Article – 1 - Carbon monoxide poisoning
Title: A prospective, randomized clinical trial comparing two hyperbaric treatment protocols for carbon monoxide poisoning.
Authors: Hampson, NP; Dunford, RG; Ross, DE; Wreford-Brown, CE
Digital Object Identifier (or PMID etc): Nil
Keywords: Nil
Abstract: The optimal hyperbaric oxygen (HBO2) treatment protocol for acute carbon monoxide (CO) poisoning is unknown. This is indicated by one study that found 18 different protocols to treat CO poisoning by North American multiplace hyperbaric facilities. A pilot study was conducted to evaluate the feasibility of randomizing patients to different protocols and to determine whether any large differences in clinical outcome were present between the two most common protocols. Adult patients with accidental CO poisoning resulting in transient loss of consciousness, presentation to the emergency department within 12 hours, primary language English, high school education, and residence within 100 miles of the hyperbaric facility were recruited. Enrolled patients were randomized to one HBO2 treatment at 2.4 atmospheres absolute (atm abs) pressure with 90 minutes of 100% oxygen breathing vs. treatment by the US Air Force CO protocol (3.0 atm abs maximum pressure). A neurocognitive screening test was performed immediately after hyperbaric treatment and repeated 14-21 days later.
Results: From 1995 to 2002, 30 patients age 21 to 88 years were randomized, 18 to treatment at 2.4 atm abs and 12 to 3.0 atm abs. Average carboxyhemoglobin level for the population was 24.8 +/- 8.8% (mean +/- SD). Delay to hyperbaric treatment averaged 313 +/- 129 minutes. Neither variable was different between treatment groups. Six patients had abnormal neurocognitive testing immediately following hyperbaric treatment, 4 in the 2.4 atm abs group (22%) and 2 in the 3.0 atm abs group (17%) (P=0.71). One patient in each group demonstrated abnormality on delayed testing (p=0.75). One in each group did not return for follow-up.
Conclusion: It is feasible to randomize CO-poisoned patients to different hyperbaric treatment protocols. Determination of differences in efficacy between treatment protocols will require a large multicenter trial with the use of detailed neurocognitive testing.
Article – 2 - Carbon monoxide poisoning
Title: Hyperbaric treatment of patients with carbon monoxide poisoning in the United States.
Authors: Hampson, NB; Little, CE
Digital Object Identifier (or PMID etc): Nil
Keywords: Nil
Abstract: Hyperbaric oxygen (HBO2) is effective therapy for carbon monoxide (CO) poisoning. In recent years, many hyperbaric physicians in the US have felt that numbers of patients referred for treatment of CO poisoning have decreased. Further, since the 2002 Weaver et al study (5), there has been discussion regarding the best treatment protocol. This study was conducted to determine numbers of patients treated with HBO2 annually over the past decade in the US and whether there is a consensus about the number of treatments per patient. A survey was mailed to all US facilities listed in the 2001 UHMS Chamber Directory. Two subsequent mailings were sent to survey nonresponders, followed by telephone contacts.
Results: Of the 320 facilities listed in the directory, 10 were nonresponders, 26 had closed since publication and 80 do not treat CO poisoning, leaving 204 facilities. From 1992-2002, a total of 16,367 patients were treated with HBO2 for CO poisoning, an average of 1,488 +/- 121 patients/year (mean < or = SD). While the total number of patients treated annually did not decrease during the period studied, the number treated per facility did decline as a result of an increase in number of treating facilities. Only 46 facilities (23%) automatically give more than 1 hyperbaric treatment per CO-poisoned patient. Among those that do, 20 facilities (10%) give 3 treatments per patient. Conversely, 136 (67%) sometimes give more than one treatment and 12 facilities (8%) never retreat.
Conclusion: Approximately 1,500 CO-poisoned patients are treated with HBO2 in the US annually, a number that has remained relatively constant since 1992. The majority of facilities does not routinely give more than one hyperbaric treatment, but will give repetitive treatment in certain situations.
