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 Two were later withdrawn for past brain injury/PTSD (one sham, one HBO₂), and one for performance validity (sham).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.

Long-term effects of carbon monoxide poisoning at Miike coal mine: A 33-year follow-up study

On November 9, 1963, a coal dust explosion occurred at the Miike Mikawa Coal Mine (Omuta, Kyushu Region of Japan). This resulted in a massive release of carbon monoxide (CO) gas that resulted in 458 fatalities and 839 victims of CO poisoning. After the accident, the Department of Neuropsychiatry, Kumamoto University School of Medicine (including the authors) immediately began to conduct periodic medical examinations of the victims. Such a long-term follow up of so many CO-poisoned patients is globally unprecedented. When the Miike Mine was closed in March of 1997, 33 years after the disaster, we conducted the final follow-up study.

Severe carbon monoxide poisonings in scuba divers: Asia-Pacific cases and causation

AIM

Reports of fatal incidents in recreational scuba divers from carbon monoxide (CO) poisoning are rare. This study aimed to identify scuba fatalities in the Asia-Pacific region caused by breathing-gas contamination to better understand the likely sources of contamination and reduce such preventable deaths.

METHODS

A hand search of Project Stickybeak reports, subsequent Australian fatality series reports, and of published New Zealand diving fatality reports and associated data was conducted, as well as key word searches of the National Coronial Information System for scuba fatalities in Australia and New Zealand. Cases identified were matched with the Australasian Diving Safety Foundation diving fatality database. Available reports were examined.

RESULTS

Four scuba deaths resulting from CO poisoning were identified from 645 scuba fatalities, including one report from each of Australia, New Zealand, Singapore, and the Maldives. A near-fatal incident was also identified in Indonesia. Two of the fatal incidents and the near-fatal incident involved internal combustion engine exhaust gases from the compressor system or elsewhere entering the air intake. Two deaths likely resulted from combustion within compressor systems.

CONCLUSIONS

Scuba fatalities from CO poisoning are uncommon, albeit likely under-reported. Sources of CO include exhaust gases entering the compressor and CO production by pyrolysis or gasification within the compressor or its filter system. Preventive measures include proper installation (including positioning of the air intake relative to combustion exhaust), appropriate maintenance, fitting of pressure-maintaining valves and avoidance of overheating. Formal training of compressor operators, improved diver education, mandatory requirements for installation compliance assessments, safety inspections, and the use of carbon monoxide alarms are recommended.

Neurological symptoms improved by hyperbaric oxygen therapy in a post-cardiac arrest patient due to carbon monoxide poisoning: a case report

BACKGROUND

Carbon monoxide (CO) poisoning and cardiac arrest can cause neurological complications such as mental deterioration and movement disorders through ischemic brain injury. We report a case in which neurological sequelae after cardiac arrest caused by CO poisoning improved after hyperbaric oxygen (HBO2) therapy.

CASE REPORT

A 43-year-old male visited the hospital with cardiac arrest due to CO poisoning. He developed neurological sequelae including mental deterioration and myoclonus after recovering spontaneous circulation. Anticonvulsant therapy was used after target temperature management but did not have a positive effect on neurological symptoms. However, after HBO2 therapy the patient's neurological symptoms improved, and he was discharged a month later.

CONCLUSION

HBO2 therapy may be considered when neurological sequelae persist after cardiac arrest due to CO poisoning.

Repetitive hyperbaric oxygen therapy for paroxysmal sympathetic hyperactivity after acute carbon monoxide poisoning

