That one oxygen finger probe thingy
Oximeters have gotten quite cheap these days, some units retail for just a couple hundred dollars. There's no doubt to the contribution they've made in medicine. But, in the wrong hands they can (and do) become a missused medical gadget.
An oximeter reading is such a small part of the clinical picture, a good clinician won't hang their hat on one. Oximeters are used in the hospital or cardiac clinic during exercise stress testing, along with EKG and blood pressure monitoring. As the patient follows a precise exercise protocol all these parameters (along with patient symptoms) help suggest whether a cardiopulmonary disease exists.
Being cheap, oximeters are also used (almost anywhere) during exercise tolerance testing. In this context, if the person exercising starts looking like hell, and the oximeter reads 80%, then you start thinking about following up with additional medical testing and intervention. Otherwise, on a normal, healthy individual, readings have no real value outside the awe of gadgetry.
Here's my quick list of things that can effect oximeter readings:
Movement. The nicer models show an LCD wave form of the "pulse." A reading with an erratic waveform may not be accurate. If the patient grips that bar on the treadmill too tight, or can't hold the probe finger still during exercise, it's tuff to get a good reading.
Poor circulation at the place the probe is. Cold fingers, peripheral vascular disease, etc. can effect the reading.
Nail polish, rough skin, pigmented skin, oil, sweat or moisture on the skin or probe. The light the probe directs into the finger can get altered by these barriers. I think most the latest models are not effected by skin pigmentation.
Anemia. The measurement represents saturation in the blood plasma, most oxygen is carried in the blood via red blood cells. Someone with too few red blood cells may be hypoxemic (not enough oxygen in the blood) but have perfectly normal oximeter readings.
Carbon Monoxide. Readings are even effected by cigarettes. The oximeter reads CO like oxygen, offering a falsely high reading. (Too few EMT's know this at a fire.)
Apnea. Oximeters readings on little premature babies respond quickly when respirations stop. But you and me can go several minutes without a breath before that number drops. In teaching, I've only had one or two students able to get an oximeter to go below 90% by holding their breath. (They see spots first.)
An oximeter reading is such a small part of the clinical picture, a good clinician won't hang their hat on one. Oximeters are used in the hospital or cardiac clinic during exercise stress testing, along with EKG and blood pressure monitoring. As the patient follows a precise exercise protocol all these parameters (along with patient symptoms) help suggest whether a cardiopulmonary disease exists.
Being cheap, oximeters are also used (almost anywhere) during exercise tolerance testing. In this context, if the person exercising starts looking like hell, and the oximeter reads 80%, then you start thinking about following up with additional medical testing and intervention. Otherwise, on a normal, healthy individual, readings have no real value outside the awe of gadgetry.
Here's my quick list of things that can effect oximeter readings:
Movement. The nicer models show an LCD wave form of the "pulse." A reading with an erratic waveform may not be accurate. If the patient grips that bar on the treadmill too tight, or can't hold the probe finger still during exercise, it's tuff to get a good reading.
Poor circulation at the place the probe is. Cold fingers, peripheral vascular disease, etc. can effect the reading.
Nail polish, rough skin, pigmented skin, oil, sweat or moisture on the skin or probe. The light the probe directs into the finger can get altered by these barriers. I think most the latest models are not effected by skin pigmentation.
Anemia. The measurement represents saturation in the blood plasma, most oxygen is carried in the blood via red blood cells. Someone with too few red blood cells may be hypoxemic (not enough oxygen in the blood) but have perfectly normal oximeter readings.
Carbon Monoxide. Readings are even effected by cigarettes. The oximeter reads CO like oxygen, offering a falsely high reading. (Too few EMT's know this at a fire.)
Apnea. Oximeters readings on little premature babies respond quickly when respirations stop. But you and me can go several minutes without a breath before that number drops. In teaching, I've only had one or two students able to get an oximeter to go below 90% by holding their breath. (They see spots first.)
posted by nawledge at
9:31 PM
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