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Home>Topics>>EMS: Using Pulse Oximetry

EMS: Using Pulse Oximetry

Tue, 10 Apr 2012|

FIre Engineering EMS Editor Mike McEvoy discusses using pulse oximetry, a method of determining the oxygen level in your patient. Mike also discusses some tips and issues with readings on pulse oximetry devices.



[MUSIC] Hi. Welcome to Training Minutes. Today we're gonna talk about using pulse oximetry which has been added to the first responder and EMT curriculum. Pulse oximetry is a method of determining the oxygen level in your patient. Has many limitations. First thing that we're gonna do is place the probe on the patient. So we have a finger probe that we're using with this device and we're gonna chose a finger that has the best blood flow. Of the fingers on your hand your ring finger tends to be the finger that has the highest blood flow so we'll place the probe on a patients ring finger we could put it on any one of the other fingers preferentially one of the three middle fingers not the thumb not the pinky and then we'll. Watch the pulse oximeter as it boots up. It's going to collect a pulse ox reading which you see is 100% here, and the heart rate from the patient. Now some of the issues with pulse oximetry have to do with. Things that it may detect other than oxygen that's in the patient. It's looking at the hemoglobin and determining the saturation of the hemoglobin with oxygen. It could be fooled, as firefighters know, by carbon monoxide. It's unable in convention pulse oxymeters. Like this device to be able to tell the difference between oxyhemoglobin and carboxyhemoglobin. So, if this person was pulled from a fire and had a 20% carboxyhemoglobin the pulse ox would still read 100%, not recognizing. That 20% of that was carbon monoxide. So that's the first caveat about using pulse oximetry. Clearly, if a patient's pulled from a fire and has a pulse oximeter using a conventional pulse oximeter that can't tell the difference between oxyhemoglobin and carboxyhemoglobin, then. The saturation was low, we would say well there's a problem with that patient. The other question that people often ask is cyanide, if a patient was poisoned with cyanide, would the pulse oximeter have an effect from the cyanide, and the answer to that seems to be not. Pulse oximeters do not seem to be affected in their readings by cyanide levels in the blood stream. Next question is what's the strength of the blood flow to the digit where you placed the probe. Now we chose what we believed to be the best blood flow by using the ring finger on this patient. If for some reason we weren't getting a good signal, if he had low profusion, we may need to place the probe on another digit on his hand, or perhaps on a toe. Now our probes are specially made to put on the ear, there are probes that are made to go on the nose and there are probes that are made to go on the forehead. You need to use a probe that's designed for whatever application you're using, in this case a finger probe on a finger. On this particular oximeter, which is made by Masimo, as well as oximeters that are made by Datex Ohmeda. And by Philips, we have an indicator of the actual profusion on the patient that's called profusion index. If you're using a brand of Auximiter that has profusion index, in an adult patient, 1.4 is the cutoff for reliable versus an unreliable signal. In this instance. His profusion index is well over 4 and so his profusion to the extremity that we have the probe on is excellent. If you're doing it on a neonate 1.27 is the threshold for good versus bad profusion. The other question is nail polish. Can nail polish interfere with pulse oximetry? And, in fact, three colors of nail polish actually do throw the pulse oximetry signal off: black, blue and green nail polish. So if your patient is wearing nail polish you may use a nail polish remover, a prep pad similar to an alcohol pad that's designed to remove nail polish. Has acetone on it. And the acetone would be used to wipe the nail polish off the patient's nail. You could also position the probe so that it reads sideways through the finger avoiding the nail bed completely. Reading sideways would eliminate the effect black, blue or green nail polish that the patient had. Another question is, what about ambient light? And there are certain forms of ambient light that could interfere with the pulse [INAUDIBLE] signal. Sunlight is one, and very bright sunlight may require you to put a towel over the extremity that you have the pulse [INAUDIBLE] probe on. Lights that indoors such as flourescent which you may have in the back of your ambulance or your rescue. Or xenon light that may be in a sports stadium or in a place where that sort of lighting is uses could interfere with the pulse ox signal and again putting a towel over the extremity will eliminate that interference from the readings. That are being taken. Some people question whether sickle cell crisis, or sickle cell anemia affects pulsox readings. The answer to that is no. Sickle cell does not affect a pulsox reading. The other question is, what about darkly pigmented skin patients? So people who are, for example, African American or Indian, who have a darker pigmentation to their skin. Pulsox is not affected by darkly pigmented patients. And finally, hyperbilirubinemia, patients who, for some reason, have an elevated level of bilirubin in their bloodstream, perhaps they're in liver failure, or perhaps they have some other condition that's causing excessive levels of bilirubin, most patients typically have a yellow appearance to their skin. That does not interfere with pulse aux. So we talked in another fire engineering video series about using pulse oximmetry to take blood pressure, and again if you were trying to assess a blood pressure, you could place the probe on the extremity, pump your blood pressure cuff up on the same extremity, and watch for the pulsation. As you let the air out of the blood pressure cuff and get a rough idea of a systolic blood pressure. So, those are some tips for using pulse oximetry. A common tool, something that's been added to our curriculum in the new first responder and EMT curriculum. And it very helpful device to determine what the oxygen nation status of your patient is and as oxygen become more important and we start to realize some of the detriments of giving oxygen to patients who have dramatic conditions such as trauma acute myocardial infarction or stroke. Where excessive levels of oxygen may actually hurt the injury to those patients and make their conditions worse pulse oximetry is a valuable tool for assessing of patients and the EMS field. Thanks for watching Training Minutes. I'm Mike McEvoy, the EMS editor Fire Engineering.

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