Accuracy of Noninvasive Multiwave Pulse Oximetry Compared With Carboxyhemoglobin From Blood Gas Analysis in Unselected Emergency Department Patients

Diagnosis of carbon monoxide exposure in clinical research and practice: A scoping review

OBJECTIVE

To undertake a scoping review to identify methods and diagnostic levels used in determining unintentional, non-fire related carbon monoxide exposure.

DESIGN

Online databases and grey literature were searched from 1946 to 2023 identifying 80 papers where carbon monoxide levels were reported.

RESULTS

80 papers were included; 71 research studies and 9 clinical guidelines. Four methods were described: blood carboxyhaemoglobin (arterial or venous blood analysis), carbon monoxide oximetry (SpO2), expired carbon monoxide, and ambient carbon monoxide sampling. Blood analysis methods predominated (60.0% of the papers). Multiple methods of measurement were used in 26 (32.5%) of the papers. Diagnostic levels for carboxyhaemoglobin were described in 54 (67.5%) papers, ranging between 2% and 15%. 26 (32.5%) papers reported diagnostic levels that were adjusted for the smoking status of the patient.

CONCLUSIONS

Four methods were found for use in different settings. Variability in diagnostic thresholds impairs diagnostic accuracy. Agreement on standardised diagnostic levels is required to enable consistent diagnosis of unintentional, non-fire related carbon monoxide exposure.

Correlation between Carboxyhemoglobin Levels Measured by Blood Gas Analysis and by Multiwave Pulse Oximetry

Carbon monoxide (CO) poisoning is difficult to diagnose owing to its nonspecific symptoms. Multiwave pulse oximetry can be used to quickly screen patients for CO poisoning. However, few studies have analyzed patients with CO poisoning who presented to the emergency department (ED). The primary aim of our study was to determine the correlation between COHb levels measured in blood gas analysis and COHb levels measured in multiwave pulse oximetry. Secondary aims were the sensitivity and specificity of the COHb level cutoff value using multiwave pulse oximetry to predict a 25% COHb level in blood gas analysis. This single-center retrospective observational study included patients with CO poisoning who visited the ED of a university-affiliated hospital in Seoul, Korea between July 2021 and June 2023. COHb poisoning was determined using blood gas analysis and multiwave pulse oximetry. The correlation of COHb levels between the two tests was evaluated using correlation analysis. The area under the receiver operating characteristic curve (AUC) of multiwave pulse oximetry was calculated to predict COHb levels from the blood gas analysis. The optimal cutoff values, sensitivity, and specificity of COHb were determined. A total of 224 patients who had COHb levels measured using both multiwave pulse oximetry and blood gas analysis were included in the analysis. In the correlation analysis, COHb showed a high positive correlation with COHb measured using blood gas analysis (Spearman correlation coefficient = 0.86, p < 0.001). The AUC of COHb measured by multiwave pulse oximetry to predict 25% of the COHb level (which can be an indication of hyperbaric oxygen treatment) measured by blood gas analysis was 0.916. When the COHb levels measured with multiwave pulse oximetry were 20% the sensitivity was 81% and the specificity was 83%, and when the COHb levels were 25% the sensitivity was 50% and the specificity was 95%. The COHb value measured using multiwave pulse oximetry blood gas analysis showed a high correlation. However, additional research using large-scale studies is required for validation.

Evaluation of a Portable Blood Gas Analyzer for Prehospital Triage in Carbon Monoxide Poisoning: Instrument Validation Study

BACKGROUND

Carbon monoxide (CO) poisoning is an important cause of morbidity and mortality worldwide. Symptoms are mostly aspecific, making it hard to identify, and its diagnosis is usually made through blood gas analysis. However, the bulkiness of gas analyzers prevents them from being used at the scene of the incident, thereby leading to the unnecessary transport and admission of many patients. While multiple-wavelength pulse oximeters have been developed to discriminate carboxyhemoglobin (COHb) from oxyhemoglobin, their reliability is debatable, particularly in the hostile prehospital environment.

OBJECTIVE

The main objective of this pilot study was to assess whether the Avoximeter 4000, a transportable blood gas analyzer, could be considered for prehospital triage.

METHODS

This was a monocentric, prospective, pilot evaluation study. Blood samples were analyzed sequentially with 2 devices: the Avoximeter 4000 (experimental), which performs direct measurements on blood samples of about 50 µL by analyzing light absorption at 5 different wavelengths; and the ABL827 FLEX (control), which measures COHb levels through an optical system composed of a 128-wavelength spectrophotometer. The blood samples belonged to 2 different cohorts: the first (clinical cohort) was obtained in an emergency department and consisted of 68 samples drawn from patients admitted for reasons other than CO poisoning. These samples were used to determine whether the Avoximeter 4000 could properly exclude the diagnosis. The second (forensic) cohort was derived from the regional forensic center, which provided 12 samples from documented CO poisoning.

RESULTS

The mean COHb level in the clinical cohort was 1.7% (SD 1.8%; median 1.2%, IQR 0.7%-1.9%) with the ABL827 FLEX versus 3.5% (SD 2.3%; median 3.1%, IQR 2.2%-4.1%) with the Avoximeter 4000. Therefore, the Avoximeter 4000 overestimated COHb levels by a mean difference of 1.8% (95% CI 1.5%-2.1%). The consistency of COHb readings by the Avoximeter 4000 was excellent, with an intraclass correlation coefficient of 0.97 (95% CI 0.93-0.99) when the same blood sample was analyzed repeatedly. Using prespecified cutoffs (5% in nonsmokers and 10% in smokers), 3 patients (4%) had high COHb levels according to the Avoximeter 4000, while their values were within the normal range according to the ABL827 FLEX. Therefore, the specificity of the Avoximeter 4000 in this cohort was 95.6% (95% CI 87%-98.6%), and the overtriage rate would have been 4.4% (95% CI 1.4%-13%). Regarding the forensic samples, 10 of 12 (83%) samples were positive with both devices, while the 2 remaining samples were negative with both devices.

