Pulse oximeters are quick, inexpensive and needle-free - making them a great tool to measure the amount of oxygen in your blood. It helps to gauge whether your heart and lungs are functioning properly to supply enough oxygen to your body.
Pulse oximeters are commonly used in situations involving:
- Heart attack
- Heart failure
- Chronic obstructive pulmonary disease (COPD)
- Lung cancer
- Sleep apnea
- And most recently, COVID-19
Photo by SM Health Care
HOW DOES IT WORK?
The small, clip-like device will be placed on your finger, toe or ear.
The pulse oximeter uses a special type of light to see how much oxygen is in the red blood cells travelling through the blood vessels under your skin.
In just a few seconds, the device will show your heart rate and oxygen saturation level -- the percentage of your red blood cells carrying oxygen.
Healthy oxygen saturation levels (SPO2) should be between 95% to 100%.
Healthy pulse rates should be between 60-80 beats per minute.
Photo by SM Health Care
WHAT AFFECTS THE ACCURACY OF A PULSE OXIMETER?
1. Manicures or Pigment on Finger
- The colour from the nail polish or pigment on the finger (e.g. henna) can absorb light emitted by the oximeter.
- This interferes with the detection of oxygenated haemoglobin.
- The oximeter may detect a pulse but is unable to measure SPO2 due to the pigment blocking the signal. 
- Make sure to use a finger that does not have nail polish or pigment for pulse oximetry. Otherwise, clip the pulse oximeter on the toe or ear lobe.
2. Bright Light
- Bright light such as sunlight or the operating light on the probe may interfere with the light detector and cause inaccuracy.
- Make sure to avoid direct bright light on the probe.
- Motion and movement can interfere with signal detection and interpretation of the signal by the device because of an unstable waveform. 
- Make sure to sit still and do not move the part of your body where the pulse oximeter is located.
4. Skin Pigmentation
- A study has found that darker skin pigmentation may get less accurate measurements.
- African-American patients had nearly three times the frequency of low oxygen levels in the blood as detected by blood gas measurements but not detected when using a pulse oximeter, when compared to Caucasian patients.
5. Skin Temperature
- The pulse oximeter is less accurate at cold temperatures as it may fail to register a signal.
- Make sure your hand is warm, relaxed and held below the level of the heart when taking a reading.
6. Skin Thickness
HOW TO CHECK IF A PULSE OXIMETER IS WORKING PROPERLY?
Here are a few ways to check if your pulse oximeter is working properly.
1. Check on another person who is healthy
- As mentioned earlier, a healthy SPO2 reading should be between 95% to 100%, with a pulse rate of 60-80 beats per minute.
2. Check on another inanimate object
- Recently, we’ve seen viral videos about how some of the pulse oximeters have been tested on soft toys and shockingly, readings were shown for these soft toys (which clearly do not have oxygen saturation nor a pulse).
- If the pulse oximeter shows a reading even when it is tested on an inanimate object, do not purchase the pulse oximeter.
Here are some tips to make sure you choose the right pulse oximeter -- one that is accurate.
- Make sure to select pulse oximeters that are sold by regulated brands and companies.
- Make sure to select pulse oximeters that are approved by governing bodies to ensure good quality control.
- Make sure to verify and check for certifications for the pulse oximeter that you are thinking of buying.
SM Health Care is a company registered with the Perbendaharaan Malaysia Sabah (PMS). We are a medical and healthcare solution provider, and we have been supplying to hospitals and clinics for more than 10 years.
We have carefully selected pulse oximeters that accurately measure oxygen saturation levels and pulse rates because we believe in providing reliability, consistency and nothing but products of the best quality.
Here are the some of our pulse oximeters: