Article

The accuracy of pulse oximetry in the emergency department.

Division of Emergency Medicine, University of Utah Medical Center, Salt Lake City, USA.
American Journal of Emergency Medicine (impact factor: 1.98). 08/2000; 18(4):427-31. DOI:10.1053/ajem.2000.7330 pp.427-31
Source: PubMed

ABSTRACT The objective of this retrospective study was to identify factors affecting the accuracy of pulse oximetry in the ED. Over a 3-year period, 664 consecutive emergency department (ED) patients had simultaneous arterial blood gas (ABG) and pulse oximeter readings taken. Pulse oximeter saturations (SpO2) were compared with ABG CO-oximeter saturations (SaO2) for accuracy. Multiple variables including age, sex, hemoglobin, bicarbonate, pH, and carboxyhemoglobin (COHb) were analyzed to see if they affected SpO2 accuracy. ROC curves were used to determine the best pulse oximeter threshold for detecting hypoxia. Using multivariate analysis, COHb was the only statistically significant factor affecting the accuracy of pulse oximetry. In patients with COHb <2%, SpO2 overestimated SaO2 by more than 4% in 8.4% of cases. In patients with COHb > or = 2%, SpO2 overestimated SaO2 by more than 4% in 35% of cases. The best pulse oximetry threshold for detecting hypoxia is 92%. At this threshold, if COHb is <2%, pulse oximetry has a sensitivity of 0.92 and specificity of 0.90. If COHb is > or =2%, sensitivity is 0.74 and specificity is 0.84. For patients likely to have a COHb < 2, pulse oximetry is an effective screening tool for detecting hypoxia. However, more caution must be exercised when using pulse oximetry in patients likely to have a COHb > or = 2%.

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Keywords

3-year period
 
664 consecutive emergency department
 
ABG CO-oximeter saturations
 
COHb
 
detecting hypoxia
 
effective screening tool
 
Multiple variables
 
multivariate analysis
 
patients
 
patients likely
 
pulse oximeter readings
 
Pulse oximeter saturations
 
pulse oximeter threshold
 
pulse oximetry
 
pulse oximetry threshold
 
retrospective study
 
ROC curves
 
SaO2
 
SpO2 accuracy
 
SpO2 overestimated SaO2
 

W W Lee