CONCLUSIONS

The limited difference in COHb level measurements between the Avoximeter 4000 and the control device, which erred on the side of safety, and the relatively low overtriage rate warrant further exploration of this device as a prehospital triage tool.

Diagnostic accuracy of carboxyhemoglobin saturation with pulse CO-oximetry in patients with carbon monoxide poisoning

Objective

Carboxyhemoglobin saturation (SpCO)with pulse CO-oximetry is an alternative method in CO poisoning; however, the correlation of it with blood carboxyhemoglobin level (COHb) is still debated.The study aimed to evaluate the correlation between SpCO and venous COHb level and factors associated with the diagnostic accuracy of SpCO.

Material and methods

SpCO and venous COHb levels of patients with CO poisoning, according to a COHb level was 3%, were evaluated. The sensitivity, specificity, 95% CI (confidence interval), and the cut-off value of SpCO were calculated using ROC analysis at a 10% threshold for COHb. Agreement levels were calculated with Bland-Altman analysis. Risk factors affecting diagnostic accuracy were analyzed using logistic regression analysis.

Results

If the 10% threshold of COHb was accepted as the diagnostic threshold for CO poisoning, the sensitivity and specificity of SpCO were 98.4% and 100% (95% CI: 0.996-1.000) at the 6.85 cut-off point of SpCO. The scatter plot of COHb and SpCO showed a strong positive relationship at values of presentation and discharge (r = .979, p<0.001; r = .969, p<0.001). With a bias of 3.1% for the mean difference between-COHb and SpCO, the limits of agreement from Bland- Altman analysis were -0.7 to 7.1. For the 10% threshold, age and male gender have significantly increased false negativity rates (B = .074, p = 0.010, and B = 0.252, p = 0.011, respectively).

Conclusion

SpCO is a reliable method with high sensitivity and specificity; therefore, a lower cut-off points of SpCO compared to COHb level may be accepted to diagnose and follow-up CO poisoning.

Accuracy of pulse CO-oximetry to evaluate blood carboxyhemoglobin level: a systematic review and meta-analysis of diagnostic test accuracy studies

Carbon monoxide (CO) poisoning is one of the most common causes of poisoning death and its diagnosis requires an elevated carboxyhemoglobin (COHb) level. Noninvasive CO saturation by pulse oximetry (SpCO) has been available since 2005 and has the advantage of being portable and easy to use, but its accuracy in determining blood COHb level is controversial. To evaluate the accuracy of SpCO (index test) to estimate COHb (reference test). Systematic review and meta-analysis of diagnostic test accuracy (DTA) studies. Four electronic databases were searched (Medline, Embase, Cochrane Central Register of Controlled Trials, and OpenGrey) on 2 August 2022. All studies of all designs published since the 2000s evaluating the accuracy and reliability of SpCO measurement compared to blood COHb levels in human volunteers or ill patients, including children, were included. The primary outcome was to assess the diagnostic accuracy of SpCO for estimating COHb by blood sampling by modeling receiver operating characteristic (ROC) curves and calculating sensitivity and specificity (primary measures). The secondary measures were to calculate the limits of agreement (LOA) and the mean bias. This systematic review was conducted according to the Preferred Reporting Items for a Systematic Review and Meta-analysis-DTA 2018 guidelines and has been registered on International Prospective Register of Systematic Reviews (PROSPERO, CRD42020177940). The risk of bias was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Twenty-one studies were eligible for the systematic review; 11 could be included for the quantitative analysis of the primary measures and 18 for the secondary measures. No publication bias was found. The area under the summary ROC curve was equal to 86%. The mean sensitivity and specificity were 0.77, 95% confidence interval (CI, 0.66-0.85) and 0.83, 95% CI (0.74-0.89), respectively (2089 subjects and 3381 observations). The mean bias was 0.75% and the LOA was -7.08% to 8.57%, 95% CI (-8.89 to 10.38) (2794 subjects and 4646 observations). Noninvasive measurement of COHb (SpCO) using current pulse CO oximeters do not seem to be highly accurate to estimate blood COHb (moderate sensitivity and specificity, large LOA). They should probably not be used to confirm (rule-in) or exclude (rule-out) CO poisoning with certainty.

[Carbon monoxide intoxication-New aspects and current guideline-based recommendations]

Carbon monoxide poisoning is a common and potentially life-threatening intoxication, showing an interindividual variety of unspecific symptoms as well as late neurological and other sequelae. Two new German guidelines (S2k guidelines diagnosis and treatment of carbon monoxide poisoning as well as S3 guidelines oxygen therapy in the acute care of adult patients) focus on current evidence-based information on diagnostics as well as therapeutic options with considerable uncertainty remaining. This review summarizes current information and presents a flow scheme for daily practical use.

Symptoms and functional limitations related to respiratory health and carbon monoxide poisoning in Tanzania: a cross sectional study

BACKGROUND

The burden of chronic respiratory symptoms and respiratory functional limitations is underestimated in Africa. Few data are available on carbon monoxide (CO) poisoning in sub-Saharan Africa and existing data is derived from CO in ambient air, but not from biomarkers in the blood.

METHODS

Data from the Tanzanian Lung Health study, a cross-sectional study on lung health among outpatients and visitors to an urban as well as a rural hospital in Tanzania, was analyzed to describe respiratory symptoms and functional limitations. Saturation of peripheral blood with carbon monoxide (SpCO) was measured transcutaneously and non-invasively in participants using a modified pulse oxymeter indicative of CO poisoning. Univariate and multivariate analysis was performed.

RESULTS

Nine hundred and ninety-seven participants were included in the analysis, the median age of participants was 46 years (49% male). 38% of participants reported some degree of chronic shortness of breath and 26% felt limited in their daily activities or at work by this symptom. The median SpCO was 7% (IQR 4-13, range 2-31%) among all participants without active smoking status (N = 808). Participants cooking with gas or electricity had the lowest SpCO (median 5%), followed by participants cooking with charcoal (median 7%). Cooking with wood, particularly using a stove, resulted in highest SpCO (median 11.5%). Participants from households where cooking takes place in a separate room had the lowest SpCO as compared to cooking outside or cooking in a shared room inside (6% vs. 9% vs.10.5%, p < 0.01). Sex or the activity of cooking itself was not associated with a difference in SpCO. Multivariate analysis confirmed cooking in a separate room (as compared to cooking outside) and living in a rural vs. urban setting as protective factors against high SpCO.

