Protocols for Avoiding Carbon Monoxide Misdiagnosis

Carbon monoxide misdiagnosis must be addressed with emergency protocols developed that focus on environmental and epidemiological factors.

By Rebecca Martin

We have noted in previous blogs that it is widely agreed that educating first responders and emergency room staff to the protocols of assessing incoming patients for carbon monoxide poisoning is one of the priorities in improving outcomes in emergencies.

Avoiding carbon monoxide misdiagnosis requires investigation and communication from the scene to the emergency room. EMS need to investigate how many people are ill, the onset of that illness and whether pets are also impacted.

In larger area-wide emergencies, such as the ice storms in Texas, we saw medical facilities gearing up to meet demands even before officials had acted. Even though facilities were unable to assess and treat patients in the most optimum manner, they were able to spread the warnings through the media quickly.  They were also able to provide triage to treat those most in need through emergency measures, even though oxygen was in short supply.

The same call to action for response teams came about as a result of boat-related incidents which were often historically mistaken for anything from drunkenness to drownings, but later proven to be due to carbon monoxide poisoning.

Pre-Education Key in Natural Disasters

We now see numerous warnings, prior to events like hurricanes, in Florida newspapers advising residents of the potential dangers of generators during disasters. And while I have previously addressed those specific factors in the general population who may be in need of additional efforts in education, we need to look at another facet of the problem; misdiagnosis during rescue, assessment and treatment.

It is generally believed that in cases of non-acute exposure the majority of cases are carbon monoxide misdiagnosis is rampant. (By non-acute, we mean where people have had non-deadly exposures, spread over multiple events.) A survey by UK-based charity, Carbon Monoxide Support, showed that only one case out of 77 was correctly identified. (Carbon Monoxide Support. The effects of chronic exposure to CO. Leeds: Carbon Monoxide Support; 1997.) This survey could easily be applied to acute poisonings as well as we have seen evidence that this is true in many boating accidents where cause of death was not correctly attributed to carbon monoxide exposure. This can greatly increase the carnage from carbon monoxide as patients presenting at the emergency room with all the classic symptoms might be returned to environments which have the potential to cause even further harm, even death.

An article by Thomas H. Greiner, PhD. From the Department of Agricultural and Biosystems Engineering of Iowa State University, published in 1997, states that:

“It can be easily misdiagnosed by medical personnel as highlighted by a 1995 incident in Cleveland. Ohio. Five persons went to the local hospital with flu-like symptoms. Surviving relatives report the doctor was asked three times if it was carbon monoxide poisoning and that he said no, it was the flu. The family was sent home and three days later all five died from carbon monoxide poisoning. A Kentucky study found 23.6% of persons presenting to a hospital during February 1985 had elevated carboxyhemoglobin concentrations. None were initially diagnosed as suffering from carbon monoxide poisoning.” See

Many of these earlier studies have laid the groundwork for reassessing the protocols for patients who present with symptoms of carbon monoxide poisoning which may mimic the symptoms of other common conditions such as the flu or food poisoning.

Environmental Clues to  Avoid Carbon Monoxide Misdiagnosis

One of the components of the current preferred protocols is questioning how many people in a particular environment have become symptomatic. EMS (Emergency Medical Services) and first responders are the key to determining whether carbon monoxide is present. Better information is imperative, not only for the safety of those they are responding to, but also for the safety of EMS or other first responders  arriving on the scene. If the right inquires are not made at the scene, it is much harder to get the diagnosis right later.

A call may begin with an activated carbon monoxide alarm. It is important to emphasize that no activated alarm should be ignored. The alarm goes off if there is carbon monoxide in the air at levels that are expected to poison anyone. Carbon monoxide is odorless and it is urgent to get to fresh air immediately. There is a substantial difference between the “chirping” of a dead battery and an alarm. According to, four beeps and a pause means carbon monoxide has been detected. A regular continuous beep means it’s time to replace batteries. Five beeps means your detector should be replaced.

EMS may also be warned if they an alarm has sounded. This knowledge can be lifesaving, which is another reason to always use appropriate and correctly placed carbon monoxide detectors.

In some instances a concerned family member or neighbor may place the call, and in other instances, someone inside the residence or area may have placed a call. In these instances EMS needs to be able to assess the situation upon their arrival and call for appropriate assistance in carrying out a rescue or retrieval.

Classic Indicators Alone will Result in Carbon Monoxide Misdiagnosis

Classic teaching about for emergency personnel is to look for “cherry skin”, a deep red flushed skin color caused by high levels of carboxyhemoglobin in the blood. However, this condition is usually only present in near death or fatal cases. According to the,

“The signs and symptoms of carbon monoxide poisoning are variable and non-specific.”… “The more common CO poisoning symptoms are hard to differentiate from the flu, gastroenteritis and other viral illnesses.”

Multiple People Impacted an Important Clue

EMS must look for clues from the surrounding scene which take into account the time of year, the surroundings (including ventilation. “Were the windows closed?”), the number of people similarly impacted at the scene, and the presence or absence of carbon monoxide detectors. Presence of fuel burning devices are also taken into account, such as the presence of a generator, a home being heated by a gas stove or gas burning furnaces and water heaters.

In almost every case we have seen where 911 was alerted without an alarm going off, it was that multiple people got sick at or near the same time. The pattern is often, one person is ill or passes out. This is not attributed to an environmental cause. When the second, then the third person has the same symptoms, then the possibility of CO is considered.

Sick Pets May Indicate CO Poisoning

EMS should never ignore the clue that pets have been acting strange or have been sick. Dogs are particularly good at smelling the underburned hydrocarbons that come with incomplete combustion. While CO is odorless, these hydrocarbons are not. Humans may not notice this smell until carbon monoxide gets to highly lethal levels. Also, pets as they are smaller and my respirate faster, may get ill or die before humans notice the symptoms.

