IT’S 0500 HOURS, AND YOU AND YOUR EMS PARTNER are anxiously waiting for the end of the shift. You monitor your scanner and hear the fire department being dispatched to a two-story private dwelling in your response area for a carbon monoxide (CO) emergency run. As you wonder out loud if your unit will get dispatched, several thoughts race through your head: Will we get the job as a standby for a “fire” call? Will we be dispatched to support the hazardous materials unit? Or, most likely, you will think that maybe this is just another nuisance alarm where “I will stand by and watch others work until someone presents with signs or symptoms.” Worse yet, from your experience, you think, “I won’t even get the call.”
So, whose call is this anyway? Is a CO emergency a fire/hazmat call when only EMS is needed after confirmation of the presence of symptomatic patients? Is a CO emergency an EMS call that may necessitate fire/hazmat support to supplement an initial EMS response? Or, is it an emergency run that routinely requires fire and EMS response, working together, to successfully mitigate the incident and ensure that no health and safety hazard exists?
This article offers the perspective that a CO call is an EMS call until proven otherwise instead of a fire/hazmat call where EMS is not summoned unless there are potential victims. Whether treating patients who have been evacuated from a fire in an enclosed space or responding to a CO alarm activation, it is essential that you have a keen understanding of CO, its effects on the body, and the wide range of signs and symptoms that depend on a variety of variables to ensure that you don’t miss people exposed to CO.
According to the Centers for Disease Control and Prevention (CDC), hundreds of people suffer debilitating injury [from CO], there are more than 500 accidental deaths per year attributable to unintentional CO exposure, and more than 2,000 deaths per year are ruled as suicide by intentional CO poisoning.1
WHAT IS CO?
CO is a common by-product of incomplete combustion; it is present whenever fossil fuels are burned. It is a colorless, odorless, tasteless, nonirritating gas. Because you can’t see, taste, smell, or sense CO, it can kill you before you even know it is present in your environment. Fire/EMS responders should remember that CO is also a compressed gas found in general industry (labeled UN 1016) and a cryogenic liquid (labeled UN 9202). Therefore, CO poisoning can occur in certain industrial settings even in the absence of appliances that rely on burning fuels for power.2
CO’s physical properties are listed in Table 1. It is not expected that responders commit the physical findings of all possible chemicals to memory, but it is important that you have a general understanding of CO and its behavior.3
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The flammability range, expressed as the range between the upper explosive limit (UEL) and the lower explosive limit (LEL), is rather wide; therefore, you should act to control ignition sources. The immediately dangerous to life or health value is expressed in parts per million (ppm). This number may seem a bit on the high side, but EMS providers should be cautious, because they typically do not respond with self-contained breathing apparatus (SCBA) and atmospheric levels in an enclosed environment can climb quickly. Of particular note is that the vapor density is just about equal to that of the ambient air. Instead of rising to the highest point (lighter than air) or sinking to the low-lying areas, CO acts like the ambient air and travels through the entire occupancy, following natural air flow. This translates into poisonous gases presenting themselves across the occupancy instead of lingering near the offending source. Never rule out exposure because the occupants report they were not near fuel-fired appliances.
Potential Sources of CO
There are many potential sources of CO production in the typical home. They include blocked or clogged chimney openings, portable heaters/space heaters, gas clothes dryers, a wood-burning fireplace/stove, gas stoves and ovens, gas heaters (forced air/hot water, a corroded or disconnected water heater), vent pipes, a leaking chimney pipe or flue, auto exhaust in the garage, yard equipment exhaust in a garage or shed, and the use of gas grills in enclosed spaces.
As every firefighter knows, CO is present at fire scenes; it lingers long after the fire has been extinguished, and the synergistic effects of CO and hydrogen cyanide gas are real threats to firefighters and occupants entrapped in fire in an enclosed space.
High-Risk Individuals
Although everyone is at risk from the adverse health effects or death from CO exposure, some individuals are more vulnerable than others. These high-risk individuals include unborn babies, infants and children, the elderly, individuals with a history of heart or lung disease, and individuals under the influence of alcohol or drugs. The signs and symptoms vary in individuals and are influenced by three main factors: the concentration of CO in the environment; the duration of exposure; and the workload and breathing rate during the period of exposure. As is typical with many other chemical exposures, the dose/body weight/rate relationship is directly proportional to the onset and acuity of signs and symptoms.4
CDC case classifications for CO exposures are as follows:
- Suspected case-a potentially exposed patient is being evaluated for exposure, but no specific credible exposure threat exists.
- Probable case-a clinically compatible case with a high index of suspicion following a credible exposure threat.
- Confirmed case-clinically compatible cases with laboratory tests and biologic samples confirming exposure.
