A pulse oximeter is a device
that clips onto your finger and reads your heart
rate as well as the percent of oxygen in your
blood. It was developed as a way to detect
hypoxia (a condition caused by insufficient
oxygen). The hemoglobin in your blood
bonds to oxygen and carries it through your
circulatory system to your body's cells. A
pulse oximeter works by emitting an infrared
light that shines through the body's tissue to a photosensor on
the other side. The infrared light is able to
detect the amount of hemoglobin that is
saturated with (or carrying) oxygen. The pulse
oximeter will display a number that indicates
the percent of hemoglobin that is saturated with
oxygen. A pulse oximeter reading (denoted by
SpO2) in the high 90s (i.e. 96%-99%) is
considered normal.
- Clip the pulse oximeter on. The pulse oximeter must be clipped onto a part of the body where light can shine through the blood flowing through the arteries. This includes a finger (where the pulse oximeter is most commonly placed on adults), toe, earlobe or across the bridge of the nose. Insert the finger into the same end of the pulse oximeter as the little white power button. Switch it on by pressing the button (it may switch on automatically when you put it on the finger).
- Ensure the pulse
oximeter is giving you an accurate reading.
There are some scenarios that will result in
the pulse oximeter providing either an
inaccurate reading or no reading at all. A
good way to determine whether the pulse
oximeter is providing an accurate reading is
to compare the pulse rate on the pulse
oximeter to the pulse rate you get by
taking the patient's pulse manually. If
they do not correspond, the likelihood is
that you are not getting an accurate reading
form the pulse oximeter. Some common
scenarios that result in an erroneous
reading include:
- Nail polish - if the pulse oximeter is clipped on a finger.
- Excessive movement by the patient
- Hypothermia or a cold injury to the extremities
- Anaemia (not enough iron in the blood)
- Carbon monoxide poisoning
- Certain types of seizures
- Shock (hypo perfusion) associated with blood loss or poor perfusion
- Remain still. As noted above, excessive movement can result in the pulse oximeter providing you with an inaccurate reading. Your casualty should try to remain relatively still while the pulse oximeter is taking its reading.
- Assess the results.
A normal reading, for a person breathing
room air, is in the high 90s. A reading of
anywhere from 96% SpO2 through 99% SpO2 is
typical. A reading of
95% SpO2 or less could indicate hypoxia and
should be investigated. An SpO2 reading of
90% or less indicates significant hypoxia
and requires immediate action.
The pulse oximeter will also record the heart rate. Normal heart rates are as follows, depicted in beats per minute (bpm):
