [2.1, 47.7], p=0.04); pathological nystagmus associated with decreased standard deviation of electrocardiogram R-R interval (SDNN) index (25% decrease, 95% CI [0.8, 43.4], p=0.04). Increased sympathetic modulation was associated with increased anger scores (19% LF/HF increase with 5-point State Trait Anger Expression Inventory-2 trait anger increase (95% CI [1.2, 39.1], p=0.04)). A 13% HF increase (95% CI [2.1, 25.7], p=0.02) was observed with increased Pittsburgh Sleep Quality Index scores. These results support autonomic nervous system dysfunction in service members after mTBI.ClinicalTrials.gov Identifier: NCT01611194; https://clinicaltrials.gov/show/NCT01611194.

The Brain Injury and Mechanism of Action of Hyperbaric Oxygen for Persistent Post-Concussive Symptoms after Mild Traumatic Brain Injury (mTBI) (BIMA) study, sponsored by the Department of Defense and held under an investigational new drug application by the Office of the Army Surgeon General, is one of the largest and most complex clinical trials of hyperbaric oxygen (HBO₂) for post-concussive symptoms (PCS) in U.S. military service members.

We report results of an observational cohort study investigating long-term follow-up in participants from two completed United States military trials of hyperbaric oxygen (HBO₂) for persistent post-concussive symptoms (PCS), as well as challenges in recruitment and retention in active-duty military personnel. After informed consent, participants completed an electronic survey assessing PCS, post-traumatic stress disorder (PTSD), anxiety, depression and quality of life. Of 132 HBO₂ study participants, 40 (30%) completed the survey (42 could not be contacted; 50 were lost to follow-up or declined). All were male, age 28.1 ±6.6 years (mean ±1SD). Time to follow-up was 39.2 ±6.1 months. At follow-up, participants reported continued symptoms of PTSD, depression, anxiety and reduced quality of life. Among DARPA/VCU study participants, total PCS scores worsened in the 1.5 atmospheres absolute (ATA) equivalent HBO₂ group (mean change 7.4 ±15.8) and improved in the sham (-8.0 ±7.7) and 2.0 atmospheres absolute equivalent HBO₂ groups (-3.3 ±7.4). Individual changes varied widely, range -23 to +28 points. In participants from the HOPPS study, total PCS scores worsened in all groups: local care (10.5 ±8.7), sham (7.9 ±11.9) and 1.5 ATA HBO₂ (1.0 ±19.4). In this limited, cross-sectional sample, PCS and PTSD symptoms did not appear to improve over time by descriptive analyses. Low participation rates and potential response bias limit our ability to perform statistical hypothesis testing and to draw conclusions from these data. Future studies should prospectively plan longitudinal follow-up and regular engagement with participants to minimize attrition.

Background Symptoms of carbon monoxide (CO) poisoning are non-specific. Diagnosis requires suspicion of exposure, confirmed by measuring ambient CO levels or carboxyhemoglobin (COHb). An FDA-approved pulse oximeter (Rad-57) can measure CO saturation (S(pCO)). The device accuracy has implications for clinical decision-making. Methods From April 1 to August 15, 2008, study personnel measured S(pCO) and documented demographic factors at time of clinical blood draw, in a convenience sample of 1,363 subjects presenting to the emergency department at Intermountain Medical Center, Murray, Utah. The technician then assayed COHb. COHb and S(pCO) values were compared by subject; false positive or negative values were defined as S(pCO) at least 3 percentage points greater or less than COHb level, reported by the manufacturer to be ± 1 SD in performance. Results In 1,363 subjects, 613 (45%) were male, 1,141 (84%) were light-skinned, 14 in shock, 4 with CO poisoning, and 122 (9%) met the criteria for a false positive value (range 3-19 percentage points), while 247 (18%) met the criteria for a false negative value (-13 to -3 percentage points). Risks for a false positive S(pCO) reading included being female and having a lower perfusion index. Methemoglobin, body temperature, and blood pressure also appear to influence the S(pCO) accuracy. There was variability among monitors, possibly related to technician technique, as rotation of monitors among technicians was not enforced. Conclusions While the Rad-57 pulse oximeter functioned within the manufacturer's specifications, clinicians using the Rad-57 should expect some S(pCO) readings to be significantly higher or lower than COHb measurements, and should not use S(pCO) to direct triage or patient management. An elevated S(pCO) could broaden the diagnosis of CO poisoning in patients with non-specific symptoms. However, a negative S(pCO) level in patients suspected of having CO poisoning should never rule out CO poisoning, and should always be confirmed by COHb.