Article – 3 - Carbon monoxide poisoning
Title: Central nervous system oxygen toxicity during hyperbaric treatment of patients with carbon monoxide poisoning
Authors: Hampson, NB; Simonson, SG; Kramer, CC; Piantadosi, CA
Digital Object Identifier (or PMID etc): PMID: 8989851
Keywords: Nil
Abstract: Hyperbaric oxygen (HBO2) is associated with a recognized risk for clinical central nervous system (CNS) toxicity. The risk for oxygen convulsions during routine hyperbaric treatment of most routine conditions is extremely low. Previous observations have suggested that the incidence of CNS toxicity during HBO2 treatment for carbon monoxide (CO) poisoning may be increased, both because of CNS injury caused by the poisoning and because higher treatment pressures are often utilized for this condition. This study reviews data from 900 CO-poisoned patients treated with HBO2 at Virginia Mason and Duke University Medical Centers from 1987 to 1996. One-third of the patient population was treated at each of the three HBO2 treatment pressures most commonly utilized for CO intoxication in North American multiplace chambers. Patient characteristics were similar in all groups. Among the 300 consecutive patients treated at each pressure, there was one seizure at 2.45 atm abs (0.3%), nine seizures at 2.80 atm abs (2.0%), and six seizures at 3.00 atm abs. This difference is statistically significant (P = 0.032; Fisher's Exact Test).
Conclusion: The potential difference in seizure risk should be considered when selecting the HBO2 treatment pressure for CO poisoning.
Article – 4 - Carbon monoxide poisoning
Title: Brain computerized tomography after hyperbaric oxygen therapy for carbon monoxide poisoning
Authors: Pracyk, JB; Stolp, BW; Fife, CE; Gray, L; Piantadosi, CA
Digital Object Identifier (or PMID etc): PMID: 7742705
Keywords: Nil
Abstract: The role of brain computerized tomography (CT) imaging in predicting clinical outcome was investigated in patients receiving hyperbaric oxygen therapy for serious carbon monoxide (CO) poisoning. From a series of 48 consecutive patients suffering loss of consciousness from CO exposures, the records of 40 selected patients were evaluated to determine how their CT findings correlated with clinical outcome. A neuroradiologist blinded to patient outcome confirmed the radiographic findings. CT abnormalities consisted of globus pallidus hypodensities (nine patients), subcortical white matter hypodensities (four), cerebral cortical lesions (one), cerebral edema (one), hippocampal lesions (one), and complete loss of gray-white differentiation (one). Of the patients with globus pallidus lesions, 44% manifested incomplete recovery, whereas white matter lesions reflected a 74% incidence of morbidity. Age, duration of CO exposure, and interval between CO exposure and treatment did not significantly relate to clinical outcome. The blood carboxyhemoglobin levels correlated with clinical prognosis (P < 0.05) and, importantly, CT results significantly predicted clinical outcome (P < 0.05). A normal scan correlated highly with a complete recovery, whereas an abnormal scan predicted incomplete recovery or death, despite prior HBO therapy.
Conclusion: The current study establishes prognostic validity for brain CT imaging for evaluating clinical outcome after HBO therapy for CO poisoning.
Article – 5 - Carbon monoxide poisoning
Title: Effects of hyper baric treatment on carbon monoxide elimination in humans
Authors: Britten, JS; Myers, RA
Digital Object Identifier (or PMID etc): PMID: 4082346
Keywords: Carbon Monoxide/*blood, Carbon Monoxide Poisoning/*blood/therapy Comparative Study Human *Hyperbaric Oxygenation Kinetics Metabolic Clearance Rate Oxygen Inhalation Therapy
Abstract: A theoretical model of carbon monoxide elimination from the acutely poisoned individual is presented. The model is derived from a one-compartment system with the rate-limiting step that of alveolar ventilation, assuming equilibration of carbon monoxide and oxygen between alveolar gas and pulmonary capillary blood and incorporates the effect of the carboxyhemoglobin-oxyhemoglobin equilibrium in the pulmonary capillary.
Conclusion: The model is applied to groups of patients treated for carbon monoxide intoxication both by conventional means and by hyperbaric medicine and to some animal studies found in the literature with satisfactory fit of data to the model. Finally, a number of factors responsible for the variability of CO elimination are discussed in terms of the model.
