How Does a Pulse Oximeter Work

Oximetry is a non-invasive technique that is used to check the level of oxygen in the human body through sensors. It monitors the levels of oxygen saturation in the blood through visible infrared lights which indicates whether a patient has respiratory or cyanotic congenital heart disease. The oxygen level in the blood should be above 95%, which gets significantly lower in case one suffers from such diseases and depending upon the severity of the disease. Through this technique, doctors can have a better insight about the patient’s health condition and severity. It can be performed at the hospital or in the comfort of your own home. The time of observation depends on the patient’s condition and the
required testing. For problems related to sleeplessness and lungs, overnight oximetry testing is done as well.

How Does a Pulse Oximeter Work?

The technology of a pulse oximeter is based on the principles of spectrophotometry. It is defined to be the “absorption of red (absorbed by deoxygenated blood) and infrared (absorbed by oxygenated blood) light of the systolic component of the absorption waveform correlates to arterial blood oxygen
saturations.”  The final reading depends on the average of the three readings of relative light absorption which occurs several times per second. The testing is done by attaching two light emitting diodes opposite to a detector that detects the oxygenation of the blood. The probes are usually attached on a finger or an ear;
places where light can easily pass through the tissue. Sometimes, the forehead is also used. However, a study suggests that the earlobes are not a preferable place to detect blood oxygenation levels.

How to Use It?

You will have to clip the pulse oximeter to a fingertip or earlobe or anyplace where the light can shine through the blood flowing in the arteries. Make sure that the reading given by a pulse oximeter is accurate. It is very essential because in some cases, the oximeter gives a wrong reading or displays nothing at all. To check the accuracy of the readings given by a pulse oximeter, compare it to the pulse you take manually. Both the observations should show correspondence. If they don’t, then this indicates an error in the readings given by the device. This can be caused by multiple reasons like:

  •  Nail polish on the nail of the finger the detector is attached to
  •  The patient moving excessively
  •  Deficiency of iron in blood, a condition called Anemia
  •  Seizures of certain kinds, and so on

The person should remain calm and still during the assessment. Nail polish should be taken off or the device should be attached to a body part other than the fingertips.

How to Interpret the Readings of a Pulse Oximeter?

You heart rate would also be recorded by the pulse oximeter, which is quantified in beats per minute.  For an elderly, the normal count is 90 while in adults, 60-80 BPM is considered to be normal 100 BPM and above is rapid and below 60 is slow. The heartbeat of children aged between 5-12 years of age is considered to be normal in the range of 60-120, while it is 80-150 for children in the age group of 1-5 years. For infants, it is normal for them to have 120-150 beats per minute.