The Ear as an Alternative Site for a Pulse Oximeter Finger Clip Sensor

Abstract

BACKGROUND:

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.

OBJECTIVE:

Determine if reliable S_pO2 readings can be obtained from a finger clip sensor placed on the ear.

METHODS:

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 ≤ 5 beats/min and (2) the photoplethysmographic waveform was stable and acceptable.

RESULTS:

Data were obtained from 30 adult white patients. The number of S_pO2 readings that differed from the S_aO2 values by ≥ 3% were 1 (3.3%) finger S_pO2 reading and 24 (80%, 95% CI 61%–92%) ear S_pO2 readings (p < 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).

CONCLUSION:

A pulse oximeter finger clip sensor placed on the ear does not provide clinically reliable S_pO2 readings.