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.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.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.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.

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.

Simple reaction time (SRT) and procedural reaction time (PRT) are speed-of-processing tasks in the Automated Neuropsychological Assessment Metrics (ANAM) that may be sensitive to mild traumatic brain injury (mTBI). The investigators measured SRT and PRT throughput (correct responses per minute) at baseline, 6 weeks, and 13 weeks in military personnel with mTBI randomized to local care or 40 chamber sessions (sham-1.2 atmospheres absolute [ATA] air, hyperbaric oxygen-1.5 ATA O2). Scores were assessed at baseline using univariate analysis of variance and across time with repeated measures methods. Data reported as throughput standard scores (mean = 100, SD = 15). Seventy-two participants with ongoing symptoms after mTBI enrolled in the study (three female, median age 31 years, mean three lifetime concussion events, most recent mTBI 23 months prior). Sixty-four had Automated Neuropsychological Assessment Metrics data at 13 weeks. SRT and PRT throughput standard scores were comparable across groups at baseline. Over time, SRT scores did not change in the hyperbaric oxygen or sham groups and decreased in the local care group. PRT throughput standard scores increased from baseline to mid-intervention and decreased from mid-intervention to postintervention in all groups. Repeated measures change over time in SRT (p = 0.23), and PRT (p = 0.17) scores were not different among groups. This study may be underpowered to detect statistically significant change.

We evaluated the Zyno Medical Z-800F, CME Body Guard 323 Color Vision, and Baxter Flo-Gard 6201 infusion pumps for monoplace chamber conditions. We adjusted pump occlusion pressure allowing infusion to 3 atmospheres absolute (atm abs). Baxter and Zyno pumps were connected to the chamber pass-through with rigid small-bore tubing. The CME infusion set was connected directly to the pass-through. We infused saline to a collection manifold inside a monoplace chamber at 1-100 mL/ hour under pressures ranging from 0.85-3.0 atm abs. We averaged results from three to five separate tests for each condition. At baseline, pumps performed within ±10% of expected (our measurement capability). However, clinical engineering verified performance within manufacturer specifications (±5% at atmospheric pressure). During a carbon monoxide hyperbaric protocol (3 atm abs/2 atm abs), measured flow with the Baxter, CME and Zyno pumps was ±5% of setting at 10 mL/hour (95%, 103%, 95%, respectively); at 1 mL/hour, average flow were 91%, 83%, 83%, respectively. During timed testing (volume recorded before decompression), pump accuracy was ±10% at 10 and 100 mL/hour. Tubing compliance compromised performance at lower flow rates, magnified by increased pressure. These pumps have potential for monoplace chamber use, although not supported by the manufacturers or FDA-cleared. At low flow rates, tubing compliance affects delivered volumes.

Newer pulse CO-oximeters provide a non-invasive and quick means of measuring oxyhemoglobin, carboxyhemoglobin and methemoglobin. Clubbing has been reported to cause inaccuracy in pulse oximeters. We present a case of inaccurate carboxy-hemoglobin measurement by pulse CO-oximetry due to digital clubbing. An 18-year-old man with a history of cystic fibrosis presented after a suicide attempt by inhalation of exhaust. At the initial emergency department evaluation, his blood carboxyhemoglobin was 33%. He was intubated, placed on 100% oxygen and transferred to our facility. Upon arrival, we placed three different pulse CO-oximeters on different fingers and toes. Carboxyhemoglobin levels measured by these meters ranged from 9%-11%. A venous blood gas drawn on arrival showed a carboxyhemoglobin level of 2.3% after four hours on 100% oxygen by endotracheal tube. Thirty minutes later, we checked arterial blood gas, which revealed a COHb level of 0.9%. Again, non-invasive carboxyhemoglobin measurements read 10%. The patient was treated with hyperbaric oxygen for carbon monoxide poisoning. This case suggests that non-invasive measurements of carboxyhemoglobin should be correlated with the clinic history and with an arterial or venous blood gas oximetry analysis.

