The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

ACCURACY OF FIVE PULSE OXIMETERS ON MECHANICALLY VENTILATED ICU PATIENTS.

Kelly Jager RRT, Colya Kaminiarz RRT, Dean Chittock MD.

Introduction: Pulse oximetry is so commonly used now that it is sometimes referred to as the 5th vital sign. Numerous studies have been conducted on their accuracy, however, many of these published studies have been carried out on healthy volunteers in a controlled setting. The primary purpose of this study was to compare the accuracy of 5 different pulse oximeters (Simed, Datex, Ohmeda, Nellcor 3000 and Nellcor 180) and secondarily to compare the Simed, our standard pulse oximeter already in-house, in relation to the others. Methods: One of the 4 other evaluation pulse oximeters was used in 4 different groups of mechanically ventilated ICU patients already having a Simed oximeter in place. The 2 probes were randomly placed on patients fingers, and data recorded for pulse correlation, signal strength, and waveform quality. The SpO_{2} from both pulse oximeters was recorded and an arterial blood gas drawn to determine the true HbO_{2}. The bias (SpO_{2} - HbO_{2}) and precision (standard deviation of the mean difference) was recorded. Results: Results are shown in Table 1. The mean bias and precision for all 5 pulse oximeters was 3.8 ± 0.71 with a range in bias of 13 to 0. There was no difference in bias between oximeters. There was, however, a statistical difference in bias between the different Simed oximeters used (8 different units compared to 1 of each of the other evaluation oximeters).

Table 1. Mean bias for 5 pulse oximeters

Nellcor 180 Ohmeda Datex Nellcor 3000

n = 17 11 16 10

*patient HbO_{2} 0.87-0.99 0.92-0.99 0.92-0.99 0.84-0.99

bias & precision 4.06±2.63 3.82±1.08 3.56±1.71 3.70±3.23

Simed (b&p) 2.29±1.72 4.09±2.34 3.81±2.07 4.82±2.56

* range of HbO2's tested in each patient group

n= number of measurements taken in each patient group

b&p = bias & precision

Discussion: The accuracy of all 5 pulse oximeters was less than the manufacturers specifications when used in this limited number of critically ill, mechanically ventilated patients. One device (Simed), when tested in 4 random patient groups, demonstrated a bias that varied from 2.29 to 4.82. Further study is needed to determine if this variability is related to a specific critically ill patient population.

OF-97-039

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