Proper sensor placement will ensure fast, accurate readings. Illustration Masimo Corp.
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After successfully rescuing two trapped Fire Department of New York (FDNY) firefighters, an officer complained of lightheadedness and mild shortness of breath. Initial assessment revealed him to be normotensive, slightly tachycardic and tachypneic with a pulse oximetery reading of 100%. Paramedics using a CO-oximeter device determined his carboxyhemoblobin (COHb) level was 22%—a dangerously high level; subsequently, he received ALS care and was transported to a hospital facility.
This is an example of why firefighters need to be screened for elevated COHb levels at emergency scenes. It supports the argument that CO assessment should be considered a standard of care, especially at potential CO exposure incidents.
Screening in the Field
Studies have shown that the emergency department (ED) misses the diagnosis 30–50% of the time.(1–3) If you extrapolate that percentage to the unpredictable prehospital environment, you will realize the potential exposure to missed cases and service liability that CO exposures present.
In 2008, the FDNY began using CO-oximeter monitoring in the field to determine COHb levels on symptomatic patients at the scene of emergencies where CO toxicity was suspected, as well as on asymptomatic occupants when elevated CO levels were detected by atmospheric gas CO monitors. In January 2009, this was expanded to evaluate all personnel at the scene of third-alarm or greater fires as part of our rehabilitation program and to evaluate long-term cardiovascular affects of elevated COHb levels.
The region also began to implement a smoke-inhalation protocol that included the treatment for patients with suspected cyanide poisoning, along with monitoring for CO exposure. An initiative was also undertaken to develop a protocol to transport patients with signs and symptoms of CO intoxication or elevated levels of COHb directly to 9-1-1 receiving hospitals that have the ability to provide emergent hyperbaric oxygen (HBO) therapy on a 24/7 basis.
This protocol will further enhance our system’s ability to rapidly identify, properly treat and ensure an appropriate continuum of care for these patients. Table 1 illustrates this transport decision.
CO as a Vital Sign?
The FDNY evaluated and adopted the use of CO-oximetery for two specific operational considerations.
The first was the ease of use and reliability of a CO-oximetery instrument. Of the 3,300 calls handled daily, many are for fire and non-fire emergencies likely to expose patients to CO. We were interested in accurately assessing these patients so that proper treatment and transport could be rendered.
Furthermore, our system was challenged at scenes with a high number of occupants being evacuated and/or rescued from homes where high levels of CO were detected, which made them likely victims of CO poisoning. It was felt that the ability to reliably assess and triage this population and prevent them from becoming unnecessary patients would preserve valuable EMS and hospital resources.
The second consideration was the use of CO-oximetery as an assessment tool during firefighter rehab at large-scale assignments. Three-alarm or greater fires occur 50–60 times a year in the FDNY system. These fires often have more than 150 firefighters and EMS providers operating for extended periods.
A mandatory evaluation for COHb was introduced as part of the rehab for all personnel at these assignments. Over the past 18 months, several firefighters were found to be CO toxic and asymptomatic, which allowed EMS to treat and transport them early and appropriately. This initiative was important, largely due to published research linking repeated CO toxicity to early development of cardiovascular disease.
CO as a Standard of Care
The ability to measure COHb has been a welcome addition to prehospital monitoring capabilities, but further research is required. Some in the medical community have been hesitant to initiate prehospital CO monitoring because COHb levels don’t correlate well with symptoms.(4)
Although studies have shown the accuracy of noninvasive CO-oximetry when compared to laboratory COHb measurements, a recent study suggests a discrepancy between the two, resulting in false positive and false negative readings.(5) This underscores the importance of using proper methods to obtain accurate SpCO readings and shielding the sensor from excessive light.
Further validation studies are needed before we can suggest that non-invasive CO-oximetery measurements join the extended required vital signs list. Still, we’ve experienced the distinct ability to rapidly assess and determine that CO toxicity is present, often in asymptomatic people. Therefore, the addition of portable CO-oximetry has become an important assessment tool in our medical and rehab operations toolkits.
Disclosure: The authors have reported their EMS system has received support from Masimo in the form of clinical trial RAD-57 CO-oximeters for evaluation and research purposes.
References
1. Baker MD, Henretig, FM, Ludwig S. Carboxyhemoglobin levels in children with non-specific flu-like symptoms. J Pediatr. 1988;113:501–504.
2. Barret L, Danel V, Faure J. Carbon Monoxide poisoning. A diagnosis frequently overlooked. J Toxicol Clin Toxicol. 1985;23:309–313.
3. Grace TW, Platt FW. Subacute carbon monoxide poisoning. Another great imitator. JAMA. 1981;246:1698–700.
4. Hampson NB, Hauff NM. Carboxyhemoglobin levels in carbon monoxide poisoning: Do they correlate with the clinical picture? Am J Emerg Med. 2008;26:665–669.
5. Suner S, McMurdy J. Masimo Rad-57 pulse CO-oximeter for noninvasive carboxyhemoglobin measurement. Expert Review of Medical Devices. 2009;6:125–130.
6. Touger M, Birnbaum A, Wang J, et al. Performance of the RAD-57 Pulse CO-Oximeter Compared with Standard Laboratory Carboxyhemoglobin Measurement. Ann Emerg Med. 2010 Jun 2. [Epub ahead of print].
This article originally appeared in an editorial supplement to the October 2010 JEMS as “A Standard of Care: Early results from FDNY point to the benefits of regular CO monitoring in patients & firefighters.”
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