Carbon Monoxide Poisoning
2014 Case Definition

Background

Carbon monoxide (CO) is a colorless, odorless, nonirritating gas that is produced through the incomplete combustion of hydrocarbons. Sources of CO include combustion devices (e.g., boilers and furnaces), motor-vehicle exhaust, generators and other gasoline or diesel-powered engines, gas space heaters, woodstoves, gas stoves, fireplaces, tobacco smoke, and various occupational exposures. CO poisoning is a leading cause of unintentional poisoning deaths in the United States. Unintentional, non-fire related CO poisoning is responsible for approximately 450 deaths and 21,000 emergency department (ED) visits each year.^{1, 2}

Clinical Criteria

• A person with signs or symptoms consistent with a diagnosis of carbon monoxide poisoning. There is no unique list of CO poisoning symptoms: the condition presents with a non-specific profile³. Typical symptoms include, but are not limited to, headache, dizziness, fatigue/weakness, nausea/vomiting, confusion, shortness of breath, chest pain, and loss of consciousness.
• A person whose poison control center report indicates an exposure to carbon monoxide (Call type= exposure, Substance = carbon monoxide) with minor, moderate, or major health effects (Medical outcome = minor, moderate, major, death).

Laboratory Criteria For Diagnosis

A person with a carboxyhemoglobin (COHb) level of ≥ 5.0% as measured by a blood sample or pulse CO-oximetry.

Criteria to Distinguish a New Case from an Existing Case

A case should be categorized as a new (incident) case when there is either:

• New exposure to CO from different exposure source.
• Repeated exposure as defined by having the same exposure source as previous occurrence where the criteria used to designate a case has been resolved prior to repeat exposure.

A case is categorized as a prevalent case when there are multiple reports for the same episode, such as when there are multiple COHb lab test results or when a patient receives multiple hyperbaric treatments following a single poisoning event.

Suspected

Reporting Systems: Clinicians, Medical Examiners/Coroners, Laboratories, Hyperbaric Chambers, Poison Centers:

• • (S1) A carboxyhemoglobin (COHb) level, as measured by a pulse co-oximeter, of equal to or greater than 9% and less than or equal to 10%.

-OR-

• • (S2) In the absence of laboratory confirmation of an elevated COHb, a report of a patient with non-specific symptoms (headache, dizziness, and/or fatigue/weakness) AND environmental monitoring consistent with an exposure to CO.

-OR-

• • (S3) A report of a patient with an environmental exposure consistent with CO poisoning.⁴

-OR-

• (S4) In the absence of laboratory confirmation of an elevated COHb, a report of a patient with non-specific symptoms (headache, dizziness, and/or fatigue/weakness) AND exposure to a source of CO.

Administrative Data (in the absence of case investigation):

• • (S5) ICD-9-CM Coded Data: In the absence of an N-986 code: (1) a medical care record in which an E-code that mentions CO exposure as a cause of illness is listed anywhere in the record (E818.0-.9, E825.0-.9, E844.0-.9, E867, E868.0, E868.1, E890.2, E891.2), or (2) a medical care record in which an E-Code where carbon monoxide exposure is plausible is listed (N987, E838.0-.9, E869.9, E951.0, E951.1, E951.8, E952.9, E958.1, E962.2, E962.9, E968.0, E972, E978, E979.3, E981.0, E981.1, E981.8, E988.1). [Note: ICD codes are listed in Appendix 1 of the Position Statement].

-OR-

• • (S6) ICD-10 Coded Data: In the absence of T58 code, a mortality record in which a code that mentions CO exposure as a cause of illness, is listed anywhere in the record (X47, X67, Y17).

-OR-

• • (S7) Poison Control Center (PCC) Data: A record of a case with "exposure" recorded as the type of call, when the exposure substance was carbon monoxide, AND a minor medical outcome was reported.

-OR-

• (S8) Worker’s Compensation (WC) Data: A record of a workers compensation submitted claim where CO poisoning is listed.

Probable

Reporting Systems: Clinicians, Medical Examiners/Coroners, Laboratories, Hyperbaric Chambers, Poison Centers:

• • (P1) A carboxyhemoglobin level, as measured by a blood sample, that is 9% ≤ COHb ≤ 10% in smokers or for those whom smoking status is unknown.

-OR-

• • (P2) A carboxyhemoglobin level, as measured by a pulse co-oximeter of > 10%.

-OR-

• • (P3) Loss of consciousness or death without alternative explanation AND exposure to a source of CO.

-OR-

• • (P4) In the absence of environmental monitoring, a report of a patient with signs or symptoms consistent with acute CO poisoning AND concurrent environmental exposure as that of a confirmed CO poisoning case.

-OR-

• (P5) A PCC report (status= closed) with “exposure” recorded as the type of call, when the exposure substance was carbon monoxide, AND a moderate or major medical outcome or death was reported.

Administrative Data (in the absence of case investigation):

• • (P6) ICD-9-CM Coded Data: A medical care record in which an E-code indicating acute carbon monoxide poisoning inferred from motor vehicle exhaust gas exposure is listed anywhere in the record, i.e., E868.2, E952.0, or E982.0. [Note: ICD codes are listed in Appendix 1 of the Position Statement].

-OR-

• • (P7) Poison Control Center (PCC) Data: A record of a case (status= closed) with "exposure" recorded as the type of call, when the exposure substance was carbon monoxide, AND a moderate or major medical outcome or death was reported.

-OR-

• (P8) Workers’ Compensation (WC) Data: A record of a workers compensation paid claim where CO poisoning is listed.

Confirmed

Reporting Systems: Clinicians, Medical Examiners/Coroners, Laboratories, Hyperbaric Chambers, Poison Centers:

• • (C1) A carboxyhemoglobin level, as measured by a blood sample, of > 5% in nonsmokers⁵.

-OR-

• • (C2) A carboxyhemoglobin level, as measured by a blood sample of > 10% in smokers or for whom smoking status is unknown.⁵

-OR-

• • (C3) In the absence of laboratory confirmation of an elevated COHb level, signs or symptoms consistent with acute carbon monoxide poisoning AND a positive environmental exposure consistent with CO poisoning.⁴

-OR-

• (C4) A PCC report (status = closed) with "exposure" recorded as the type of call, when the exposure substance was carbon monoxide, AND a minor, moderate or major medical effect or death was reported AND a positive environmental exposure consistent with CO poisoning was indicated in the case notes⁴.

Administrative Data (in the absence of case investigation):

• • (C5) ICD-9-CM Coded Data: (1) A medical care record for CO poisoning in which the Nature of Injury code N-986 "Toxic effect of CO" is listed anywhere in the record, OR; (2) a medical care record in which an External Cause of Injury code (E-code), indicating exposure to carbon monoxide (exclusively) is listed anywhere in the record, i.e., E868.3, E868.8, E868.9, E952.1, or E982.1. [Note: ICD codes are listed in Appendix 1 of Position Statement].

-OR-

• • (C6) ICD-10 Coded Data: A mortality record in which T58, Toxic Effect of Carbon Monoxide, is listed anywhere in the record.

-OR-

• (C7) ICD-10-CM coded data: A medical care record for CO poisoning in which T58, Toxic Effect of Carbon Monoxide, is listed anywhere in the record.

• Carbon Monoxide Poisoning | 2019 Case Definition