Article – 6 - Carbon monoxide poisoning
Title: Normobaric and hyperbaric oxygen treatment of acute carbon monoxide poisoning in rats
Authors: Jiang, J; Tyssebotn, I
Digital Object Identifier (or PMID etc): PMID: 9171469
Keywords: Nil
Abstract: Based on a model of acute carbon monoxide (CO) poisoning in rats with an occluded left carotid artery, we have evaluated the effects of normobaric oxygen (NBO2) and hyperbaric oxygen (HBO2) on mortality and morbidity. After exposure to 2,700 ppm CO in air for 1 h, the rats were grouped and treated with air (group 1, untreated controls, in a previous study), 100 kPa O2 for 4 h (group 2), 300 kPa normoxia (group 3, pressure controls), and 300 kPa O2 (group 4) for 1 h, respectively. NBO2 started immediately, whereas HBO2 began 35 min after the end of the CO exposure. At the termination of the exposure, the four groups suffered identical levels of poisoning as indicated by the degrees of hypothermia, hypocapnia, drop in mean arterial pressure, and acidosis. Up to 48 h after the end of the CO exposure, mortalities were 76, 58, 75, and 17 in groups 1-4, respectively. The neurologic morbidities, indicated by abnormal motor behaviors and edema in the left cerebral hemispheres, were 84, 67, 83, and 42% in groups 1-4, respectively.
Conclusion: Compared to the normoxic treatments, the HBO2, but not the NBO2, significantly reduced the mortality and the neurologic morbidity. HBO2 was also significantly better than NBO2 in increasing surviving time and survival rate. The results support the value of HBO2 in improving short-term outcome of acute CO poisoning in this rat model.
Article – 7 - Carbon monoxide poisoning
Title: Non-comatose patients with acute carbon monoxide poisoning: hyperbaric or normobaric oxygenation?
Authors: Ducasse, JL; Celsis, P; Marc-Vergnes, JP
Digital Object Identifier (or PMID etc): PMID: 7742714
Keywords: Nil
Abstract: Twenty-six non-comatose patients with acute carbon monoxide (CO) poisoning were randomized into two groups. Both groups were treated as soon as possible and for 2 h, the first group by 100% normobaric oxygen (NBO) and the second by 100% hyperbaric oxygen. At the end of this period, patients treated by HBO had a significant improvement of their clinical and biological conditions compared with patients treated with NBO. Both groups then received the same NBO therapy for 10 h. At the end of this second period, carboxyhemoglobin level was normal in both groups. However, patients treated with NBO showed some clinical impairments, and 3 wk after onset had significantly more electroencephalogram abnormalities and a reduced cerebral blood flow reactivity to acetazolamide.
Conclusion: We conclude that HBO reduces the time of initial recovery and the number of delayed functional abnormalities in non-comatose patients with acute CO poisoning. A practical scheme for the use of NBO and HBO in such patients is proposed.
Article – 8 - Carbon monoxide poisoning
Title: Hyperbaric oxygen ameliorates delayed neuropsychiatric syndrome of carbon monoxide poisoning.
Authors: Chang, DC; Lee, JT; Lo, CP; Fan, YM; Huang, KL; Kang, BH; Hsieh, HL; Chen, SY
Digital Object Identifier (or PMID etc): Nil
Keywords: Nil
Abstract: Delayed neuropsychiatric syndrome (DNS) is characterized by mental impairment, motor dysfunction, dementia, or psychosis that develops between a few days and weeks after acute carbon monoxide (CO) poisoning. One possible mechanism responsible for CO-mediated encephalopathy involves oxidative stress, such as lipid peroxidation, caused by the cellular uptake of CO and which leads to an inflammatory cascade. There is no current effective treatment for DNS. We applied 8-40 sessions of hyperbaric oxygen therapy (HBO2) to patients with DNS and evaluated its effectiveness. After admission, all patients were administered piracetam or bromocriptine, or both, and received HBO2. Neuropsychiatric tests included EEG, mini-mental status examination (MMSE), brain MRI, event-related potential (ERP), and brain perfusion scan (brain SPECT). Results of these tests were compared before and after HBO2, and the clinical features were monitored during this period.
