Ability to continuously and transcutaneous monitor the functional oxygen saturation of hemoglobin in arterial blood (SaO2).
Pulse oximetry is so widely prevalent in medical care that it is often regarded as a fifth vital sign.
It is important to understand how the technology functions as well as its limitations because erroneous readings can lead to unnecessary testing.
Frequent false alarms in the intensive care unit can also undermine patient safety by distracting caregivers.
Pulse oximeter measure
Although pulse oximetry is accurate in reflecting one-point measurements of SaO2, it does not reliably predict changes in SaO2, particularly in intensive care unit (ICU) patients.
The conventional pulse oximeters use transmission sensors in which the light emitter and detector are on opposing surfaces of the tissue bed.
These sensors are suitable for use on the finger, toe, or earlobe; when tested under conditions of low perfusion, finger probes performed better than other probes.
Recently, pulse oximeter probes that use reflectance technology have been developed for placement on the forehead.
The reflectance sensor has emitter and detector components adjacent to one another, so oxygen saturation is estimated from back-scattered light rather than transmitted light.
Pulse oximeter spo2 range
In critically ill patients with low perfusion, the bias and precision between SpO2 and SaO2 were lower for the forehead reflectance probe than for the finger probe.
The superiority of forehead reflectance probes over conventional digital probes, however, was not observed in patients with acute respiratory distress syndrome during a positive end-expiratory pressure (PEEP) recruitment maneuver.
The response time of conventional oximeter probes varies; ear probes respond quicker to a change in O2 saturation than finger probes.
A recent study compared the response time of the conventional finger probe with the reflectance forehead probe in patients undergoing general anesthesia.
The lengths of time it took to detect a decrease in SpO2 to 90 % after apnea was induced (desaturation response time) were 94 seconds for the forehead probe and 100 seconds for the finger probe.
After mask ventilation was started, the lengths of time it took to detect an increase in SpO2 to 100 % (re-saturation response time) were 23.2 seconds for the forehead probe and 28.9 seconds for the finger probes.
The forehead probe monitors O2 saturation from the supraorbital artery in which blood flow is abundant and is less likely to be affected by vasoconstriction than is a peripheral artery.
Pulse Oximeters: Answering Your Frequently Asked Questions
The accuracy of some low-cost pulse oximeters tested performed similarly to more expensive, ISO-cleared units when measuring hypoxia in healthy subjects.
As per the studies, your right hand’s middle finger shows the best results. Make sure to take off any nail polish and avoid using cold fingers as the readings may not show correctly.
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