We studied the utility and drawbacks of the earlobe probe sensor on the percutaneous arterial oxygen saturation (SpO2) measurement. The SpO2 from the earlobe, forehead and finger sensor were measured simultaneously, and then changes of SpO2 readings induced by medical interferences and influence by the sensor attachment were compared among three types of sensor. The SpO2 from the earlobe sensor responded to the rapid change of patient clinical condition as well as from the forehead and finger sensor. The pulse wave signal from the earlobe sensor was more stable compared to those from forehead and finger sensor, but the time to display SpO2 readings after the earlobe sensor attachment was similar to the forehead sensor and it took longer than that in case of the finger sensor attachment. Some cases were difficult to measure SpO2 because of extremely thin earlobe and edema of earlobe. The long-term attachment of the earlobe sensor did not leave any surface imprint on the patient skin that is often found with the use of forehead and finger sensor. Also no patient had removed the earlobe sensor on a voluntary basis. While the SpO2 measurement with the earlobe sensor may be affected by several factors such as the earlobe shape and the peripheral circulation, it is the least painful for the patient. The active utilization of the earlobe sensor in clinical practice is promising as a new approach of the SpO2 measurement.
