What is Anemia?
- blood cells have reduced capacity to carry oxygen
when measuring SpO2 - that is % of saturation, not amt of cells carrying blood (ie you only have 20 cells that are fully saturated w o2, = high SpO2, but you really need 200; the reading doesnt capture that)
SpO2 - oxygenated vs. deoxygenated hemoglobin, Anemia - overall absorption signature that correlates with hemoglobin concentration
Here are some situations when the SpO2 monitoring via your smartwatch can fall short. source
In order to judge a patient’s condition, ideally, you would like to have blood oxygen saturation expressed as a percentage of the total hemoglobin that is saturated with oxygen.
Under many circumstances, that is the reading you get from pulse oximeters. However, if the patient has a large amount of non- functional hemoglobin, the reading is not accurate.
Several situations can lead to such large amounts of non-functioning hemoglobin. Carbon monoxide poisoning and even heavy smoking increase the amount of carboxyhemoglobin, non-functioning hemoglobin.
So if you are a heavy smoker, chances are that your SpO2 readings obtained via any of these leading smartwatches may not be correct.
The same holds for users who suffer from Anemia. Damage to red blood cells may cause anemia, a lack of red blood cells, and thus hemoglobin in the blood.
An anemic patient may not have enough functioning hemoglobin in the blood to oxygenate the tissues.
The small amount of functioning hemoglobin in the blood may be well saturated with oxygen, so the patient may have a normal SpO2 reading, but the patient may not have enough oxygen going to the tissues.
The human body reduces the heat lost by the skin by constricting the peripheral blood vessels. So if you are performing an on-demand SpO2 reading in colder temperatures, you will have to account for the inaccuracy in the readings.
Hypoxemia is low oxygen levels in your blood and
Hypoxia:
Hypoxemia: