The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

Improved Accuracyof the Masimo SET® Oximeter (MSO) Increases Caregiver Confidence in SaturationValues

Stephanie K. Rostow, RRT,Lead Therapist, Charles G. Durbin, Jr., MD, Professor of Anesthesiology andSurgery, University of Virginia Health System, Charlottesville, Virginia, USA

During a prospective study of theimpact of improved oximetry on clinical practice, we found that caregivers morerapidly weaned cardiac surgery patients from a high FiO2 while obtainingfewer ABGs, when they had access to data from an MSO as compared to a conventionalpulse oximeter (CPO) (Ohmeda 3740). [1,2]. In this report we examine the relationshipbetween saturations determined from clinically indicated ABGs and the saturationsreported simultaneously to evaluate their accuracy.

Methods: After obtainingconsent, 86 adult patients were studied following CABG surgery. On arrival inthe ICU, both a CPO and a MSO were attached to the same hand and the outputfrom both monitors continuously recorded until 4 hours following extubationor for a maximum of 24 hours. Patients were randomly assigned to display onlyone device to the bedside caregivers with the other device ?blinded?. No clinicalinterventions were changed. Any time an ABG was obtained, comparison of thesaturation reported for each oximeter and that calculated from the ABG was made.

Results: 283 ABGs were studied,134while the MSO was unblinded and 149 while the CPO was unblinded. The bias (mean+ sd) was calculated as the difference between the SpO2 andthe average of the SpO2 and SaO2, for each oximeter, forall blood gas samples obtained. For the MSO the difference was .53 ± 1.7%; forthe CPO -.82 ± 2.8%, p<.05. Limiting analysis to unblinded data failed toimprove the results for the CPO. The frequency distribution of the bias wascounted and grouped (Figure). MSO produced a bias >5% significantly lessfrequently than CPO; 3% versus 15% of all ABGs (p<.05).

Conclusions: The MSO had asmaller bias then CPO. The CPO had more errors greater than 5% saturation. Thisimproved accuracy, as demonstrated by the smaller average bias and the narrowerrange of biases seen with the MSO device, is one reason why clinicians had greaterconfidence in the MSO data, weaned patients faster and obtained fewer confirmatoryABGs in our study patients.


1. Durbin, Jr. CG, Rostow SK: Improvedpulse oximetry changes caregiver practice patterns: Masimo SET ® vs. conventionalpulse oximetry. Respir Care 45(8); 986, 2000.

2. Durbin, Jr. CG, Rostow SK: Pulseoximetry performance can affect

caregiver time utilization. Anesthesiology93 (3A); A556, 2000


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