The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts


S. Strizek, N. Hordvik, T. Hallberg, and J. Colombo Department of Pediatrics, University of Nebraska Omaha, Nebraska

The purpose of this study was to investigate the factors involved in the sometimes significant difference in ear vs. finger pulse oximetry readings in CF patients. A total of 154 sets of simultaneous oximetry readings were obtained using multiple probe sites. These included the right (R) and left (L) ear measured with the Ohmeda 3700 oximeter and the R and L index finger measured with both the Ohmeda 3700 and Nelloor N100 oximeters. The largest mean difference was between the L ear vs R finger (delta ear-finger) and was only 2.03%; however, the SD was large (6.52%). There was no significant correlation between delta ear-finger and the magnitude of finger clubbing (spearman rho=0.164, p=ns). There were no significant differences between the readings on the R and L ear or between the R and L finger when using the same oximeter. There was a consistent, small, but significant difference in readings between oximeters as measured on both fingers and was greatest on the right. The mean (SD) 02 SAT of the R finger = 93.31 (5.20) with the Nelloor vs. 92.49 (6.52) with the Ohmeda (p < 0.0001). Part of this difference can be attributed to the automatic correction by the Ohmeda for carboxy and met hgb. However, the biggest factor was O2 saturation. As the patient's right finger saturation decreased the delta ear-finger increased (pearson rho = -0.876, p < 0.001). In addition, the delta ear-finger also increased as the FVC and FEV1 decreased (pearson rho=-0.259 and -0.284, p < 0.01 and 0.01 respectively). Conclusion: The difference between ear and finger readings increases as patients become more hypoxemic. These differences are great enough to potentially impact the decision to use supplemental oxygen.


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