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In this next video, we are going to look at pulse oximetry. Pulse oximetry gives us an indication of the oxygen levels of the patient. Essentially, it measures the amount of oxygen that is combined with haemoglobin circulating around the body. Whilst the pulse oximetry gives us a good indication of the oxygenation state of the patient, it's not without its problems. We apply the sensor to a patient's finger. Yet if that patient's cold or if they have Raynaud's syndrome or something that affects circulation to the distal part of the body, then we may not get an accurate reading. Likewise, we may get a false reading from a patient who has been affected by carbon monoxide poisoning. The machine cannot establish a difference between oxygen and carbon monoxide.

Pulse oximetry has come in various shapes and sizes and essentially they all have a screen which displays the reading and a sensor which we apply in this case to a patient's finger. When we first put the sensor on it may take about 15 seconds for the reading to come up and I would say that in this time that if you know that you are dealing with a hypoxic patient, do not wait for the reading to come up to confirm that the patient actually is hypoxic, begin oxygen therapy. We can always titrate the oxygen dose at a later time, depending on the pulse oximetry reading. In patients with long-term COPD, their oxygen saturation may well be in the 88 to the 92% zone, and this is fine. But if a patient's without COPD, we will be looking to get a SPO2 reading of above 95%.

The pulse oximetry probe works by shining a red light through the finger and picks up the amount of oxyhemoglobin passing through the light. Now, on a case where a patient may have nail varnish, we may not be able to get an accurate reading and it's possible to actually apply the sensor rather than anterior, posterior but to do it from side to side, like so. There are also alternative probes that we can use to attach to ears, noses and this can also go on a toe as well and which will give us a good indication of the distal circulations thereof that patient.