EMS providers should consider using these classifications when providing prearrival reports and on written patient care documents.5
Exposure Hazards
As we recall from our routine hazardous materials training, a chemical can enter and harm the body in five ways: inhalation, absorption, ingestion, injection, and through the eyes. As a gas, CO represents a significant inhalation hazard and is classified as a systemic asphyxiant; therefore, its effects on the body present in an asphyxiant toxidrome. Systemic asphyxiants are chemicals that interfere with the body’s ability to perform aerobic (with oxygen) metabolism-in this case, by affecting cytochrome oxidase and interfering with the oxygen-delivery mechanism by displacing oxygen from the red blood cell (RBC). Hemoglobin is the portion of the RBC that carries oxygen. CO is attracted to the hemoglobin at a much greater ratio (240:1) than oxygen, meaning that, when given a choice, CO will preferentially bind to hemoglobin, easily displacing oxygen. The resultant poisonous compound is carboxyhemoglobin (COHb). As a result, the body systems reliant on oxygen are the first to manifest key signs of dysfunction (Table 2).
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Exposures can be acute (a sudden unexpected exposure to moderate to high levels in a short exposure period) or chronic (repeated and prolonged exposures to lower levels over a prolonged exposure period). EMS providers will readily identify acute exposures, but they must seek out the chronically exposed patient with a solid scene assessment, a thorough understanding of-and faith in-the atmospheric monitoring techniques employed at the scene. They also must be able to recognize a wide variety of signs and symptoms while taking the medical history and performing a physical exam.
Signs and Symptoms
Signs and symptoms that may present at low to moderate levels include headache/impaired judgment; dizziness/confusion/loss of memory/altered mental status; weakness/fatigue/sleepiness; visual disturbances; vertigo/tinnitus; nausea, vomiting; chest tightness; and dyspnea.
At higher levels, signs and symptoms can include rapid progression through any one or more of the above and lead to loss of consciousness, seizure, coma, and death.
Conventional wisdom and experience tell EMS providers not to rely on people to present as patients, because they may not know they are at risk and may perceive general malaise as ordinary everyday feelings. Additionally, confusion and weakness inhibit the thought process, which in turn influences perceived danger and ability to escape a dangerous environment.
Also, do not rely on poor skin color as an indicator of hypoxia secondary to a CO exposure. First, cyanosis is usually absent because carboxyhemoglobin is bright red in color. Even though our training curricula references “cherry red skin,” this is typically only a postmortem finding. According to one British study, only one out of 100 live patients with CO poisoning exhibited cherry red skin coloring.6 Patients who have been unconscious on a hard surface may present with skin erythemia (redness) and bullae (blisters) at dependent areas.
Since the human body is so dependent on taking in oxygen and eliminating carbon dioxide (CO2) and other waste products to maintain an acid-base balance in the very tight range of 7.35 to 7.45, the smallest lack of oxygen uptake at the cellular level affects several body systems.
EMS ON-SCENE
It is of paramount importance that EMS providers be part of every CO emergency response. Say that in the opening scenario above, your ambulance is dispatched to stand by at the CO detector call in a two-story private dwelling. Would you sit idly by at the ready in a reactive stance, waiting for the fire department personnel to bring you occupants presenting with a chief complaint of some sort, or would you take a more proactive approach and engage in your own response objectives under a unified incident command system established for the incident? While firefighters take atmospheric readings and survey for potential offending sources, you, as an EMS provider, should concurrently be performing a scene assessment. First, conduct an initial scene survey on arrival to ensure that the scene is safe. Once the scene is deemed safe and there is no need for SCBA and specialized protective clothing, remove the patient from the environment, away from the offending source as soon as possible. In most cases, decontamination of the skin is not necessary, although flushing the eyes may be of some benefit.
Suffice it to say that if patients present in obvious distress or with obvious signs or symptoms, it’s a no-brainer. You go to work and follow your treatment and transport protocols. You don’t want to miss the more subtle exposures. As part of your scene assessment, proactively seek out people to make sure they are not patients. While interviewing occupants, look for signs or symptoms of exposure. Follow the customary hazardous materials approach for patient assessment.
Start by engaging the occupants in conversation. Ask if any members of the home are feeling ill or if anyone has a headache; feels sleepy, dizzy, or confused; or feels nauseous. Now that you have addressed the common symptoms, move on to the more subtle ones: Does anybody have difficulty recalling the events of the past 24 hours? Is there ringing in the ears? Is there difficulty speaking or swallowing? Do family members feel better when away from the house?
You should have a basic understanding of the significance of the atmospheric monitoring results for occupants. For example, you should be able to equate the exposure values with common symptoms and know that the time of onset to symptoms and the severity of those symptoms are inversely proportional to the number of ppm and the corresponding percentage of substance in the air, as seen in Table 3. Of course, individuals will respond differently, based on a host of variables and underlying physical conditions. Atmospheric monitoring values are expressed in ppm. This translates into the percentage of substance in the atmosphere. For example, a reading of 200 ppm means that there is .02 percent substance in the air, 400 ppm equals .04 percent, 800 ppm equals .08 percent, and so on. The higher the ppm, the higher the percentage of substance in the atmosphere, and the greater the hazard to unsuspecting occupants.
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The National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) have set the allowable permissible exposure limits (PEL) at 35 to 50 ppm (eight-hour workday/40-hour workweek). Normal, well-adjusted appliances put out between 5 and 15 ppm; that number climbs to more than 30 ppm for poorly adjusted appliances. Noticeable signs and symptoms appear at 70 ppm; serious signs and symptoms appear at 150 to 200 ppm.
