What is Pulse Oximetry, What Does It Do & the Factors That Can Affect the Accuracy of a Pulse Oximetry?

What is Pulse Oximetry and What Does It Do?

Pulse oximetry is a device that is usually clipped to the finger to gauge the blood flow and to measure the amount of oxygen present in a person’s blood.(4) The oxygen is filtered through the lungs and transported all over the body through blood more specifically the hemoglobin in red blood cells. Pulse oximetry helps in determining the percentage of oxygen present in hemoglobin, which is known as oxygen saturation. Oxygen saturation is an indicator of the amount of oxygen the organs are getting from blood.

Patients suffering from cardiovascular or respiratory illness; children and patients with infections may need to use pulse oximetry to monitor and measure their oxygen levels in the blood.

Why is Oxygen So Important?

Our body and its organs and tissues need oxygen for survival. If there is any dearth of oxygen, then the body does not function properly and there is death of the cells and tissues; all this results in acute symptoms that eventually results in organ failure and death.(1)

What Are The Normal Oxygen Saturation Levels?

The normal levels of oxygen saturation are about 95 to 100%. If the levels of oxygen saturation drops under 90%, then it is considered abnormal and an emergency.(3)

What Are The Causes Of Reduction In The Oxygen Saturation Levels?

The causes for a drop in the oxygen saturation are many and consist of: choking, suffocation, infections, lung diseases, drowning, heart failure or other heart conditions; inhaling poisonous chemicals; general anesthesia; allergic reactions and sleep apnea.

The Functioning of Pulse Oximetry(4)

As mentioned before, the hemoglobin present in the red blood cells is responsible for distributing oxygen throughout the body. The pulse oximeter is a clip-on device that quantifies oxygen saturation level. The pulse oximeter can be attached to a finger, toe, a wrist or any part of the body that can tabulate the blood circulation within the body.(3)

What a Pulse Oximeter does is throw a light through a transparent part of the skin and this light shines via a detector that is situated on the opposite side of the skin. If the pulse oximeter is clipped to a finger, then one side of the pulse oximeter clip throws the light and the other side of the pulse oximeter clip detects the light. The amount of light that gets absorbed by the blood shows the level of oxygen saturation in the patient. A pulse oximeter cannot directly quantify the oxygen saturation; however, it uses complex equation along with other data to assess the exact level of oxygen saturation in the human body.

What are the Benefits of Pulse Oximetry?

Monitoring Nighttime Saturation Levels In Sleep Apnea: People suffering from conditions or diseases that affect or interfere with the normal levels of oxygen saturation benefit greatly with having a Pulse Oximeter. For example, if someone is suffering from severe snoring or sleep apnea, then the sleep specialist will recommend the patient to use a pulse oximeter for measuring the nighttime saturation levels of the oxygen.

Assessing the Physical Capacity of the Patient: Pulse oximetry is also used by some doctors to assess how safe physical activity can be for people suffering from respiratory or cardiovascular problems. In some cases, the doctor may also recommend to wear a pulse oximeter during a workout. Pulse oximetry can also be used as a part of a stress test.

To Determine Effectiveness of Breathing Interventions(3): Pulse oximetry is also beneficial in providing feedback regarding the effectiveness of breathing interventions, such as ventilators and oxygen therapy.

Beneficial for Vulnerable Patients: Vulnerable patients, such as infants in neonatal intensive care units, may need to wear a pulse oximeter to alert the hospital staff if there is any reduction in the oxygen saturation of the baby.

Other Common Benefits Of Pulse Oximetry Are:

  • Alerting the hospital staff if there is a dangerous drop in the oxygen levels; especially in newborns and infants.
  • Pulse oximetry helps in monitoring the levels of oxygen saturation over a period of time.
  • Pulse oximetry helps in giving the doctors an idea regarding the need for supplemental oxygen for the patient.
  • For patients suffering from chronic cardiovascular or respiratory illnesses, pulse oximetry gives them a lot of peace of mind.
  • Pulse oximetry helps in monitoring the oxygen saturation levels in patients who are under anesthesia(6).
  • Pulse oximetry helps in detecting fatal side effects in patients who take drugs that affect oxygen saturation or breathing.
  • Pulse oximeter is available online to anyone who wants to monitor their oxygen levels at home.

Pulse oximeters are also being marketed to parents of newborn babies who are worried about sudden infant death syndrome (SIDS) and other accidents when the baby is sleeping to give some much needed peace of mind; however, there are no studies to prove that a Pulse Oximeter prevent SIDS or any other type of sleeping accidents in babies.(2)

What are the Risks of Pulse Oximetry?

Mild Skin Irritation: Pulse oximetry is a very easy to use device that is noninvasive with no severe risks for measuring oxygen saturation levels at home.(7)

However, some patients can develop minor issues such as skin sensitivity and redness with the use of Pulse Oximetry Clip.

Restriction of Blood Circulation: If the pulse oximetry device is very snug and if used for extended period of time, then there is a risk of cutting off of blood circulation/oxygen from the vessels surrounding the pulse oximetry. If the patient experiences any tingling, numbness or skin color changes, then he/she should notify the doctor immediately.

False Reading: The primary risk of using pulse oximetry is getting false reading regarding the oxygen saturation. The accuracy of reading of pulse oximeter depends on its fit. Any small changes in the positioning of the pulse oximeter can give inaccurate reading. If the patient rolls over in their sleep, then the pulse oximeter can become loose and give a false alarm.

False Alarms: Other factors, such as momentary breath-holding or change in sleeping position can also cause level of oxygen saturation to drop for brief periods; even if the drop is harmless and temporary, the pulse oximetry will give an alert.

Patients and caregivers who do not understand the function of pulse oximeter or if their doctors have not explained to them, then such type of situations of false alarm can cause unnecessary worry.

False Sense of Security: In an alternative scenario, some people may feel false sense of security with the use of pulse oximeter, which is not always good, as pulse oximeters do not necessarily give alerts for all types of oxygen problems and they definitely cannot be used as a substitute for other types of monitoring.

NOTE: It’s important to discuss the risks of using pulse oximeters with a doctor and maintain a journal of daily readings. Any fluctuations in the readings, especially with regards to environmental changes can indicate a health problem in some cases.

What are the Limitations or the Factors That Can Affect the Accuracy of a Pulse Oximetry?

  • Changes in the pulse affect the readings of the pulse oximetry.
  • Bilirubin levels also interfere with the pulse oximetry readings.
  • Carbon monoxide poisoning can also give inaccurate results on pulse oximetry.
  • Bright lights, nail polish, poor circulation, cold hands can also affect the accuracy of pulse oximetry.(3)
  • Lipids in blood plasma can affect the accuracy of pulse oximetry readings.
  • Patients who find difficulty in breathing, dizziness, shortness of breath or have other signs of oxygen deprivation need to seek prompt medical attention.

Conclusion

So, we can clearly conclude that a pulse oximeter is a very useful, handy and beneficial device to monitor the oxygen saturation levels; especially for people with chronic diseases who need long term monitoring at home.

With the spread of the very contagious Novel Corona Virus, the use of pulse oximeter has seen a sharp jump; especially for patients who are home quarantined with breathing issues from Covid-19, the pulse oximeter has been a boon for them to monitor their oxygen saturation levels from their home itself.(5)

References:

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