Delayed neuropsychological sequelae (DNS) are relatively common complications of acute carbon monoxide (CO) poisoning, and usually develop within several days to weeks after the initial clinical recovery from acute CO poisoning. DNS can consist of various symptoms such as memory loss, confusion, ataxia, seizures, urinary incontinence, fecal incontinence, emotional lability, disorientation, hallucinations, mutism, cortical blindness, psychosis, parkinsonism, gait disturbances, rigidity, bradykinesia, and other motor disturbances. Paroxysmal sympathetic hyperactivity (PSH) is a potentially life-threatening disease secondary to acute acquired brain injury. It is characterized by episodic and simultaneous paroxysmal increases in sympathetic and motor activities, not rare in patients with a severe traumatic brain injury. The term PSH is clinically more accurate than the previously used ones describing such conditions as non-stimulated tachycardia, hypertension, tachypnea, hyperthermia, external posturing, diaphoresis, and paroxysmal autonomic instability with dystonia. Development of PSH typically prolongs the length of hospital stay and potentially leads to a secondary brain injury or even death. To date, the occurrence of PSH in the DNS after acute CO poisoning has not been reported in the literature. Potential mechanisms underlying the development of DNS in the deep white matter of the brain are immune-related inflammation and vasodilatation. Repetitive hyperbaric oxygen therapy, combined with methylprednisolone administration, may inhibit DNS progression by inducing cerebral oxygenation, inhibiting inflammation, and reducing cerebral edema. Herein, we report three cases in which the patients recovered from the PSH as DNS after CO poisoning after receiving repetitive hyperbaric oxygen therapy.

Performance characteristics of high-frequency percussive ventilation under hyperbaric conditions

INTRODUCTION

Safe administration of critical care hyperbaric medicine requires specialized equipment and advanced training. Equipment must be tested in order to evaluate function in the hyperbaric environment. High-frequency percussive ventilation (HFPV) has been used in intensive care settings effectively, but it has never been tested in a hyperbaric chamber.

METHODS

Following a modified U.S. Navy testing protocol used to evaluate hyperbaric ventilators, we evaluated an HFPV transport ventilator in a multiplace hyperbaric chamber at 1.0, 1.9, and 2.8 atmospheres absolute (ATA). We used a test lung with analytical software for data collection. The ventilator uses simultaneous cyclic pressure-controlled ventilation at a pulsatile flow rate (PFR)/oscillatory continuous positive airway pressure (oCPAP) ratio of 30/10 with a high-frequency oscillation percussive rate of 500 beats per minute. Inspiratory and expiratory times were maintained at two seconds throughout each breathing cycle.

RESULTS

During manned studies, the PFR/oCPAP ratios were 26/6, 22/7, and 22.5/8 at an airway resistance of 20cm H2O/L/second and 18/9, 15.2/8.5, and 13.6/7 at an airway resistance of 50 cm/H2O/L/second at 1, 1.9, and 2.8 ATA. The resulting release volumes were 800, 547, and 513 mL at airway resistance of 20 cm H2O/L/sec and 400, 253, and 180 mL at airway resistance of 50 cm/H2O/L/sec at 1, 1.9, and 2.8 ATA. Unmanned testing showed similar changes. The mean airway pressure (MAP) remained stable throughout all test conditions; theoretically, supporting adequate lung recruitment and gas exchange. A case where HFPV was used to treat a patient for CO poisoning was presented to illustrate that HFPV worked well under HBO2 conditions and no complications occurred during HBO2 treatment.

CONCLUSION

The HFPV transport ventilator performed adequately under hyperbaric conditions and should be considered a viable option for hyperbaric critical care. This ventilator has atypical terminology and produces unique pulmonary physiology, thus requiring specialized training prior to use.

Carbon monoxide poisoning

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

Carbon monoxide poisoning while scuba diving: a rare event?

Contamination of breathing gas is a risk for all divers. Some hydrocarbon contaminants will be sensed by the diver and the dive profile aborted. On the contrary, carbon monoxide may not be recognized by the diver and catastrophic consequences can result. Reported here is the fatal case of carbon monoxide poisoning while scuba diving, an event that has rarely been reported in the medical literature. A detailed review of other published cases of CO poisoning while scuba diving is included, attempting to identify causes in common and propose methods of prevention.

Racial and ethnic trends in unintentional carbon monoxide poisoning deaths

OBJECTIVE

Government programs have attempted to impact a recognized elevated risk for carbon monoxide (CO) poisoning among minority racial and ethnic groups. This study sought to describe U.S. mortality due to unintentional, non-fire-related CO poisoning, examining the distribution and trends by race and ethnicity.

