Comparison of SpO2 values from different fingers of the hands

Pulse oximetry is a frequently used tool in anesthesia practice. Gives valuable information about arterial oxygen content, tissue perfusion, and heartbeat rate. In this study, we aimed to provide a comparison of peripheral capillary hemoglobin oxygen saturation (SpO2) values among every finger of the two hands. Thirty-seven healthy volunteers from operative room stuff between the ages of 18–30 years were enrolled in the study. They were monitored after 5 min of rest. After their noninvasive blood pressure, heart rate, fasting time and body temperature were measured, SpO2 values were obtained from every finger and each of two hands fingers with the same pulse oximetry.

All the SpO2 values were obtained after at least 1 min of the measurement period. A total of 370 SpO2 measurements from 37 volunteers were obtained. The highest average SpO2 value was measured from the right middle finger (98.2 % ± 1.2) and it was statistically significant when compared with the right little finger and left middle finger. The second highest average SpO2value was measured from the right thumb and it was statistically significant only when compared with the left middle finger (the finger with the lowest average SpO2 value) (p < 0.05). The spo2 measurement from the fingers of both hands with the pulse oximetry, the right middle finger, and right thumb have statistically significantly higher value when compared with a left middle finger in right-hand dominant volunteers. We assume that the right middle finger and right thumb have the most accurate value that reflects the arterial oxygen saturation.

The difference of SpO2 recordings between different fingers may not be clinically important, but this knowledge may be valuable in conditions with poor peripheral perfusion. Dominant hand and higher perfusion may explain the highest value in R3. But, the explanation of the lowest value in L3 is a little complicated. In the non-dominant hand, the size of the finger may become a negative contributing factor that determines the SpO2 recording.

Higher perfusion in the middle finger seems reasonable to expect the highest and most accurate SpO2value. According to the results of our study, we believe that the middle finger of the dominant hand has the highest and possibly the most accurate SpO2 measurements. The highest SpO2 value can be taken as the most accurate value that reflects the arterial oxygen saturation (SaO2). Because there may be contributing factors that can decrease the SpO2 recording measured by a pulse oximeter lower than SaO2, but there is no contributing factor that can increase the SpO2 recording higher than SaO2 (when a carbon monoxide poisoning like condition does not exist).

The main limitation of our study was the leak of arterial blood gas analysis during SpO2 measurements for determining the accurate value. Another limitation of our study was that we did not have adequate left-hand dominance volunteers. Further studies can be made with an adequate number of left-hand dominance volunteers or corroborated by arterial blood gas analyses and PI parameters.

In conclusion, SpO2 measurement from the fingers of both hands with the pulse oximeter, the right middle finger and right thumb have statistically significantly higher value when compared with a left middle finger in right-hand dominant volunteers. We assume that the right middle finger and right thumb have the most accurate value that reflects the arterial oxygen saturation.