CONCLUSION

The findings demonstrate a high burden of chronic respiratory symptoms which also cause socioeconomic impact. High levels of SpCO indicate a relevant burden of carbon monoxide poisoning in the local population. The level of CO in the blood is more dependent on shared exposure to sources of CO with the type of housing and type of cooking fuel as most relevant factors, and less on person-individual risk factors or activities.

Tips for avoiding common mistakes in out-of-hospital diagnosis of carbon monoxide poisoning

Acute carbon monoxide poisoning is the leading cause of intoxication from exogenous substances in the world. It is also a major cause of morbidity and mortality due to poisoning in the USA. In the USA, it determines to 50,000 visits per year in emergency departments with a mortality ranging from 1 to 3%. Although prevalence and incidence data reveal the large impact of carbon monoxide poisoning on public health, some studies have shown that errors in its diagnosis have a high incidence (30%) and that awareness campaigns have allowed the reduction of the same to 5%. In addition, many diagnostic and/or therapeutic errors were found both in small first aid situations and in the context of rescue units belonging to prestigious hospitals. To formulate a diagnosis, the collection of clues from the environment in which the patient is found is essential. Especially when the routine use of environmental gas detectors or handheld CO-oximeters is not possible, the emergency doctor, in addition to concentrating on the clinical presentation of the case, will have to give a quick overview of the patient and his environment. In addition to age, sex, and already known comorbidities, it is not irrelevant to evaluate socio-economic and cultural characteristics, hygiene conditions, habits, etc.The purpose of this study is to provide useful information to the doctor who comes first to the site of intoxication to reduce diagnostic and therapeutic errors in the pre- and intra-hospital phase as much as possible.

S2k guideline diagnosis and treatment of carbon monoxide poisoning

Carbon monoxide (CO) can occur in numerous situations and ambient conditions, such as fire smoke, indoor fireplaces, silos containing large quantities of wood pellets, engine exhaust fumes, and when using hookahs. Symptoms of CO poisoning are nonspecific and can range from dizziness, headache, and angina pectoris to unconsciousness and death. This guideline presents the current state of knowledge and national recommendations on the diagnosis and treatment of patients with CO poisoning. The diagnosis of CO poisoning is based on clinical symptoms and proven or probable exposure to CO. Negative carboxyhemoglobin (COHb) levels should not rule out CO poisoning if the history and symptoms are consistent with this phenomenon. Reduced oxygen-carrying capacity, impairment of the cellular respiratory chain, and immunomodulatory processes may result in myocardial and central nervous tissue damage even after a reduction in COHb. If CO poisoning is suspected, 100% oxygen breathing should be immediately initiated in the prehospital setting. Clinical symptoms do not correlate with COHb elimination from the blood; therefore, COHb monitoring alone is unsuitable for treatment management. Especially in the absence of improvement despite treatment, a reevaluation for other possible differential diagnoses ought to be performed. Evidence regarding the benefit of hyperbaric oxygen therapy (HBOT) is scant and the subject of controversy due to the heterogeneity of studies. If required, HBOT should be initiated within 6 h. All patients with CO poisoning should be informed about the risk of delayed neurological sequelae (DNS).

The diagnostic value of neurogranin in patients with carbon monoxide poisoning: Can it show early neurological damage?

BACKGROUND AND AIM

Carbon monoxide poisoning is a toxicological emergency that causes neurological complications. High serum neurogranin can be detected in acute or chronic conditions where brain tissue is damaged. This study aimed to investigate the diagnostic value of serum neurogranin level and its role in demonstrating neurological damage in patients admitted to the emergency department with carbon monoxide poisoning.

MATERIALS AND METHODS

The study was conducted prospectively on patients with carbon monoxide poisoning (patient group) and healthy volunteers (control group). Demographic characteristics and serum neurogranin level of all participants and symptoms at admission, neurological examination findings, laboratory results, and Diffusion-Weighted Magnetic Resonance Imaging results of the patient group were recorded. We used an independent sample t-test to compare neurogranin levels and bivariate correlation analysis to compare the relationship between serum neurogranin levels and data belonging to the patient group.

RESULTS

Sixty eight participants (patient group, n = 36; control group, n = 32) were included in the study. Serum neurogranin level was significantly higher in patients with carbon monoxide poisoning (0.31 ± 0.16 ng/ml) compared to control group (0.22 ± 0.10 ng/ml) (p = 0.015). The mean Glasgow Coma Scale of the patients with carbon monoxide poisoning was 14.59 ± 0.23, and of Diffusion Weighted Magnetic Resonance Imaging results were completely normal in 94.4% (n = 34). There was no correlation between serum neurogranin level and Diffusion Weighted Magnetic Resonance Imaging results (r = -0.011; p = 0.953).

CONCLUSION

Serum neurogranin level may be a new diagnostic biomarker in patients admitted to the emergency department with carbon monoxide poisoning. The high serum neurogranin levels detected in patients with normal diffusion-weighted imaging after carbon monoxide poisoning suggest that there is neurological damage in these patients, even if imaging methods cannot detect it.