METHODS

CDC Wonder was used to extract and analyze data on all U.S. resident deaths from unintentional CO poisoning from 2000-2017, categorizing them by year, race, ethnic origin and gender.

RESULTS

The absolute number of unintentional CO deaths decreased from about 450 to 380 per year during the period studied, a number near totally accounted for by the decrease in deaths occurring among non-Hispanic/Latino whites. The number of deaths among the remainder of the population did not significantly change. However, greater growth in minority populations resulted in a similar decline in the mortality rate between non-Hispanic/Latino whites and the combined minority population. The decline in combined minority death rate resulted from a decrease in the Hispanic/Latino white rate. Death rate did not decline in the black or African American population.

CONCLUSIONS

All minority groups continue to display a disproportionate number of unintentional non-fire-related CO poisoning deaths compared to non-Hispanic/Latino whites. The decrease in U.S. deaths from unintentional non-fire-related carbon monoxide poisoning from 2000-2017 is accounted for by a decrease in non-Hispanic/Latino white deaths. While numbers of such deaths among minority groups have not changed since 2000, increases in the size of minority populations have resulted in a declining crude death rate for Hispanic/Latino whites.

Atrial fibrillation associated with carbon monoxide poisoning

Carbon monoxide intoxication occurs usually via inhalation of carbon monoxide that is emitted as a result of a fire, furnace, space heater, generator, motor vehicle. A 37-year-old male patient was admitted to the emergency department at about 5:00 a.m., with complaints of nausea, vomiting and headache. He was accompanied by his wife and children. His venous blood gas measures were: pH was 7.29, partial pressure of carbon dioxide (pCO2) was 42 mmHg, partial pressure of oxygen (pO2) was 28 mmHg, carboxyhemoglobin (COHb) was 12.7% (reference interval: 0.5%-2.5%) and oxygen saturation was 52.4%. Electro-cardiogram (ECG) examination showed that the patient was not in sinus rhythm but had atrial fibrillation. After three hours the laboratory examination was repeated: Troponin was 1.2 pg/ml and in the arterial blood gas COHb was 3%. The examination of the findings on the monitor showed that the sinus rhythm was re-established. The repeated ECG examination confirmed the conversion to sinus rhythm. He was monitored with the normobaric oxygen administration.

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).

Hyperbaric oxygen therapy decreases QTc dispersion that increased in CO poisoning

Myocardial injury is a frequent consequence of moderate to severe CO (carbon monoxide) poisoning and a significant predictor of mortality in CO injury. Electrocardiography (ECG) is an easily accessible diagnostic tool for evaluating myocardial damage. Increased QT interval and QT dispersion are related to heterogeneity of regional ventricular repolarization and can develop into arrhythmias. It has been reported that QT interval and QT dispersion increase in patients with CO poisoning. Hyperbaric oxygen (HBO2) therapy has been used successfully in treating patients with CO poisoning. The aim of this study was to investigate change of corrected QT (QTc) interval and QTc dispersion after HBO2 therapy. This study included 31 patients with CO poisoning. QTc dispersion increased in patients with CO poisoning. The mean QTc dispersion was 54.94 milliseconds (ms) on admission. The mean QTc dispersion decreased to 35.74 ms after HBO2 therapy (P=0.003). There was also a correlation between carboxyhemoglobin level and QTc dispersion (P=0.029). HBO2 therapy, which decreases QTc dispersion, may improve the myocardial electrical homogeneity and reduce the risk of ventricular arrhythmia and cardiac death. Physicians should be aware of the effect of HBO2 therapy on myocardial damage when treating patients with CO poisoning. The ECGs should be examined carefully before referring or excluding HBO2 therapy.

Compartment syndrome in the forearm related to carbon monoxide intoxication: case report

INTRODUCTION

Carbon monoxide (CO) poisoning is one of the most common forms of intoxication around the world. One of the complications associated with CO exposure is direct toxicity to the skeletal muscles. Though compartment syndrome induced by CO intoxication is rare, it is a well-known complication. In this study, we present a case of CO poisoning in a patient who developed compartment syndrome in his forearm.