Results: The symptoms of DNS for all patients improved significantly after HBOT. Although white matter changes remained evident in the brain MRI scans, other examinations such as EEG, MMSE, ERP, and 99mTc-ECD brain SPECT were nearly normal after HBOT.
Conclusion: Our results suggest that HBO2 decreases the severity of impairment in patients with DNS. Although a large randomized trial is required to address the efficacy of this therapy, therapeutic application of HBO2 may be recommended in patients with DNS after CO poisoning.
Article – 9- Carbon monoxide poisoning
Title: Cerebrospinal fluid pressure changes after acute carbon monoxide poisoning and therapeutic effects of normobaric and hyperbaric oxygen in conscious rats
Authors: Jiang, J; Tyssebotn, I
Digital Object Identifier (or PMID etc): PMID: 9444057
Keywords: Nil
Abstract: This study on conscious rats with occluded left carotid artery investigates the influence of cerebral edema after acute carbon monoxide (CO) poisoning on cerebrospinal fluid pressure (CSFp) and evaluates the therapeutic effectiveness of normobaric oxygen (NBO2) and hyperbaric oxygen (HBO2). The CSFp was continuously recorded via a cannula placed in the left cerebral ventricle before, during, and for up to 6 h after exposure to 0.27% CO for 1 h. A non-sustained small increase in the CSFp and identical degrees of hypoxemia, hypocapnia, arterial hypotension, and acidosis were found during the exposure in all rats. After the CO exposure, all non-edema control rats without carotid artery ligation (n = 7) recovered completely with normal CSFp, behavior, and brain water content. All untreated (n = 7) and NBO2-treated rats (n = 7) developed a severely increased CSFp (> 50 mmHg) with neurologic motor dysfunction, and died of a severely increased CSFp (> 100 mmHg) with considerable cerebellar herniation. Except in one rat, the CSFp did not reach a dangerous level (> 25 mmHg) after the HBO2 session (300 kPa O2 for 1 h, beginning at 20 min post CO). All HBO-treated rats (n = 7) survived with less neurologic motor dysfunction and less left hemispheric edema than those in untreated and NBO2-treated rats.
Conclusion: The results demonstrated that the increase in the CSFp was related to the left hemispheric edema, and that the cerebellar herniation was the predominant cause of death after the CO exposure. HBO2, but not NBO2, prevented the severe increase in the CSFp and thus saved the life after the CO exposure.
Article – 10 - Carbon monoxide poisoning
Title: Treatment of Carbon Monoxide Poisonings in Multiplace Hyperbaric Chambers.
Authors: Hampson, NB; Dunford, RG; Norkool, DM
Digital Object Identifier (or PMID etc): Nil
Keywords: carbon monoxide poisoning, hyperbaric ayvgen tljerapy, multiplace hyperbaric chambers
Abstract: To determine the frequency and type of hyperbaric treatments administered for carbon monoxide (CO) poisoning in North America, we surveyed all multiplace hyperbaric facilities listed in the 1990 UHMS Chamber Directory. In 1990,42 facilities treated 1023 CO poisonings, with 38 U.S. chambers treating 832 patients and 4 Canadian chambers treating 191 patients. Individ¬ual facilities treated from 1 to 93 patients in that year. A total of 18 different hyperbaric protocols are used at these facilities for primary treatment of CO poisoning. These include 3 protocols with a maximum pressure of 3 0 atm abs, 13 protocols with a maximum pressure of 2.8 atm abs, and 2 protocols with a maximum pressure of 2.4-2.5 ami abs. In 1990, 284 patients were treated at facilities utilizing 3 0 atm abs, 561 at facilities utilizing 2.8 atm abs, and 178 at facilities utilizing 2.4-2.5 atm abs. Among treating facilities, 24% never re-treat patients for the same episode of CO poisoning. With regard to pregnancy, 31 of 42 chambers have treated or would treat pregnant patients with significant CO intoxication. Among these, 28 utilize the same primary treatment protocol as for non-pregnant patients.
Conclusion: In summary, a large number of CO poisonings are treated in North American multiplace chambers annually, utilizing a wide variety' of treatment profiles.