An Evolving Clinical Need: Discordant Oxygenation Measurements of Intubated COVID-19 Patients

Since the first appearance of the severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) earlier this year, clinicians and researchers alike have been faced with dynamic, daily challenges of recognizing, understanding, and treating the coronavirus disease 2019 (COVID-19) due to SARS-CoV-2. Those who are moderately to severely ill with COVID-19 are likely to develop acute hypoxemic respiratory failure and require administration of supplemental oxygen. Assessing the need to initiate or titrate oxygen therapy is largely dependent on evaluating the patient’s existing blood oxygenation status, either by direct arterial blood sampling or by transcutaneous arterial oxygen saturation monitoring, also referred to as pulse oximetry. While the sampling of arterial blood for measurement of dissolved gases provides a direct measurement, it is technically challenging to obtain, is painful to the patient, and can be time and resource intensive. Pulse oximetry allows for non-invasive, real-time, continuous monitoring of the percent of hemoglobin molecules that are saturated with oxygen, and usually closely predicts the arterial oxygen content. As such, it was particularly concerning when patients with severe COVID-19 requiring endotracheal intubation and mechanical ventilation within one of our intensive care units were observed to have significant discordance between their predicted arterial oxygen content via pulse oximetry and their actual measured oxygen content. We offer these preliminary observations along with our speculative causes as a timely, urgent clinical need. In the setting of a COVID-19 intensive care unit, entering a patient room to obtain a fresh arterial blood gas sample not only takes exponentially longer to do given the time required for donning and doffing of personal protective equipment (PPE), it involves the consumption of already sparce PPE, and it increases the risk of viral exposure to the nurse, physician, or respiratory therapist entering the room to obtain the sample. As such, technology similar to pulse oximetry which can be applied to a patients finger, and then continuously monitored from outside the room is essential in preventing a particularly dangerous situation of unrealized hypoxia in this critically-ill patient population. Additionally, it would appear that conventional two-wavelength pulse oximetry may not accurately predict the arterial oxygen content of blood in these patients. This discordance of oxygenation measurements poses a critical concern in the evaluation and management of the acute hypoxemic respiratory failure seen in patients with COVID-19.

The Diagnosis and Treatment of Carbon Monoxide Poisoning

BACKGROUND

The symptoms of carbon monoxide (CO) poisoning are nonspecific, ranging from dizziness and headache to unconsciousness and death. A German national guideline on the diagnosis and treatment of this condition is lacking at present.

METHODS

This review is based on a selective literature search in the PubMed and Cochrane databases, as well as on existing guidelines from abroad and expert recommendations on diagnosis and treatment.

RESULTS

The initiation of 100% oxygen breathing as early as possible is the most important treatment for carbon monoxide poisoning. In case of CO poisoning, the reduced oxygen-carrying capacity of the blood, impairment of the cellular respiratory chain, and immune-modulating processes can lead to tissue injury in the myocardium and brain even after lowering of the carboxyhemoglobin (COHb) concentration. In patients with severe carbon monoxide poisoning, an ECG should be obtained and biomarkers for cardiac ischemia should be measured. Hyperbaric oxygen therapy (HBOT) should be critically considered and initiated within six hours in patients with neurologic deficits, unconsciousness, cardiac ischemia, pregnancy, and/or a very high COHb concentration. At present, there is no general recommendation for HBOT, in view of the heterogeneous state of the evidence from multiple trials. Therapeutic decision-making is directed toward the avoidance of sequelae such as cognitive dysfunction and cardiac complications, and the reduction of mortality. Smoke intoxication must be considered in the differential diagnosis. The state of the evidence on the diagnosis and treatment of this condition is not entirely clear. Alternative or supplementary pharmacological treatments now exist only on an experimental basis.

CONCLUSION

High-quality, prospective, randomized trials that would enable a definitive judgment of the efficacy of HBOT are currently lacking.

The detection of occult CO poisoning through noninvasive measurement of carboxyhemoglobin: A cross-sectional study

OBJECTIVES

Carbon monoxide (CO) poisoning is one of the leading causes of preventable death in the world. Our primary objective was to identify and treat individuals who are unaware of their exposure to carbon monoxide in emergency departments (EDs). Our secondary goal was to reduce the costs of diagnosis and treatment by preventing unnecessary diagnostic testing in EDs.

METHODS

In this cross-sectional study, carboxyhemoglobin (COHb) levels of patients presented with the signs of CO poisoning to the Emergency Department of Kayseri Training and Research Hospital between November 2012 and May 2013 were noninvasively measured during triage. Patients with elevated COHb levels were suspected of CO poisoning and subjected to further investigation.

RESULTS

A total of 4073 patients were enrolled in the study, and 106 (2.6%) of them were diagnosed with CO poisoning. Initial evaluation revealed headache to be the most common presenting complaint in patients with occult CO poisoning. Further evaluations to determine the accuracy of noninvasive measurements showed that noninvasive pulse CO-oxymeter and arterial blood gas (ABG) measurement were compatible.

CONCLUSIONS

The use of noninvasive pulse CO-oxymeter might reduce the morbidity and mortality associated with occult CO poisoning in patients presented with suspected CO poisoning in emergency settings.

Response time of indirectly accessed gas exchange depends on measurement method

Noninvasive techniques are routinely used for assessment of tissue effects of lung ventilation. However, comprehensive studies of the response time of the methods are scarce. The aim of this study was to compare the response time of noninvasive methods for monitoring of gas exchange to sudden changes in the composition of the inspired gas. A prospective experimental study with 16 healthy volunteers was conducted. A ventilation circuit was designed that enabled a fast change in the composition of the inspiratory gas mixture while allowing spontaneous breathing. The volunteers inhaled a hypoxic mixture, then a hypercapnic mixture, a hyperoxic mixture and finally a 0.3% CO mixture. The parameters with the fastest response to the sudden change of O2 in inhaled gas were peripheral capillary oxygen saturation (SpO2) and regional tissue oxygenation (rSO2). Transcutaneous oxygen partial pressure (tcpO2) had almost the same time of reaction, but its time of relaxation was 2-3 times longer. End-tidal carbon dioxide (EtCO2) response time to change of CO2 concentration in inhaled gas was less than half in comparison with transcutaneous carbon dioxide partial pressure (tcpCO2). All the examined parameters and devices reacted adequately to changes in gas concentration in the inspiratory gas mixture.

Altered Mental Status: Current Evidence-based Recommendations for Prehospital Care

Introduction

In the United States emergency medical services (EMS) protocols vary widely across jurisdictions. We sought to develop evidence-based recommendations for the prehospital evaluation and treatment of a patient with an acute change in mental status and to compare these recommendations against the current protocols used by the 33 EMS agencies in the State of California.