Divers and hyperbaric chamber attendants breathe hyperbaric air routinely. Hyperbaric oxygen (HBO2) is used therapeutically frequently. Although much is understood about the hemodynamic physiology and gas exchange effects during hyperbaric air and HBO2 exposure, arterial and pulmonary arterial (PA) catheter data, including blood gas values during hyperbaric air and HBO2 exposure of normal humans, have not been reported. We exposed 10 healthy volunteers instrumented with arterial and PA catheters to air at 0.85, 3.0, 2.5, 2.0, 1.3 (decompression stop), 1.12 (decompression stop), and 0.85 atm abs (our altitude) and then at identical pressures breathing O2 followed by atmospheric pressure air while we measured arterial and PA pressures (PAP), cardiac output (Q̇), and blood gas measurements from both arterial and PA catheters. Although hemodynamic changes occurred during exposure to both hyperbaric air and HBO2, we observed a greater magnitude of change under HBO2 conditions: heart rate changes ranged from −9 to −19% (air to O2), respiratory rate from −12 to −17%, Q̇ from −7 to −18%, PAP from −18 to −19%, pulmonary vascular resistance from −38 to −48%, and right-to-left shunt fraction from −87 to −107%. Mixed venous CO2 fell 8% from baseline during HBO2 despite mixed venous O2 tensions of several hundred Torr. The stroke volume, O2 delivery, and O2 consumption did not change across exposures. The arterial and mixed venous partial pressures of O2 and contents were elevated, as predicted. O2 extraction increased 37% during HBO2.

Pulmonary barotrauma can cause cerebral arterial gas embolism (CAGE) from pulmonary overdistension of alveoli forcing gas into the pulmonary vasculature. We report a case of CAGE in a man found to have occult pulmonary arteriovenous malformation (PAVM) and undiagnosed obstructive sleep apnea (OSA). A 46-year-old man was admitted to the hospital for an acute seizure and left-sided weakness, with telangiectasias on his lower lip and tongue. Brain-computed tomography (CT) showed gas emboli in the right hemisphere. Chest CT revealed a 1.8-cm PAVM in the posterior right costophrenic sulcus. A transthoracic echocardiogram showed no intracardiac shunt or patent foramen ovale. He was treated with phenytoin, lidocaine and hyperbaric oxygen. The PAVM was occluded with a detachable balloon followed by coil embolization. Polysomnography revealed severe obstructive sleep apnea, which was treated with CPAP. Seven years later, the patient was functioning at his pre-event baseline. We propose the CAGE was caused by high negative intrathoracic pressures while breathing against an obstructed upper airway, with air entrainment into the PAVM and subsequent arterialization.

Carbon monoxide (CO) poisoning may result in neurological and neuropsychological sequelae, including visual problems. We performed neuro-optometric evaluation on patients who reported vision or attention complaints after CO poisoning.We performed a retrospective chart review of patients with continued symptoms after CO poisoning who had neuro-optometry evaluations between 8/18/2009 and 8/31/2013. Data collected include general demographics, symptomatic changes prompting neuro-optometric evaluation and pathologic findings during examination.We identified 43 CO-poisoned patients receiving neuro-optometry evaluation (17 male (40%), 26 female (60%)). The patients' mean age was 41 ± 14 years (range 17-72 years), and 28 (65%) had CO exposure durations24 hours. Neuro-optometry evaluations were conducted at 2.4 ± 1.7 years from poisoning (0.05-7.1). Of 37 patients reporting onset of visual symptoms, 34 reported symptom onset within six months of poisoning. Thirty-nine patients (91%) demonstrated visual pathology attributable to CO poisoning. Peripheral vision defects were detected in nine individuals (21%), while central vision defects were noted in only two (5%). Other present findings were: convergence insufficiency 28 patients (65%); oculomotor defects 14 (33%); accommodative dysfunction 10 (23%); divergence insufficiency six (14%), and convergence excess two (5%). Clinical dry eye was present in four (9%). Eleven patients (26%) received visual evoked potential (VEP) testing; eight (73%) were abnormal.These findings support that CO poisoning can result in visual pathology. Of clinical importance, some of these abnormalities may be responsive to rehabilitative interventions. Specialized visual evaluation and testing should be an integral aspect of care in CO-poisoned patients with visual complaints or exam findings.

