The ear as an alternative site for a pulse oximeter finger clip sensor

Finger clip pulse oximetry sensors are commonly used to obtain functional oxygen saturation readings (S(pO2)), but these sensors may perform poorly if the digit is poorly perfused or there is excessive hand movement. I have increasingly witnessed clinicians obtaining S(pO2) readings by placing the finger clip sensor on the patient's ear when an S(pO2) reading cannot be obtained from a finger.

Determine if reliable S(pO2) readings can be obtained from a finger clip sensor placed on the ear.

This was a prospective study with patients undergoing pulmonary function testing. The calculated functional oxygen saturation values from arterial blood gas analysis (S(aO2)) were compared with S(pO2) readings from a finger clip sensor placed on a finger (finger S(pO2)) and on the upper portion of an ear (ear S(pO2)). S(pO2) data were included in the study only if (1) the pulse rate from finger S(pO2) and ear S(pO2) differed by < or = 5 beats/min and (2) the photoplethysmographic waveform was stable and acceptable.

Data were obtained from 30 adult white patients. The number of S(pO2) readings that differed from the S(aO2) values by > or = 3% were 1 (3.3%) finger S(pO2) reading and 24 (80%, 95% CI 61%-92%) ear S(pO2) readings (p < or = 0.001). Bland-Altman analysis showed better agreement between S(aO2) and finger S(pO2) (mean +/- 2 SD limits of agreement -2.35 to 2.35) than between S(aO2) and ear S(pO2) (limits of agreement -7.24 to -0.08) or finger S(pO2) and ear S(pO2) (limits of agreement -7.56 to -0.23).

A pulse oximeter finger clip sensor placed on the ear does not provide clinically reliable S(pO2) readings.