Methods

We performed a literature review of the current evidence in the prehospital treatment of a patient with altered mental status (AMS) and augmented this review with guidelines from various national and international societies to create our evidence-based recommendations. We then compared the AMS protocols of each of the 33 EMS agencies for consistency with these recommendations. The specific protocol components that we analyzed were patient assessment, point-of-care tests, supplemental oxygen, use of standardized scoring, evaluating for causes of AMS, blood glucose evaluation, toxicological treatment, and pediatric evaluation and management.

Results

Protocols across 33 EMS agencies in California varied widely. All protocols call for a blood glucose check, 21 (64%) suggest treating adults at <60mg/dL, and half allow for the use of dextrose 10%. All the protocols recommend naloxone for signs of opioid overdose, but only 13 (39%) give specific parameters. Half the agencies (52%) recommend considering other toxicological causes of AMS, often by using the mnemonic AEIOU TIPS. Eight (24%) recommend a 12-lead electrocardiogram; others simply suggest cardiac monitoring. Fourteen (42%) advise supplemental oxygen as needed; only seven (21%) give specific parameters. In terms of considering various etiologies of AMS, 25 (76%) give instructions to consider trauma, 20 (61%) to consider stroke, and 18 (55%) to consider seizure. Twenty-three (70%) of the agencies have separate pediatric AMS protocols; others include pediatric considerations within the adult protocol.

Conclusion

Protocols for patients with AMS vary widely across the State of California. The evidence-based recommendations that we present for the prehospital diagnosis and treatment of this condition may be useful for EMS medical directors tasked with creating and revising these protocols.

Carboxyhemoglobin Levels Induced by Cigarette Smoking Outdoors in Smokers

INTRODUCTION

Non-invasive screening of carboxyhemoglobin saturation (SpCO) in the emergency department to detect occult exposure is increasingly common. The SpCO threshold to consider exposure in smokers is up to 9%. The literature supporting this cutoff is inadequate, and the impact of active smoking on SpCO saturation remains unclear. The primary objective was to characterize baseline SpCO in a cohort of smokers outdoors. Secondary objectives were to explore the impact of active smoking on SpCO and to compare SpCO between smokers and non-smokers.

METHODS

This was a prospective cohort pilot study in two outdoor urban public areas in the USA, in a convenience sample of adult smokers. SpCO saturations were assessed non-invasively before, during, and 2 min after cigarette smoking with pulse CO-oximetry. Analyses included descriptive statistics, correlations, and a generalized estimating equation model.

RESULTS

Eighty-five smokers had mean baseline SpCO of 2.7% (SD 2.6) and peak of 3.1% (SD 2.9), while 15 controls had SpCO 1.3% (SD 1.3). This was a significant difference. Time since last cigarette was associated with baseline SpCO, and active smoking increased mean SpCO. There was correlation among individual smokers' SpCO levels before, during, and 2 min after smoking, indicating smokers tended to maintain their baseline SpCO level.

CONCLUSIONS

This study is the first to measure SpCO during active smoking in an uncontrolled environment. It suggests 80% of smokers have SpCO ≤ 5%, but potentially lends support for the current 9% as a threshold, depending on clinical context.

Investigation of the Relation between Carbon Monoxide Exposure/Intoxication and Tobacco-Free Narghile Products

Objectives

Use of tobacco-based narghiles may have potentially fatal consequences, such as carbon monoxide (CO) intoxication. However, there are only limited studies on the effects on human health and CO levels of tobacco-free narghile products. The primary aim of this study was to investigate the effect of tobacco-free narghile consumption on carboxyhemoglobin (COHb) levels and whether this would cause CO intoxication in active and passive narghile users.

Design

Observational study.

Methods

Four hundred ninety-nine individuals exposed to tobacco-free narghile smoke were divided into four groups; Group I: active narghile smokers, and non-cigarette smokers, Group II: active narghile smokers and active cigarette smokers, Group III: passive narghile smokers and non-cigarette smokers and Group IV: passive narghile smokers and active cigarette smokers. Fifty-nine healthy volunteers were enrolled as control groups (Group V, non-cigarette smoker controls, and Group VI, cigarette smoker controls). COHb levels were compared among the groups.

Results

Mean pre-exposure % COHb levels for groups I-IV were 2.61± 1.46, 3.00±1.37, 2.09±1.45 and 3.00±2.13, and post-exposure % COHb levels for groups were 3.45±1.92, 4.17±2.01, 2.60±1.66 and 4.50±2.32, respectively. Control groups (V-VI) % COHb levels were 0.90±0.82 and 1.60±0.85, respectively. COHb levels rose significantly after exposure to tobacco-free narghile smoke in all groups (p<0.001). COHb levels in all groups were higher than those in healthy individuals. Additionally, 12.8% of those exposed to tobacco-free narghile smoke had toxic COHb levels.

Conclusion

The use of tobacco-free narghile products represents a potential danger, and COHb levels in active and passive smokers can reach intoxication levels. (Hong Kong j.emerg.med. 2016;23:17-27)

Carbon Monoxide Exposure in Youth Ice Hockey

OBJECTIVE

To examine the effect of ice resurfacer type on carboxyhemoglobin levels in youth hockey players. We hypothesized that players in arenas with electric resurfacers would have normal, stable carboxyhemoglobin levels during games, whereas those in arenas with internal combustion engine (IC) resurfacers would have an increase in carboxyhemoglobin levels.

DESIGN

Prospective cohort study.

SETTING

Enclosed ice arenas in the northeastern United States.

PARTICIPANTS

Convenience sample of players aged 8 to 18 years old in 16 games at different arenas. Eight arenas (37 players) used an IC ice resurfacer and 8 arenas (36 players) an electric resurfacer.

INTERVENTIONS

Carboxyhemoglobin levels (SpCO) were measured using a pulse CO-oximeter before and after the game. Arena air was tested for carbon monoxide (CO) using a metered gas detector. Players completed symptom questionnaires.

MAIN OUTCOME MEASURES

The change in SpCO from pregame to postgame was compared between players at arenas with electric versus IC resurfacers.