We evaluated the Hospira Plum A+ (HB) hyperbaric infusion pump under monoplace and multiplace hyperbaric conditions to test pump flow accuracy.Pump flow accuracy was tested in monoplace and multiplace hyperbaric chambers at different rates, fluid viscosities, pressures and volumes. Output was recorded from the pump (programmed) and from graduated cylinders or syringes (actual). The lead acid battery life was recorded for multiplace trials.In monoplace trials to 3.0 atmospheres absolute (atm abs), the pump functioned within the published tolerance of 12.5% at 1 ml/hour (mean deviation +3.3%, range 0.0% to +5.0%) and at faster flow rates (mean deviation -0.4%, range -11.5% to +6.0%). A trial of packed red blood cells (deviation -3.3%) was also within acceptable limits. For all multiplace trials, the pump functioned well within the manufacturer's limits (mean deviation -0.1%, range -0.8% to +0.9%). At the maximum flow rate, the interval to the first battery alarm for two trials was shorter than the duration of a clinical hyperbaric session (first alarm at 82 and 94 minutes). When we examined delivery variances in the compression and decompression phases for monoplace chambers, at 1 ml/hour 25/39 trials (64%) had no measurable infusion volume during compression. Conversely, more than twice the programmed volume was infused during the 10-minute decompression interval (mean 0.40 ml, range 0.32 to 0.60 ml). The tubing compliance effect was also noted, to a lesser degree, in trials at 3 and 5 ml/hour.This infusion pump can be useful in hyperbaric medicine departments that treat patients who need intravenous infusions. Tubing compliance may affect fluid volumes delivered by the pump, especially when delivery rates are low. Careful monitoring of patients with low volume infusions during monoplace chamber compression and decompression is advised.

Some practitioners advocate hyperbaric oxygen (HBO2) for sequelae following brain injury. This study assessed recruitment, tolerance and safety in preparation for a randomized clinical trial.Prospective, open-label feasibility study.Hyperbaric medicine department of a tertiary academic hospital.Participatory adult outpatients with problems from stroke (n=22), anoxia (13) or trauma (28) that occurred at least 12 months before enrollment, without contraindications to HBO2. Sixty-three participants enrolled in the study (21 females,42 males). Age was 45 +/- 16 years (18-76) and time from injury was 6.9 +/- 7.1 years (1.0-29.3). Fifty-three completed the study intervention, and 55 completed the assessment battery.PARTICIPANTS underwent 60 daily HBO2 sessions (1.5 atm abs, 100% oxygen, 60 minutes). Assessments were conducted at baseline, after the HBO2 course, and six months later.The prime outcome was feasibility. To estimate the immediate and long-term effects of HBO2, we assessed neuropsychological measures, questionnaires, neurologic exam and physical functioning measures. Some participants also had pre- and post-HBO2 speech evaluation (n=27) and neuroimaging (n=17).The study met our a priori definition for feasibility for recruitment, but 44% required additional time to complete the 60 sessions (up to 105 days). HBO2-related adverse events were rare and not serious. Although many participants reported improvement in symptoms (51% memory, 51% attention/concentration, 48% balance/coordination, 45% endurance, 20% sleep) post-HBO2, and 93% reported that they would participate in the study again, no standardized testing showed clinically important improvement. In the small subset of those undergoing neuroimaging, apparent improvement was observed in auditory functional MRI (8/13), MR spectroscopy (9/17) and brain perfusionby CT angiography (5/9).Conducting an HBO2 clinical trial in this population was feasible. Although many participants reported improvement, the lack of concurrent controls limits the strength of inferences from this trial, especially considering lack of change in standardized testing. The clinical relevance of neuroimaging changes is unknown. The findings of this study may indicate a need for caution when considering the broad application of HBO2 more than one year after brain injury due to stroke, severe TBI and anoxia, until there is more compelling evidence from carefully designed sham-controlled, blinded clinical trials.

