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Pulse Oximeter Readings Chart
Finger Pulse Oximeter Readings Chart
A pulse oximeter continuously measures the level of oxygen saturation of
haemoglobin in the arterial blood. It can detect hypoxia much sooner than the
anaesthesia provider can see clinical signs of hypoxia such as cyanosis. This ability
to provide an early warning has made the pulse oximeter essential for safe
The oximeter probe consists of two parts, the light emitting diodes (LEDs) and a light detector (called
a photo-detector). Beams of light are shone through the tissues from one side of the probe to the
other. The blood and tissues absorb some of the light emitted by the probe. The light absorbed by
the blood varies with the oxygen saturation of haemoglobin. The photo-detector detects the light
transmitted as the blood pulses through the tissues and the microprocessor calculates a value for the
oxygen saturation (SpO2).
PRACTICAL USE OF THE PULSE OXIMETER
• Turn the pulse oximeter on: it will go through internal calibration and checks.
• Select the appropriate probe with particular attention to correct sizing and where it will go (usually
finger, toe or ear). If used on a finger or toe, make sure the area is clean. Remove any nail
• Connect the probe to the pulse oximeter.
• Position the probe carefully; make sure it fits easily without being too loose or too tight.
• If possible, avoid the arm being used for blood pressure monitoring as cuff inflation will interrupt
the pulse oximeter signal.
• Allow several seconds for the pulse oximeter to detect the pulse and calculate the oxygen
• Look for the displayed pulse indicator that shows that the machine has detected a pulse. Without
a pulse signal, any readings are meaningless.
• Once the unit has detected a good pulse, the oxygen saturation and pulse rate will be displayed.
• Like all machines, oximeters may occasionally give a false reading – if in doubt, rely on your
clinical judgement, rather than the machine.
• The function of the oximeter probe can be checked by placing it on your own finger.
• Adjust the volume of the audible pulse beep to a comfortable level for your theatre – never use on
• Always make sure the alarms are on.
Role of pulse oximetry during Covid-19 pandemic
• Covid-19 is a new condition and we are still learning the best ways of assessing its severity in the
• Evidence-based guidelines, that are useful to us in our usual practice, are not currently available.
• We know that pulse oximetry can be a useful aid to clinical decision making but it is not a
substitute for a clinical assessment, nor sufficient for diagnosis by itself.
• Pulse oximetry is valuable in triaging potentially hypoxic patients in the home or GP
surgeries/assessment centres, to help determine which patients require further assessment or
• Anecdotally we are being told by clinicians that they are detecting people with symptoms of Covid19 infection but not experiencing shortness of breath, who then on performing pulse oximetry are
found to be hypoxic.
If the SpO2 reading of a long-term care facility resident with COVID-19 is below baseline, refer the
person for further evaluation and possible treatment. Other people should contact a health care provider for shortness of breath or when SpO2 is less than 95%.
A person’s oxygen levels may be low if they feel short of breath, are breathing faster than usual, or feel
too sick to do their usual daily activities, even if a pulse oximeter says their oxygen levels are normal.
People should call a doctor or another health care provider right away if they have these symptoms.