RESULTS

Carbon monoxide was present at 6 of 8 arenas using IC resurfacers, levels ranged from 4 to 42 parts per million. Carbon monoxide was not found at arenas with electric resurfacers. Players at arenas with IC resurfacers had higher median pregame SpCO levels compared with those at electric arenas (4.3% vs 1%, P < 0.01). Players in the IC group also had a significant increase in their SpCO level during a hockey game compared with those in the electric group (2.8% vs 1%, P = 0.01). There were no significant differences in symptom scores.

CONCLUSIONS

Players at arenas operating IC resurfacers had significantly higher SpCO levels.

CLINICAL RELEVANCE

Youth hockey players in arenas with IC resurfacers have an increase in carboxyhemoglobin during games and have elevated baseline carboxyhemoglobin levels compared with players at arenas with electric resurfacers. Electric resurfacers decrease the risk of CO exposure.

Mass Casualty Triage in the Case of Carbon Monoxide Poisoning: Lessons Learned

ABSTRACTCarbon monoxide (CO) can cause mass intoxication, but no standard triage algorithm specifically addresses CO poisoning. The roles of some recent diagnostic tools in triage as well as treatment with hyperbaric oxygen are controversial. We describe a mass casualty case of CO poisoning involving 77 patients, with a focus on the triage and treatment options decided on-site. The reasons for choosing these options are reviewed, and the pitfalls that occurred and the lessons learned from this major incident are described. We discuss the potential to improve the management of such an event and strategies to accomplish this, including simplifying triage and administering oxygen to all exposed persons for 6 h. (Disaster Med Public Health Preparedness. 2018; 12: 373-378).

Anesthesia-Related Carbon Monoxide Exposure: Toxicity and Potential Therapy

Exposure to carbon monoxide (CO) during general anesthesia can result from volatile anesthetic degradation by carbon dioxide absorbents and rebreathing of endogenously produced CO. Although adherence to the Anesthesia Patient Safety Foundation guidelines reduces the risk of CO poisoning, patients may still experience subtoxic CO exposure during low-flow anesthesia. The consequences of such exposures are relatively unknown. In contrast to the widely recognized toxicity of high CO concentrations, the biologic activity of low concentration CO has recently been shown to be cytoprotective. As such, low-dose CO is being explored as a novel treatment for a variety of different diseases. Here, we review the concept of anesthesia-related CO exposure, identify the sources of production, detail the mechanisms of overt CO toxicity, highlight the cellular effects of low-dose CO, and discuss the potential therapeutic role for CO as part of routine anesthetic management.

The Accuracy of Pulse Spectroscopy for Detecting Hypoxemia and Coexisting Methemoglobin or Carboxyhemoglobin

BACKGROUND

Pulse spectroscopy is a new noninvasive technology involving hundreds of wavelengths of visible and infrared light, enabling the simultaneous quantitation of multiple types of normal and dysfunctional hemoglobin. We evaluated the accuracy of a first-generation pulse spectroscopy system (V-Spec™ Monitoring System, Senspec, Germany) in measuring oxygen saturation (SpO2) and detecting carboxyhemoglobin (COHb) or methemoglobin (MetHb), alone or simultaneously, with hypoxemia.

METHODS

Nineteen volunteers were fitted with V-Spec probes on the forehead and fingers. A radial arterial catheter was placed for blood sampling during (1) hypoxemia with arterial oxygen saturations (SaO2) of 100% to 58.5%; (2) normoxia with MetHb and COHb increased to approximately 10%; (3) 10% COHb or MetHb combined with hypoxemia with SaO2 of 100% to 80%. Standard measures of pulse-oximetry performance were calculated: bias (pulse spectroscopy measured value - arterial measured value) mean ± SD and root-mean-square error (Arms).

RESULTS

The SpO2 bias for SaO2 approximately 60% to 100% was 0.06% ± 1.30% and Arms of 1.30%. COHb bias was 0.45 ± 1.63, with an Arms of 1.69% overall, and did not degrade substantially during moderate hypoxemia. MetHb bias was 0.36 ± 0.80 overall and stayed small with hypoxemia. Arms was 0.88 and was <3% at all levels of SaO2 and MetHb. Hypoxemia was also accurately detected by pulse spectroscopy at elevated levels of COHb. At elevated MetHb levels, a substantial negative bias developed, -10.3 at MetHb >10%.

CONCLUSIONS

Pulse spectroscopy accurately detects hypoxemia, MetHb, and COHb. The technology also accurately detects these dysfunctional hemoglobins during hypoxemia. Future releases of this device may have an improved SpO2 algorithm that is more robust with methemoglobinemia.

Carbon Monoxide Exposure in Norwegian Rescue Helicopters

OBJECTIVE

Exposure to exhaust fumes from combustion engines can lead to carbon monoxide (CO) poisoning. Sea King Rescue helicopter crews are frequently subjected to engine exhaust. This study investigates the extent of CO exposure and potential for intoxication for flight crews during standard operational training procedures.

METHODS

Over a 2-week period, rescue helicopter flight crews were monitored for exposure to exhaust fumes and clinical symptoms of CO intoxication by means of a written survey and measurements of carboxyhemoglobin saturation (SpCO) with a handheld pulse CO oximeter (RAD-57; Masimo, Irvine, CA). Normal ranges for SpCO were defined as ≤ 4%.

RESULTS

Sixty-nine completed surveys and 138 SpCO measurements of 37 crewmembers were included in the study. Sixty-four percent (n = 44) experienced subjective exposure to engine exhaust during training. Clinical symptoms were reported in 8.6% (n = 6) and included exhaustion (n = 4), headache (n = 1), and nausea (n = 1). Twenty-nine percent (n = 20) showed postflight SpCO levels outside the normal range (≥ 4%). The maximum postflight SpCO level among all measurements was 7%.

CONCLUSION

Exposure to engine fumes is common, even more so during open cargo door operations. However, clinical symptoms are infrequent and mild. Toxic SpCO levels were not reached in this study, but approximately one third of postflight SpCO levels were outside the normal range.

