How are pulse oximetry results interpreted in pulmonary function testing?

Updated: May 14, 2020
  • Author: Kevin McCarthy, RPFT; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Interpretation of oximetry studies, while seemingly simple, generally is not possible without characterizing oximeter accuracy by correlating SpO2 with at least one simultaneously obtained arterial oxygen saturation (SaO2). Laboratories should characterize the average oximeter bias (SpO2 – SaO2) through pooled data to better understand the limitations of using the oximeter but this does not eliminate the possibility that oximeter readings on individual patients may exhibit larger biases. While SpO2 readings greater than 95% make the probability of clinically significant hypoxemia unlikely, clinical suspicion of hypoxemia should initiate the examination of ABGs. The goal of titration of supplemental oxygen should be a stable SpO2 reading of 93% or higher. Arterial desaturation can be considered present when the pulse oximeter saturation falls more than 4% below the baseline reading.

The role of pulse oximetry in the Medicare guidelines for reimbursement for continuous supplemental oxygen therapy are demonstration of one of the following while at rest and breathing room air: PaO2 less than or equal to 55 mm Hg, SaO2 less than or equal to 88%, or SpO2 less than or equal to 88%.

If supplemental oxygen is prescribed at a flow rate of greater than 4 L/min, the results of a PaO2 or oxygen saturation (SaO2 or SpO2) taken on 4 L/min supplemental oxygen must be provided.

Patients may qualify for supplemental oxygen therapy reimbursement even if the PaO2 is greater than 55 mm Hg and the SaO2 or SpO2 is greater than 88% if one of the following conditions is met: (1) dependent edema due to congestive heart failure; (2) cor pulmonale documented by P pulmonale on an ECG or by an echocardiogram, gated blood pool scan, or direct pulmonary artery pressure measurement, and (3) hematocrit greater than 56%.

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