When we breathe, oxygen enters our lungs and passes into our bloodstream where it is collected by red blood cells and carried around the body. An oximeter can be used to check how well the oxygen is binding to your red blood cells (expressed as SpO2) through your finger. Previously used pre and post-exercise, pre and post-operations and to monitor respiratory conditions, they have become more common since the COVID-19 pandemic.
Oximeters are easy and painless to use, the device clips onto your finger and uses infrared light refraction to measure oxygen levels. It is important to note that some people with COVID-19 will appear well but have low oxygen levels and others may have symptoms of fever, muscle aches and tummy upset but have normal oxygen levels. Therefore, they shouldn’t be used to diagnose infection.
Oximeters are being used as a monitoring tool for COVID-19 positive people isolating at home, to check if a person has low blood oxygen levels (hypoxia). If a person’s oxygen levels drop, this can indicate the infection is worsening and more help should be sought. Other symptoms of laboured breathing, severe chest pain, restlessness or discomfort, uncontrollable coughing or pale / bluish lips or fingers also need emergency care. It is important to have a reference of your normal oxygen levels, but hypoxia is usually defined as oxygen saturation below 94% and severe disease in levels below 92% in a healthy person. Pulse oximeters also measure your heart rate as another marker to check. Your pulse should sit between 50-99 beats/minute and you should talk to your doctor if it is 100-119 beats/minute or if over 120 beats/minute, call 111 for urgent care.
Readings should be taken on a warm finger and repeated on the other hand. Sit and rest before taking the measurement. Remove fake nails or polish and wash your hands. Have them at waist level and squeeze to open the device. Insert your middle finger to the end of the meter, keep still for 1-2 minutes until your pulse and oxygen readings remain steady for at least 5-seconds. Oximeters allow for self-monitoring but should always be used alongside medical care.
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