PURPOSE: Oxygen saturation based on pulse oximetry (SpO2) is commonly used to titrate oxygen therapy using 90% as the target for an acceptable lower limit of oxygen saturation. This study was performed at LDS hospital where the altitude is 4600 feet. Pulse oximeters are typically thought to measure oxygen saturation within ± 4 % of the measured arterial saturation which is the gold standard. However, the variability may by much higher.
METHODS: This was a retrospective computer based analysis of a data set containing 27,594 paired samples of measured SaO2 and SpO2. The Radiometer ABL 700 and 800 Blood gas analyzer was used to measure the fractional hemoglobin concentration of the arterial blood samples. Data for adult patients were obtained sequentially between November 2001-March 2004. All arterial blood gas samples that had a SpO2 recorded at the time of the blood gas draw were included in the analysis. The SpO2 was obtained with an ear or finger probe using Masimo, Nellcor or Ohmeda equipment without controlling for version of software from the manufacture.
RESULTS: The Sa02-Spo2 percent difference were [0-2], 17,129 (62)%, Acceptable, [3-6], 9668 (35)% Marginal, [7-10], 407 (1.5)% Unacceptable. Further, there were 390 (1.4)% erroneous paired data that were unusable. Sample size was 27,204.
CONCLUSION: 97% of the time the difference betwen the Spo2 and Sa02 was ≤; 6%. 3% of the time difference between Sp02 and Sa02 was ≥ 7% and as high a 12%. The differences increased as carboxyhemoglobin increased. This data raises concerns about using pulse oximetry as a stand alone test to titrate oxygen in the adult patient population at 4600 in 3% of our patient population.
CLINICAL IMPLICATIONS: These finding indicate that using Sp02 to titrate oxygen delivery may be acceptable 97% of the time. In 3% of the cases the use of Sp02 alone to titrate oxygen delivery without the conformation of measured arterial saturation may leave acutely ill patients hypoxemic.
DISCLOSURE: Loren Greenway, No Financial Disclosure Information; No Product/Research Disclosure Information