The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

EVALUATION OF MASIMO SET PULSE OXIMETRY IN PATIENTS IN WHOM CONVENTIONAL OXIMETRY FAILS TO PROVIDE RELIABLE MONITORING

Stephanie Rostow, RRT, Charles Durbin, Jr., MD, FCCM; University of Virginia Health System, Charlottesville, Va

INTRODUCTION- Pulse oximetry is an integral part of monitoring critically ill patients in the intensive care unit, operating room, recovery room, and other locations. It is in many of these critically ill patients, that pulse oximetry has been shown to fail to obtain a signal. The failure rate for conventional pulse oximetry has been reported to range from 7.2% to 9% of patients (1,2). This failure rate increases with patient acuity (2). New pulse oximetry technology, Masimo SET ® reports to have increased accuracy during low perfusion and noise conditions. We prospectively evaluated the ability of Masimo SET oximetry (MSO) to obtain reliable pulse oximetry values in patients in whom conventional pulse oximetry (CPO) failed.
METHODS- We prospectively evaluated MSO in our cardiac surgery critical care unit. Upon admission, patients in whom CPO (Ohmeda 3740) failed to obtain reliable saturation readings were enrolled. Unreliable readings were defined as complete inability of CPO to obtain a pulse signal or display of an obviously spurious saturation or pulse rate value on CPO. MSO was then applied and if MSO obtained a stable pulse oximetry reading, arterial blood gases were obtained for validation of the SpO2 and the pulse rate was validated by ECG heart rate.
RESULTS- Eight postoperative (CABG = 5, Ventricular Assist Device placement = 1,TAA = 1, CABG and AVR = 1) adult patients (age range 52 -- 81 years) were identified. In 7 of 8 (88%) patients MSO obtained pulse oximetry readings. The SpO2 difference (MSO to ABG) was 1.1 ± 1 % (mean ± S.D.) in these patients (see Table). In the one patient in whom we were unable to obtain MSO, we were also unable to obtain ABG data as he suffered cardiac arrest requiring CPR.

TABLE
Spurious Condition CPO SpO2 MASIMO SpO2 ABG SaO2
Failed SpO2 0 100 99
Failed SpO2 0 98 99
Failed SpO2 0 98 97
Failed PR (!) 89 92 93
Failed SpO2 "low quality signal" 99 99
Failed SpO2 "low quality signal" 98 97
Failed SpO2 "low quality signal" "pulse search" (*)
High SpO2 100 88 91
(!) lack of correlation between pulse rate and ECG heart rate, causing question of SpO2 accuracy
(*) patient expired prior to obtaining arterial blood gas

DISCUSSION- In 88% of patients, in whom CPO failed, Masimo SET pulse oximetry obtained accurate SpO2 values. This allowed for continuous, accurate monitoring of SpO2 via MSO in critically ill postoperative patients where CPO failed, thereby resulting in a significant increase in patient safety. It is interesting to note that conventional pulse oximetry failure may include situations when SpO2 values are inaccurately high (as in one patient in our study). Even in this situation MSO was able to obtain a reliable SpO2 value.
1. Anesthesiology 1996; 84: 859-64. 2. Anesthesiology 1993; 78: 436-44.
Some technical support and equipment was provided by the Masimo Corporation, Irvine, CA

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