Pulse oximetry is the measurement of the oxygen saturation level of the blood. The oxygen from the lungs is carried to the cells in various organs of the body through the hemoglobin present in the red blood cells. The percentage of oxygen present in the hemoglobin is called oxygen saturation and is denoted as SpO2. This is a non-invasive method which is performed using a pulse oximeter. A pulse oximeter is attached to the fingertip, toes, or earlobe by its probe. The pulse oximeter displays the oxygen SpO2 in percentage and the pulse rate. The pulse rate is the number of heart contractions in a minute.
Working of a pulse oximeters
Pulse Oximeters are photoelectric devices, which means they use light to measure oxygen concentration in the blood. One side of the probe attached to the finger has LED emitters that shine two wavelengths of light, infrared and visible red light, through the finger. The other side of the clip has a detector which catches the light emerging from the finger. The pulse oximeter calculates the amount of light passed through the blood and the amount of light absorbed by the oxygen present in the blood to determine the oxygen concentration in the blood and displays the figure in percentage. A complex equation is used by the device to calculate the oxygen level.
The accuracy of pulse oximeters can be short by about 2% either way. For example, if a pulse oximeter gives a reading of 90% oxygen concentration, then the actual level is between 88% and 92%. There are a number of factors that can adversely affect the accuracy of pulse oximeters. These include interference caused by external light, poor blood circulation, low body temperature, changes in pulse, high bilirubin levels, lipids in blood plasma, and changes in pulse.
Benefits of pulse oximeters
Pulse oximeters are used to monitor a number of pathological conditions that reduce blood oxygen levels. These include lung cancer, anemia, chronic obstructive pulmonary disease, asthma, pneumonia, and congenital heart disease. Pulse oximeters are also used during medical emergencies, which cause a sudden drop in the blood oxygen level. They include choking, suffocation, drowning, inhalation of poisonous chemicals, allergic reactions, and cardiac arrest.
Pulse oximeters are also used to assess the efficacy of lung medicines, monitor oxygen saturation levels of a patient under general anesthesia, monitor oxygen levels during or after surgical procedures, and determine a person’s ability to tolerate physical activities.