A randomized trial of one versus three hyperbaric oxygen sessions for acute carbon monoxide poisoning.

Introduction: Hyperbaric oxygen (HBO2) improves outcome in patients with acute carbon monoxide (CO) poisoning, but optimal dose/timing are unknown. In this double-blind, sham-controlled randomized trial, we compared neuropsychological sequelae at six weeks and six months in patients receiving three HBO2 sessions or one HBO2 session and two sham chamber sessions after acute CO poisoning. Methods: After completing one HBO2 session (3.0 ATA, 60 minutes, 2.0 ATA, 65 minutes), CO-poisoned patients were randomized (1:1): two sham chamber sessions (1 ATA air, 120 minutes) or two additional HBO2sessions (2.0 ATA, 90 minutes at pressure, 120 minutes in chamber) completed within 24 hours. Eligible patients were >24 hours from accidental poisoning, English-speaking, and not intubated. We planned 150 participants. Results: The study was stopped early for enrollment futility. From 2006 to 2016, we screened 395 patients: 136 were deemed eligible to participate, and 75 signed informed consent. Two were later withdrawn for past brain injury/PTSD (one sham, one HBO2), and one for performance validity (sham). Of the 72 analyzed, mean age was 42 ± 15 years, 40 (56%) were male, 20 (28%) had loss of consciousness, and mean initial carboxyhemoglobin was 22 ± 9%. The rate of six-week neuropsychological sequelae was 50% in the one-HBO2 session group and 55% in the three-HBO2 sessions group (p = 0.80), and at six months was 42% versus 46%, respectively (p = 0.76). Conclusions: There was no difference in the rate of neuropsychological sequelae in those who received three HBO2 sessions and those who received one HBO2 sessions and two sham sessions. The higher rate of neuropsychological sequelae compared to an earlier study may be due to neuropsychological test-retest effects or previously identified risk factors for cognitive sequelae (age, duration of poisoning, cerebellar dysfunction). This study's rates of cognitive difficulties, affective complaints, and other symptoms suggest brain injury after CO poisoning is common.

Three cases of clinically significant inaccurate carboxyhemoglobin measurement.

Background: Clinicians often rely on measurement of carboxyhemoglobin (COHb) to confirm or rule out a diagnosis of carbon monoxide (CO) poisoning. Methods: 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. Results: 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%). Conclusions: 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.

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.

Patterns of cardiac dysfunction after carbon monoxide poisoning.

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 (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. Conclusion: 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.

Reference ranges and stability of auditory and vestibular measures in a comprehensive assessment battery for traumatic brain injury.

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.

Hidden hearing deficits in military service members with persistent post concussive symptoms.

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.

Prospective study of anxiety, post-traumatic stress and depression on postural control, gait, otolith and visuospatial function in military service members with persistent post-concussive symptoms.

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, post-traumatic 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. CONCLUSION: 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.

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).

Myositis associated with carbon monoxide poisoning.

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. Conclusion: 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).

Quantitative analysis tool for clinical functional MRI in mild traumatic brain injury.

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.

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.

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.

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.

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.

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.

Performance of three large-volume infusion pumps with the monoplace hyperbaric chamber.

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.

Inaccurate pulse CO-oximetry of carboxyhemoglobin due to digital clubbing: case report.

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.

Carbon monoxide poisoning in Utah: 1996-2013.

INTRODUCTION: The true incidence of carbon monoxide (CO) poisoning is not clearly known, but a description of possible trends could aid in prevention. METHODS: Investigators searched Utah state databases for emergency department (ED) visits and admissions for CO poisoning and medical examiner records for CO-related fatalities. RESULTS: 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%). CONCLUSIONS: 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.

Blue-fingered diver: case report.

Although Raynaud's phenomenon is a well-known consequence of exposure to cold, neither its incidence in recreational divers nor case reports in that population have been reported in the medical literature. We present a case report of the initial manifestation of primary Raynaud's phenomenon during a warm-water scuba dive. A healthy 18-year-old Caucasian male made four open-circuit compressed air scuba dives over two days in the Florida Keys to a maximum depth of 90 feet. After two of those dives, he noted painless, blue discoloration on three digits of his left hand, unaccompanied by sensory changes, which resolved within an hour of surfacing. During a fitness-to-dive evaluation one week later, his physical examination was normal. No skin discoloration, neurological symptoms or changes to pulse or blood pressure were noted with temperature or positional provocation. Laboratory testing was normal. However, arterial Doppler measurements were severely diminished in all digits of both upper extremities with temperature provocation, and continued to be diminished five minutes after immersion, suggesting Raynaud's phenomenon.