Carbon Monoxide Poisoning
2019 Case Definition

Background

Carbon monoxide (CO) is a colorless, odorless, nonirritating gas that is produced through the incomplete combustion of carbon-containing substances. Sources of CO include: boilers: furnaces, cars and trucks, generators and other gasoline or diesel-powered engines, gas and propane heaters, woodstoves, gas stoves, fireplaces, tobacco smoke, forklifts, and fires. The most common location of exposures causing CO poisoning are in homes and less commonly in workplaces. CO poisoning occurs from breathing in elevated air levels of carbon monoxide. Unusual sources include exposure to methylene chloride, which is metabolized to CO and hemolysis, with increased metabolism of hemoglobin. Symptoms are generally non-specific and commonly include headache, dizziness, weakness, vomiting, chest pain and confusion. Large exposures can result in loss of consciousness, arrhythmias, seizures, or death. Unintentional, non-fire related CO poisoning is responsible for approximately 450 deaths and 21,000 emergency department (ED) visits each year.^1,2,3 CO poisoning is a leading cause of unintentional poisoning deaths in the United States.² Outbreaks of CO poisoning associated with equipment used during natural disasters have been well documented.^4-8

For surveillance purposes, Tier 1 reporting refers to the process of healthcare providers or institutions (e.g., clinicians, clinical laboratories, hospitals, poison control centers) submitting basic information to governmental public health agencies about cases of carbon monoxide poisoning that meet certain reporting requirements or criteria. Cases of carbon monoxide poisoning may also be ascertained by the secondary analysis of administrative data or through syndromic surveillance algorithms where individual information is available for follow-up case investigation. Tier 2 surveillance for carbon monoxide poisoning is based upon secondary analysis of administrative data without access to personal identifiers.

Clinical Criteria

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

Presumptive clinical evidence:

• Loss of consciousness OR
• Death

Supportive clinical evidence:

• A person with signs or symptoms consistent with carbon monoxide poisoning, which may include elevated pulse Carbon Monoxide (CO)-oximetry measurement and/or non-specific symptoms such as nausea, vomiting, confusion, shortness of breath, and chest pain.

Laboratory Criteria For Diagnosis

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

Confirmatory laboratory evidence:
A person who does not smoke, or a child (age < 14 years) whose smoking status is unknown, and has a carboxyhemoglobin (COHb) level of ≥ 5.0% as measured in a blood sample ^9-11

OR

A person who smokes, or a person (age ≥ 14 years) whose smoking status is unknown, with a carboxyhemoglobin (COHb) level of > 12.0% as measured in a blood sample^10-11

Presumptive laboratory evidence:
A person who smokes, or whose smoking status is unknown (age ≥ 14 years), and has a carboxyhemoglobin (COHb) level of ≥ 9.0% and ≤ 12.0% as measured in a blood sample

Supportive laboratory evidence:
A person who does not smoke, or a child (age < 14 years) whose smoking status is unknown, and has a carboxyhemoglobin (COHb) level of ≥ 2.5% and < 5.0% as measured in a blood sample¹²

OR

A person who smokes, or whose smoking status is unknown (age ≥ 14 years), and has a carboxyhemoglobin (COHb) level of ≥ 7.0% and < 9.0% as measured in a blood sample¹¹

Epidemiologic Linkage

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

A person who was present and exposed in the same CO exposure event as that of a confirmed CO poisoning case.

Criteria to Distinguish a New Case from an Existing Case

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

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

• • New exposure to CO from different exposure source

OR

• 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 person 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.

Exposure

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

Confirmatory exposure evidence*:
A person who had an exposure to an elevated level of CO based on a dedicated or multi-gas meter/instrument (e.g., fire department notation) for a known duration that is consistent with CO poisoning.

Possible exposure evidence*:

• A person who was in a location where a CO detector's alarm sounded,
  OR
• A person who had onset of CO-related symptoms associated physically and temporally with a CO-emitting source (e.g., gasoline-powered generator, power washer, malfunctioning furnace, and fire)

*Note: Exposure evidence that is provided by the patient is sufficient for meeting exposure evidence criteria.

Suspected

• A person with supportive laboratory evidence OR
• A person with supportive clinical criteria AND possible exposure evidence

Probable

• A person with presumptive laboratory evidence* OR
• A person with presumptive clinical evidence AND possible exposure evidence, OR
• A person with presumptive or supportive clinical evidence AND epidemiologic linkage

*Other plausible clinical explanations should be considered, including chronic obstructive lung disease and hemolysis.

Confirmed

• A person with confirmatory laboratory evidence* OR
• A person with presumptive or supportive clinical evidence AND with confirmatory exposure evidence

* Other plausible clinical explanations should be considered, including chronic obstructive lung disease and hemolysis.

Tier 2 (Using secondary analysis of administrative data without access to personal identifiers):

Suspected:

Poison Control Center Records:
A person whose poison control center record indicates an exposure to carbon monoxide AND a minor medical outcome (see Appendix 3 )

Workers compensation records:
A person whose workers compensation submitted claim contains a finding, problem, diagnosis, or other indication of exposure to carbon monoxide or carbon monoxide poisoning (see Appendix 4 ).

Healthcare records, including hospital discharge and emergency department records:

• A person whose healthcare record contains a diagnosis that is inclusive of carbon monoxide poisoning by sources other than motor vehicle exhaust (see Appendix 2).
• A person whose emergency department record mentions exposure to carbon monoxide in the chief complaint.

Death Certificates:
A person whose death certificate lists a cause of death that is inclusive of carbon monoxide poisoning, toxic effect of carbon monoxide, or carbon monoxide exposure as a cause of death or a significant condition contributing to death (see Appendix 5) .

Probable:

Healthcare records, including hospital discharge and emergency department records:
A person whose healthcare record contains a diagnosis of carbon monoxide poisoning by motor vehicle exhaust (see Appendix 2 )

Poison Control Center Records:
A person whose poison control center record indicates an exposure to carbon monoxide AND a moderate medical outcome, major medical outcome, or death (see Appendix 3 )

Workers compensation records:
A person whose workers compensation paid claim contains a finding, problem, diagnosis, or other indication of exposure to carbon monoxide or carbon monoxide poisoning (see Appendix 4 ).

Confirmed:

Healthcare records, including hospital discharge and emergency department records:
A person whose healthcare record contains an explicit diagnosis of carbon monoxide poisoning (see Appendix 2 )

Death Certificates:
A person whose death certificate explicitly lists carbon monoxide poisoning, toxic effect of carbon monoxide, or carbon monoxide exposure as a cause of death or a significant condition contributing to death (see Appendix 5 ).

Case Classification Comments

The Case Classification section above refers to Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation).

• Carbon Monoxide Poisoning | 2014 Case Definition