Effect of carboxyhemoglobin on postoperative complications and pain in pediatric tonsillectomy patients

BACKGROUND

Carbon monoxide (CO) is a product of burning solid fuel in stoves and smoking. Exposure to CO may provoke postoperative complications. Furthermore, there appears to be an association between COHb concentrations and pain. We thus tested the primary hypothesis that children with high preoperative carboxyhemoglobin (COHb) concentrations have more postoperative complications and pain after tonsillectomies, and secondarily that high-COHb concentrations are associated with more pain and analgesic use.

METHODS

100 children scheduled for elective tonsillectomy were divided into low and high carbon monoxide (CO) exposure groups: COHb ≤3 or ≥4 g·dl(-1) . We considered a composite of complications during the 7 days after surgery which included bronchospasm, laryngospasm, persistent coughing, desaturation, re-intubation, hypotension, postoperative bleeding, and reoperation. Pain was evaluated with Wong-Baker Faces pain scales, and supplemental tramadol use recorded for four postoperative hours.

RESULTS

There were 36 patients in the low-exposure group COHb [1.8 ± 1.2 g·dl(-1) ], and 64 patients were in the high-exposure group [6.4 ± 2.1 g·dl(-1) ]. Indoor coal-burning stoves were reported more often by families of the high- than low-COHb children (89% vs 72%, P < 0.001). Second-hand cigarette smoke exposure was reported by 54% of the families with children with high COHb, but only by 24% of the families of children with low COHb. Composite complications were more common in patients with high COHb [47% vs 14%, P = 0.0001, OR:7.4 (95% Cl, lower = 2.5-upper = 21.7)], with most occurring in the postanesthesia care unit. Pain scores in postanesthesia care unit and one hour after surgery were statistically significantly lower in the low-exposure group [respectively, P = 0.020 (95%CI, lower = -1.21-upper = -0.80), P = 0.026 (95% CI, lower = -0.03-upper = 0.70)], and tramadol use increased at 4 h (3.5 (interquartile range: 0-8) vs 6 (5-9) mg, P = 0.012) and 24 h (3.5 (0-8) vs 6 (5-9) mg, P = 0.008).

CONCLUSION

High preoperative COHb concentrations are associated with increased postoperative complications and pain.

Prevalence of carbon monoxide poisoning in patients presenting to a large emergency department

AIMS

Carbon monoxide (CO) can cause lethal intoxication, but the burden of occult CO poisoning is still unclear. We aimed at prospectively assessing the number of patients with occult CO poisoning presenting to an emergency department within one year.

METHODS

Prospective, observational study according to the Strengthening the Reporting of Observational studies in Epidemiology (STROBE) statement for cross sectional studies at a European high volume tertiary-care emergency department.

RESULTS

Thirty-two thousand three-hundred and ninety-six consecutive patients whose vital signs were assessed at triage, regardless of their complaints. Active screening for CO-poisoning by non-invasive CO-oximetry was performed at triage. A pragmatic diagnosis of CO poisoning was made by attending physicians in 32 cases, representing 99/100,000 emergency department (ED)-patients. Three different definitions of poisoning were developed based on physicians' decision criteria, resulting in 9, 12, and 48 cases, respectively.

CONCLUSIONS

In our study population, the prevalence of CO poisoning was twice as high as previously reported. The number of cases highly depends on the definition used, with more strict definitions excluding mainly cases during the summer months, where the source of CO often remains unknown. A clear consensus on which patients have to be regarded as 'poisoned' is urgently needed in order to allow comparison across studies.

[Dermal and inhalation poisoning. Rare guests in our intensive care units?]

Patients with dermal and inhalation poisoning are uncommon in intensive care treatment. We describe the diagnostics and specific toxicological treatment of patients with hydrofluoric acid burns. For inhalation poisoning, we focus on smoke inhalation, especially the management of cyanide and carbon monoxide poisoning. Special attention is given to the use of hyperbaric oxygenation for the treatment of carbon monoxide poisoning.

Unrecognized carbon monoxide poisoning leads to a multiple-casualty incident

BACKGROUND

Carbon monoxide (CO) is regarded as a leading cause of morbidity and mortality. It endangers not only patients, but also health care professionals, especially emergency medical services (EMS) personnel because CO exposure is often unknown at the time EMS is called.

OBJECTIVE

Our objective was to report a case of unrecognized CO exposure during the treatment of a patient that finally led to the hospitalization of 11 EMS personnel.

CASE REPORT

A 71-year-old man was found unconscious in the basement of his house. EMS was called and, due to ST-segment elevations on electrocardiogram, the patient was treated for acute coronary syndrome. Unknown to EMS personnel, ongoing CO exposure was the cause of the patient's symptoms. EMS staff finally had to be evacuated by firefighters, and a total of 12 persons, including the initial patient, had to be hospitalized.

CONCLUSIONS

In the prehospital setting, hazardous environments always have to be considered as potential causes of a patient's altered status. Together with the correct use of modern equipment, such as permanently switched-on CO detectors, this can help avoid harm to both patients and staff.

Accuracy of carboxyhemoglobin detection by pulse CO-oximetry during hypoxemia

BACKGROUND

Carbon monoxide poisoning is a significant problem in most countries, and a reliable method of quick diagnosis would greatly improve patient care. Until the recent introduction of a multiwavelength "pulse CO-oximeter" (Masimo Rainbow SET(®) Radical-7), obtaining carboxyhemoglobin (COHb) levels in blood required blood sampling and laboratory analysis. In this study, we sought to determine whether hypoxemia, which can accompany carbon monoxide poisoning, interferes with the accurate detection of COHb.

METHODS

Twelve healthy, nonsmoking, adult volunteers were fitted with 2 standard pulse-oximeter finger probes and 2 Rainbow probes for COHb detection. A radial arterial catheter was placed for blood sampling during 3 interventions: (1) increasing hypoxemia in incremental steps with arterial oxygen saturations (SaO2) of 100% to 80%; (2) normoxia with incremental increases in %COHb to 12%; and (3) elevated COHb combined with hypoxemia with SaO2 of 100% to 80%. Pulse-oximeter (SpCO) readings were compared with simultaneous arterial blood values at the various increments of hypoxemia and carboxyhemoglobinemia (≈25 samples per subject). Pulse CO-oximeter performance was analyzed by calculating the mean bias (SpCO - %COHb), standard deviation of the bias (precision), and the root-mean-square error (A(rms)).