CASE REPORT

A 22-year-old man was found unconscious in a motel where a briquette had burned. He was later diagnosed with rhabdomyolysis associated with CO poisoning. After he regained consciousness, he experienced difficulty in moving his left arm, with sensory impairment in the same arm. He was diagnosed with compartment syndrome, and an emergency fasciotomy was performed. One month later, electromyography was performed which revealed left median, ulnar, radial, and musculocutaneous nerve palsy.

DISCUSSION

Compartment syndrome induced by CO intoxication is rare but is a well-known complication. Compartment syndrome is a limb-threatening and life-threatening condition. If untreated, the pressure in the muscle may rise, which can lead to tissue necrosis. Generally, nerve paralysis does not occur in CO poisoning. In our case, it occurred as median, ulnar, radial and musculocutaneous nerve palsy.

CONCLUSION

Side effects of CO poisoning can be extant, especially for those who are unconscious since they cannot express pain, numbness, and motor weakness. It is important to not overlook compartment syndrome, to double-check whether there is swelling, change in skin color, or skin firmness in extremities, and to observe the patient closely.

Carboxyhemoglobin: a primer for clinicians

One of carbon monoxide's several mechanisms of toxicity is binding with circulating hemoglobin to form carboxyhemoglobin, resulting in a functional anemia. While patients with carbon monoxide poisoning are often said to be "cherry-red," such discoloration is rarely seen. Carboxyhemoglobin levels cannot be measured with conventional pulse oximetry, can be approximated with pulse CO-oximetry, and are most accurately measured with a laboratory CO-oximeter. Carboxyhemoglobin levels are quite stable and can be accurately measured on a transported blood sample. For clinical purposes, arterial and venous carboxyhemoglobin levels can be considered to be equivalent. Carboxyhemoglobin levels are typically lower than 2% in non-smokers and lower than 5% in smokers. A level over 9% is almost always due to exogenous carbon monoxide exposure, even among smokers. Conversely, a low level does not exclude significant exposure under certain circumstances. As carboxyhemoglobin levels of poisoned patients do not correlate with symptoms or outcome, their greatest utility is a marker of exposure.

Hemiplegia and bilateral globus pallidus infarcts after carbon monoxide poisoning: case report

The vast clinical manifestations of carbon monoxide (CO) poisoning can involve the neurological, neuropsychological and cardiac systems as well as others. In this case report, we describe our management of a 64-year-old woman exposed to CO in her apartment. Her presentation was unusual in that she had symmetric globus pallidus lesions, no evidence of thrombosis, but the lateralizing neurologic manifestation of severe hemiplegia.

Hyperbaric oxygen for late sequelae of carbon monoxide poisoning enhances neurological recovery: case report

Neuropsychiatric sequelae have been reported in 15%-45% of survivors of carbon monoxide (CO) poisoning. Hyperbaric oxygen (HBO₂) therapy reduces the incidence of cognitive and neurological a dysfunction. The efficacy of providing HBO₂ beyond the first one to two days after initial insult is unknown. However, some evidence exists for the benefit of this treatment. We report on treating a patient 14 months after CO injury, who responded with markedly improved neurologic status. A 27-year-old scholar was found comatose due to CO poisoning (carboxyhemoglobin = 31.7%). He received five acute HBO₂ treatments. After discharge, he developed chorea, Parkinsonism, dystonia, memory loss, slowed processing speed and verbal fluency, leaving him disabled. After the patient reached a clinical plateau, HBO₂ was tried again at 90 minutes at 2.4 ATA plus air breaks. Neuropsychological testing was performed at baseline and after each 20 HBO₂ cycles, five of which were performed during the period from 14-22 months after CO exposure. After the first 20 treatments, Parkinsonism and dystonia improved. After 40 sessions, further improvements were seen on mental speed, verbal fluency, and fine motor movements. The outcome following 100 treatments was that the patient regained independence, including the ability to drive and to become gainfully employed. Our case calls into question the concept that HBO₂ therapy has no role during the chronic phase of CO brain injury. Randomized clinical trials should be considered to evaluate the therapeutic efficacy of HBO₂ in patients with neurological sequelae following CO injury.