What should my oxygen saturation level be?
A range of 94-99% is normal for healthy adults breathing room air which contains 21% oxygen. Anyone who is not achieving the critical blood oxygen saturation level of 90% (SpO2) or of 55-60mmHg (SaO2), may require additional oxygen. A qualified medical practitioner will assess your situation and prescribe the appropriate dose of supplemental oxygen.
Oxygen saturation levels – what do they mean?
Oxygen saturation levels measure the degree to which the haemoglobin contained in the red blood cells (erythrocytes) has bonded with oxygen molecules. Oxygen is taken in by the lungs when we breathe in.
The two most common ways of assessing the saturation of oxygen in the blood are arterial blood gases (ABG) and pulsatile oxygen.
What does an ABG measure?
An ABG test measures how efficiently your lungs are bringing oxygen into the blood stream and removing carbon dioxide. Arterial blood gases are taken from an artery usually on the wrist. This procedure can be a little painful. The critical oxygen blood level is 55-60mmHg (SaO2), with readings below this level indicating the person is underoxygenated.
What does a pulse oximeter measure?
A pulse oximeter indirectly measures oxygen saturation levels. This non invasive process involves inserting a finger (can be used on the ear or a toe as well) into the device where a red light calculates the redness of the blood pulsing through the finger. The pulse oximeter measures the haemoglobin providing a mean saturation percentage (SpO2). A SpO2 of 90% (equivalent to SaO2 of 55-60mmHg) is considered to be the critical level. The underlying principle of the oximeter is that it measures the redness of the blood – the redder the blood the higher the oxygen saturation.
Factors impacting on pulse oximeter readings
Dirty fingers, nail polish, bright lights and poor circulation to the extremities will all alter the accuracy of a pulse oximeter reading.
So, which is better, arterial blood gases or pulse oximeter measures?
The pulse oximeter provides a quick indication of blood saturation levels, however the arterial blood gases will give the most accurate measure.