RESULTS

The Radical-7 accurately detected hypoxemia with both normal and elevated levels of COHb (bias mean ± SD: 0.44% ± 1.69% at %COHb <4%, and -0.29% ± 1.64% at %COHb ≥4%, P < 0.0001, and A(rms) 1.74% vs 1.67%). COHb was accurately detected during normoxia and moderate hypoxia (bias mean ± SD: -0.98 ± 2.6 at SaO2 ≥95%, and -0.7 ± 4.0 at SaO2 <95%, P = 0.60, and A(rms) 2.8% vs 4.0%), but when SaO2 decreased below approximately 85%, the pulse CO-oximeter always gave low signal quality errors and did not report SpCO values.

CONCLUSIONS

In healthy volunteers, the Radical-7 pulse CO-oximeter accurately detects hypoxemia with both low and elevated COHb levels, and accurately detects COHb, but only reads SpCO when SaO2 is more than approximately 85%.

Practice recommendations in the diagnosis, management, and prevention of carbon monoxide poisoning

Carbon monoxide (CO) poisoning is common in modern society, resulting in significant morbidity and mortality in the United States annually. Over the past two decades, sufficient information has been published about carbon monoxide poisoning in the medical literature to draw firm conclusions about many aspects of the pathophysiology, diagnosis, and clinical management of the syndrome, along with evidence-based recommendations for optimal clinical practice. This article provides clinical practice guidance to the pulmonary and critical care community regarding the diagnosis, management, and prevention of acute CO poisoning. The article represents the consensus opinion of four recognized content experts in the field. Supporting data were drawn from the published, peer-reviewed literature on CO poisoning, placing emphasis on selecting studies that most closely mirror clinical practice.

Noninvasive pulse CO-oximetry expedites evaluation and management of patients with carbon monoxide poisoning

PURPOSES

Pulse CO-oximetry (Rad-57; Masimo Corp, Irvine, CA) has been available since 2005. To date, all published clinical studies have focused on clinical reliability and whether the device enhances case finding through screening of various populations. This study examines whether use of pulse CO-oximetry shortens the time to diagnosis and treatment of patients with carbon monoxide (CO) poisoning.

BASIC PROCEDURES

Data from the joint Undersea and Hyperbaric Medical Society/Centers for Disease Control and Prevention CO poisoning surveillance system from August 2008 to July 2011 were analyzed. Of 1711 cases of CO poisoning treated with hyperbaric oxygen in the United States and reported through the system, 1606 had their initial carboxyhemoglobin (COHb) level measured by laboratory CO-oximetry and 105 by pulse CO-oximetry. Patients were selected from the laboratory CO-oximetry group to match each of the 105 patients evaluated by pulse CO-oximetry in 5 characteristics--age, sex, race/ethnicity, intent of poisoning, and occurrence of loss of consciousness. Measures of timeliness in measurement and management were compared between the 2 groups.

MAIN FINDINGS

Patients with initial COHb measurement by pulse CO-oximetry had significantly shorter time to measurement of COHb, higher average levels of COHb, and shorter time from the end of CO exposure to the initiation of hyperbaric oxygen treatment. On average, patients evaluated by pulse CO-oximetry reached the hyperbaric chamber 1 hour faster than did patients evaluated by laboratory CO-oximetry (P < .01).

PRINCIPLE CONCLUSIONS

Pulse CO-oximetry is associated with more rapid diagnosis and initiation of hyperbaric oxygen therapy in CO-poisoned patients compared with laboratory CO-oximetry. The impact on clinical outcome remains to be determined.

The measurement of carboxyhemoglobin and methemoglobin using a non-invasive pulse CO-oximeter

The pulse CO-oximeter (Rad-57 Masimo Corporation, Irvine, CA) allows non-invasive and instantaneous measurement of carboxyhemoglobin (COHb) and methemoglobin (MetHb) percentage level using a finger probe. However, the accuracy and reliability of the Rad-57 against the gold standard of venous or arterial blood samples have not been clearly established. Thus, the objective of this trial is to evaluate the accuracy and precision of the Rad-57 pulse CO-oximeter by comparing it with venous sampling on the same subjects. Nine healthy subjects were subjected to carbon monoxide such that it raised the COHb to 10-14% on two different days and pooled together. The COHb and MetHb were measured with a blood gas-analyzer and simultaneously with the Rad-57 as the COHb increased from 1.4 to 14%. Results were compared using linear regression and a Bland and Altman method comparison. Mean bias and precision for COHb measured with the Rad-57 was -1% and 2.5%, respectively. The mean bias and precision for MetHb measured with the Rad-57 was 0.0% and 0.3%, respectively. The ability to detect a COHb ≥ 10% occurred in 54% of the samples in which COHb was ≥ 10-14%. In conclusion, the Rad-57 provides a reading that is between -6% and +4% of the true COHb value for 95% of all samples. The Rad-57 seems to be a good substitute as a first screening test of COHb when the pulse CO-oximeter reads <15%.

The current status of continuous noninvasive measurement of total, carboxy, and methemoglobin concentration

Intraoperative early detection of anemia, identifying toxic levels of carboxyhemoglobin after carbon monoxide exposure and titrating drug dosage to prevent toxic levels of methemoglobin are important goals. The pulse oximeter works by illuminating light into the tissue and sensing the amount of light absorbed. The same methodology is used by laboratory hemoglobinometers to measure hemoglobin concentration. Because both devices work in the same way, efforts were made to modify the pulse oximeter to also measure hemoglobin concentration. Currently there are 2 commercial pulse oximeters (Masimo Rainbow SET and OrSense NBM-200MP) that measure total hemoglobin concentration and one (Masimo) that also measures methemoglobin and carboxyhemoglobin. In this review, we describe the peer-reviewed literature addressing the accuracy of these monitors.