Pulse oximetry oxyhemoglobin saturation in patients with idiopathic pulmonary fibrosis

Pulse oximetry provides a non-invasive assessment of percentage of oxyhemoglobin saturation (SpO2).SpO2-pO2 correlation is strong in healthy subjects. Usually, respiratory failure in idiopathic pulmonary fibrosis (IPF) is not associated to hypercapnia and hypoxemia reflects disease severity. Aim of the present study was to validate the use of fingernail pulse oximetry SpO2 as a non-invasive method to monitor respiratory conditions in patients with IPF. We performed a retrospective study from our IPF database to assess SpO2 vs. pO2 correlation in patients with IPF in different stages of their disease. We collected 208 consecutive arterial blood gas analysis (ABGA) and fingernail SpO2 measurement in 51 patients with IPF. All data were collected while patients were at rest. Fingernail SpO2 was 91.98±5.60 (%) and pO2 was 66.29±12.51 (mmHg) (M±SD). A significant correlation was found between fingernail SpO2 and oxyhemoglobin saturation directly assessed by blood gases analyzer (r 0.74, p<0.0001, Bland-Altman test bias 0.12, SD of bias 2.89). Fingernail SpO2 showed a significant positive correlation with arterial pO2 (r 0.71, p<0.0001). SpO2-pO2 correlation still was statistically significant in IPF patients with oxygen supplementation (FiO2 29.9±6.7) at the moment of collecting data (n= 95, r 0.60, p<0.0001). In IPF patients fingernail SpO2 is a reliable, non-invasive and repeatable measure that highly correlate with arterial pO2 and is indistinguishable from oxyhemoglobin saturation in ABGA. SpO2-pO2 correlation is not influenced by oxygen supplementation. Fingernail SpO2 should be considered suitable and safe in monitoring patients with IPF also in advanced stages while in oxygen-therapy.