Once rescue has been achieved and patients are relocated into the fresh air, oxygen treatment can begin even before transport to the emergency room.

The Challenge of Brain Damage Misdiagnosis

Why is it so hard to identify carbon monoxide symptoms immediately by medical means only? Because they resemble so many other illnesses and require differential diagnosis in the emergency room to verify. Symptoms can resemble the flu. However, unlike the flu, carbon monoxide poisoning is never accompanied by a fever. It can also present as chest pains or heart palpitations. Or confusion, agitation, weakness, drowsiness; the list of symptoms is long and diverse.

An EMS crew well-versed in looking for potential carbon monoxide poisonings can provide important information to the emergency room staff. If EMS identify CO as a risk,  valuable time is saved and oxygen treatment can begin immediately. This is invaluable in that immediate treatment with oxygen is the most effective. Testing for carboxyhemoglobin in the blood can also be done immediately to confirm the diagnosis of carbon monoxide poisoning. This is a preferred scenario for an incoming patient who has entered emergency care with a documented suspicion of carbon monoxide poisoning along with details of the environmental factors they are coming from.

In other cases the emergency room staff are left with the task of diagnosis and must determine the environmental circumstances through a thorough interview, if possible. They will need to ask about possible sources of carbon monoxide, signs and symptoms, cognitive issues, loss of consciousness, as well as other medical information.

But what if you have made it to the emergency room and are given a diagnosis of flu or migraine? 84% of patients seeking treatment for carbon monoxide poisoning present with headaches. You, as a patient can request to be tested for carbon monoxide exposure or that your family member is tested. However, a normal test finding may not indicate that carbon monoxide poisoning has not occurred. Levels in the blood may decrease and not correlate to the severity of the poisoning that has occurred or the potential outcome of the damages by the time the blood is tested. This is particularly true with children, especially smaller children. Carboxyhemoglobin levels in a child can can drop much faster than in an adult. Further, oxygen therapy may have begun prior to testing the blood as well.  In the event a test shows normal levels, there are many other diagnostic tools that can be used to confirm a diagnosis of carbon monoxide poisoning.

News stories often relate the incidence of several people being transported to the hospital, assessed or treated, and then sent home. It seems to be a happy ending. Even if the home or establishment has been cleared as safe to return to, there are still hidden dangers. These dangers occur because of the delayed damage carbon monoxide poisoning can cause. Often patients are released with directions for follow up with a family physician where they become their own record of their subsequent problems in that the patient is sometimes the least aware of any changes which may be occurring. Those closest to the patient may notice changes before the patient does.

The neurological deterioration may not appear until days, weeks, after the incident. Click here for more on delayed symptoms of carbon monoxide poisoning. As we have shared in previous blogs, many of the signs that such deterioration is occurring is evident in the changed behavior of the person. Problems are most likely to become evident on a return to school or work, or in social interactions. When untreated and unaddressed these physical changes can lead to mental changes such as depression as things spiral out of control. The patient released from the emergency room after an initial diagnosis and oxygen treatment is not going to receive the same ongoing care that a person that is hospitalized would receive.

In this way, carbon monoxide poisoning is very similar to any type of traumatic brain injury, what we used to call hidden injuries. However, modern medical science is daily uncovering new visible proof that brain injury is no longer invisible. The mechanics of inflammation inherent in carbon monoxide are pointing to deficits which we are, even now, just beginning to document fully. And these deficits have clear causes. The damage from the delayed sequelae of carbon monoxide poisoning can have a profound impact on victims which is often only detected in testing if the victim is fortunate enough to have a physician concerned enough to make a referral. Damage to the basal ganglia can have far reaching neurological sequelae which researchers are discovering can affect us on every level. Much of the time delayed sequelae are undiagnosed which can lead to a poor recovery and further problems.

The answer to misdiagnosis has always existed in establishing protocols for treatment, developed by experts, to address misdiagnosis and under-diagnosis. Protocols guide EMS services as to what their response should be on the scene of a potential incident. Protocol guides the emergency room staff in their differential diagnosis and treatment. And protocols can guide physicians in their expected approach to follow up patients. And more recently, more requests to establish protocols for emergency responders  have been addressed to keep them from danger during rescue or retrieval.

In the case of protocols for follow up physicians, just as EMS teams provide first-hand information at the scene which later helps in the emergency room–so too family members provide invaluable knowledge as to the problems a victim may experience days or weeks after a carbon monoxide poisoning. If the victim seems different it is worth bringing this to the attention of the physician as well. The patient may think they are fine, or wish they were fine, or even be in denial that there is something wrong. But their behavior is not fine at all.

Advances have been made in establishing response other carbon monoxide protocols, as we have seen in boating carbon monoxide incidents. Concerted efforts were made to educate EMS responders to consider carbon monoxide poisoning after many deaths initially ruled as drownings were found to be the result of carbon monoxide exposure. When you consider that one person on a boat may have appeared to drown, this protocol helps EMS responders to look at all passengers on the boat and take appropriate actions. Where carbon monoxide detectors are one side of the carbon monoxide equation, medical protocols are the other side of the equation. And unfortunately, universal protocols have usually only come about following a tragedy and most often the result of family advocacy or litigation.

Perhaps what is questionable is why has it taken us so long to establish universal protocols to avoid carbon monoxide misdiagnosis? Evacuations, injuries, and deaths due to carbon monoxide are mainstream events and not rare events by any means. But just as we meet resistance to universal carbon monoxide detector legislation, many of the protocols for medical intervention are still in need of re-evaluation. Because of this, patients go undiagnosed. And those undiagnosed fall through the cracks.

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