Background Each year, more than 200 people in the United States die from carbon monoxide (CO) poisoning. Poisoning has occurred at motels, hotels, and resorts. Congressional mandate requires smoke alarms in all guest rooms; however, smoke alarms do not detect CO. Methods Data on patients poisoned at hotels, motels, and resorts were evaluated at a hyperbaric medicine service. In 2005, legal databases and online news databanks were searched to discover additional incidents. Only victims evaluated in hospitals or declared dead at the scene were included. Cases of intentional poisoning and poisoning from fires were excluded. Results Between 1989 and 2004, 68 incidents of CO poisoning occurring at hotels, motels, and resorts were identified, resulting in 772 accidentally poisoned: 711 guests, 41 employees or owners, and 20 rescue personnel. Of those poisoned, 27 died, 66 had confirmed sequelae, and 6 had sequelae resulting in a jury verdict. Lodging-operated, faulty room heating caused 45 incidents, pool/spa boilers 16, CO entrained from outdoors 5, and unreported sources caused 2 incidents. Public verdicts have averaged $4.8 million per incident (range, $1 million to $17.5 million). Poisoning occurred at hotels of all classes. Despite these incidents, most properties did not install CO alarms, and requirements for CO alarms at hotels, motels, and resorts are rare. Conclusions Guests of motels, hotels, and resorts remain at risk for injury or death from CO poisoning. Measures to prevent CO poisoning of guests and employees of the lodging industry should be evaluated.

Importance Improvement has been anecdotally observed in patients with persistent postconcussion symptoms (PCS) after mild traumatic brain injury following treatment with hyperbaric oxygen (HBO). The effectiveness of HBO as an adjunctive treatment for PCS is unknown to date. Objectives To compare the safety of and to estimate the efficacy for symptomatic outcomes from standard PCS care alone, care supplemented with HBO, or a sham procedure. Design, Setting, and Participants Multicenter, double-blind, sham-controlled clinical trial of 72 military service members with ongoing symptoms at least 4 months after mild traumatic brain injury enrolled at military hospitals in Colorado, North Carolina, California, and Georgia between April 26, 2011, and August 24, 2012. Assessments occurred before randomization, at the midpoint, and within 1 month after completing the interventions. Interventions Routine PCS care was provided in specialized clinics. In addition, participants were randomized 1:1:1 to 40 HBO sessions administered at 1.5 atmospheres absolute (ATA), 40 sham sessions consisting of room air at 1.2 ATA, or no supplemental chamber procedures. Main Outcomes and Measures The Rivermead Post-Concussion Symptoms Questionnaire (RPQ) served as the primary outcome measure. A change score of at least 2 points on the RPQ-3 subscale (range, 0-12) was defined as clinically significant. Change scores from baseline were calculated for the RPQ-3 and for the total RPQ. Secondary measures included additional patient-reported outcomes and automated neuropsychometric testing. Results On average, participants had sustained 3 lifetime mild traumatic brain injuries; the most recent occurred 23 months before enrollment. No differences were observed between groups for improvement of at least 2 points on the RPQ-3 subscale (25% in the no intervention group, 52% in the HBO group, and 33% in the sham group; P = .24). Compared with the no intervention group (mean change score, 0.5; 95% CI, −4.8 to 5.8; P = .91), both groups undergoing supplemental chamber procedures showed improvement in symptoms on the RPQ (mean change score, 5.4; 95% CI, −0.5 to 11.3; P = .008 in the HBO group and 7.0; 95% CI, 1.0-12.9; P = .02 in the sham group). No difference between the HBO group and the sham group was observed ( P = .70). Chamber sessions were well tolerated. Conclusions and Relevance Among service members with persistent PCS, HBO showed no benefits over sham compressions. Both intervention groups demonstrated improved outcomes compared with PCS care alone. This finding suggests that the observed improvements were not oxygen mediated but may reflect nonspecific improvements related to placebo effects. Trial Registration clinicaltrials.gov Identifier:NCT01306968