To successfully resolve the emergency response, the unified command post should issue an occupant advisory based on atmospheric monitoring results and interviews with and physical examinations of occupants. In my jurisdiction, for example, we use the occupant advisories identified in Table 4. Colleagues always follow local protocols.
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Patient Assessment
As in every other patient assessment, pay particular attention to the ABCs (airway, breathing, circulation). These guidelines are drawn from standard practice and generally accepted curricula; always follow local protocols and medical direction.
- Airway. Ensure an open airway; suction as needed. If the patient is a victim of fire, anticipate upper airway obstruction caused by swelling from exposure to superheated gases. If oropharyngeal burns, as evidenced by soot around the nose or mouth, and dysphonia, aphonia, or stridor are present, provide positive-pressure ventilation with a bag-valve-mask (BVM) and 100-percent oxygen, or perform endotracheal intubation (ETI), if qualified. Remember, if ventilations with the BVM are successful and transport times are short, you risk causing laryngospasm by attempting ETI.
- Breathing. Provide high-flow oxygen through a nonrebreather face mask at 12 to 15 liters per minute. Assess for noncardiogenic pulmonary edema. Reminder: The use of pulse oximetry is not recommended for patients exposed or potentially exposed to CO. False positives will result, because the infrared sensors in the typical pulse oximeter cannot differentiate between oxygen and CO attached to the RBC. More recent advances in technology have resulted in noninvasive cooximetry monitors, which are capable of assessing for oxygen and CO and have been proven effective in differentiating between oxygen and CO molecules on the RBC, thereby offering more advantageous application.
- Circulation. Monitor the pulse for rate and quality, and note the skin color, condition, and temperature. Apply cardiac monitor, if available, and treat dysrhythmia per local protocol. Establish an IV to keep the vein open, if qualified.
History of Present Illness, Focused Physical Exam
Obtain a complete set of vital signs, a history of present illness, and a past medical history including medications and allergies and transport to the appropriate emergency department for further evaluation. Indicators for hyperbaric oxygen therapy (HBOT) typically include COHb via laboratory analysis of >25 percent, lactic acidosis, abnormal psychometric testing, seizure, coma, or acute myocardial infarction. Follow local protocol for transport decisions.
RESPONDER SAFETY
In many jurisdictions, EMS providers respond to emergencies to provide emergency incident rehabilitation support functions. The physical and mental demands associated with firefighting and other emergency operations in hazardous situations, coupled with environmental dangers of extreme heat and humidity or extreme cold, create conditions that may adversely impact the safety and health of emergency response personnel. Additionally, in specific types of response activities, emergency responders may be exposed to CO as a by-product of incomplete combustion, which places them at increased risk for occult exposure.
Adequate rest and rehydration activities and routine medical monitoring of emergency response personnel have become commonplace in the out-of-hospital setting. The Federal Emergency Management Agency (FEMA) and the United States Fire Administration (USFA) have issued Emergency Incident Rehabilitation standard operating procedures (SOPs) that designate a Rehabilitation sector (Rehab) within the EMS operations of the Logistics component of the incident command system (ICS). They are useful in providing guidance to EMS providers, including clinical parameters for the decision-making process. Screening for exposure to CO should be commonplace in rehab sector activities.
Responding to CO emergencies can be challenging. In many cases, people with vague or mild symptoms tend to downplay their symptoms by attributing them to other common causes. As public safety responders, however, it is our responsibility to ensure that people have a clear understanding of the risks they face from occult exposure to CO as well as to ensure that atmospheric levels are within normal range. Remember that in many instances, occupancies are well ventilated and offending appliances are likely turned off because of the excellent advice of the emergency dispatchers.
In cases such as these, the likelihood of finding elevated CO levels in the atmosphere diminishes. Because of that probability, EMS response to CO emergencies should be concurrent with a fire department response in all cases so that a complete scene assessment can take place and the screening for health effects associated with CO exposure are weighted evenly with atmospheric monitoring results in satisfactorily mitigating the situation.
References
1. “CO Poisoning,” At Risk Populations Fact Sheet, www.cdc.gov.
2. “Chemical Sampling Information Fact Sheet,” U.S. Department of Labor.
3. Pocket Guide to Hazardous Chemicals, National Institute for Occupational Safety and Health (NIOSH).
4. CO Poisoning, www.wikipedia.org.
5. “Preventing CO Poisoning after Exposure,” www.CDC.gov.
6. Journal of Emergency Medicine, Elsevier Sciences, Inc.; 2002 (22:2), 213-214.
ROBERT DELAGI is the chief of prehospital medical operations and program agency director for the Suffolk County (NY) Department of Health Service’s Division of Emergency Medical Services and a 30-year veteran of the fire/EMS service. He is a nationally registered paramedic and has a master’s degree in health policy management. Delagi is a member of the Suffolk County Terrorism Response Task Force, sits on several local and state disaster preparedness work groups, and is an adjunct assistant professor at the Suffolk County Community College and SUNY Empire State College.
