Do you often feel out of breath, or as if you are constantly trying to catch your breath? There may be a physiological reason why your body may increase your breathing rate. This may be because there is not enough oxygen within your cells and throughout the body.
Typically, you should expect an oxygen saturation level of between 94-99%. Anything below 90% would be of concern and should be checked over by a physician.
What is an Oximeter?
An Oximeter measures theoretical oxygen being carried within the blood stream. It does so by measuring your pulse. To understand how the pulse indicates oxygen saturation we need to go back to the beginning.
Oxygen in the blood
When we inhale oxygen from the air it travels down into our lungs. Through the windpipe (trachea), into the bronchi, bronchioles and alveoli. Around these alveoli are small blood vessels called capillaries. Through the capillaries, are travelling red blood cells. As the red blood cells pass the alveoli there is a process of gas exchange (see diagram below). One of the roles of red blood cells is to carry oxygen and carbon dioxide around the body using haemoglobin. As the red blood cells pass the alveoli they change from carboxyhemoglobin to oxyhaemoglobin. Normally, only 75% of our red blood cells are saturated at any one time.These then travel to active organs and cells to start the process of respiration.
How does an Oximeter work?
An oximeter passes a beam of light through the finger to a sensor on the other side. This light detects arterial blood flow which is presented on the monitor under ‘HR’, standing for Heart Rate. This red light detects which of the haemoglobin is in arterial blood. This helps to determine the oxygen saturation of the red blood cells, represented as ‘SpO2’.
Always read the instructions before use.
When might you need an oximeter?
Conditions that may affect oxygen levels include:
- Pulmonary disorders like Chronic obstructive pulmonary disorder (COPD), emphysema, bronchitis, or a collapsed lung or pulmonary embolism.
- High altitude
- High strength pain medication that may supress normal breathing
- Sleep apnea
- Pulmonary fibrosis
- Heart disease or heart defects
COVID and Oxygen Saturation
Since the beginning of the COVID pandemic, NHS England has advised that medical intervention is necessary if oxygen saturation levels began to fall. In the British Medical Journal. it was stated that some people were suffering from silent hypoxia. This is a phenomenon whereby patients have seriously desaturated blood, but without any of the obvious symptoms, such as shortness of breath and fatigue. The following quote has been extracted from the BMJ:
‘Nigel Watson, chief executive of Wessex Local Medical Committees, which is expected to be one of the first areas to implement the monitoring at home scheme, told The BMJ that the evidence was now fairly strong that if oxygen saturation fell to 94% or 93% the mortality risk increased to around 13%, and if it fell below that level, the risk would increase to about 28%.’
This discussion has not been shared to scaremonger or frighten the general public. However, during this pandemic the oximeter has become a first aid essential. It’s likened to having a thermometer or plasters in your first aid kit. An oximeter is one of the precautionary measures that you can take to detect symptoms of the COVID-19 and reduce asymptomatic spreading of the virus.
For more information on Oximeters from public health bodies please check the resources below:
- British Medical Journal - https://www.bmj.com/content/371/bmj.m4151
- NHS - https://www.england.nhs.uk/coronavirus/wp-content/uploads/sites/52/2020/06/Pulse-Oximeter-Easy-Read-final-online-v4.pdf
- NHS- https://www.england.nhs.uk/coronavirus/wp-content/uploads/sites/52/2020/12/C0719_COVID-Isolating-at-Home-Safety-Netting-Leaflet-Revised-FINAL-171220.pdf
- Londonwide LMC - https://www.lmc.org.uk/visageimages/Covid-19/Guide%20to%20using%20pulse%20oximeters%20during%20Covid-19%20pandemic.pdf