Oximetry neither to prescribe long-term oxygen therapy nor to screen for severe hypoxaemia

Abstract

Background and ObjectiveTranscutaneous pulse oximetry saturation (SpO2) is widely used to diagnose severe hypoxaemia and to prescribe long-term oxygen therapy (LTOT) in chronic obstructive pulmonary disease (COPD). This practice is not based on evidence. The primary objective of this study was to determine the accuracy (false positive and false negative rates) of oximetry for prescribing LTOT or for screening for severe hypoxaemia in patients with COPD.MethodsIn a cross-sectional study, we correlated arterial oxygen saturation (SaO2) and SpO2 in patients with COPD and moderate hypoxaemia (n=240), and calculated the false positive and false negative rates of SaO2 at the threshold of ≤88% to identify severe hypoxaemia (PaO2 ≤55 mmHg or PaO2 <60 mmHg) in 452 patients with COPD with moderate or severe hypoxaemia.ResultsThe correlation between SaO2 and SpO2 was only moderate (intra-class coefficient of correlation: 0.43; 95% confidence interval: 0.32–0.53). LTOT would be denied in 40% of truly hypoxemic patients on the basis of a SaO2 ˃ 88% (i.e., false negative result). Conversely, LTOT would be prescribed on the basis of a SaO2≤88% in 2% of patients who would not qualify for LTOT (i.e., false positive result). Using a screening threshold of≤92%, 5% of severely hypoxemic patients would not be referred for further evaluation.ConclusionsSeveral patients who qualify for LTOT would be denied treatment using a prescription threshold of saturation ≤88% or a screening threshold of ≤92%. Prescription of LTOT should be based on PaO2 measurement.

Global Initiative for Chronic Obstructive Lung Disease 2023 Report: GOLD Executive Summary

“…In severe ECOPD, blood gases should be checked frequently or as clinically indicated to monitor for carbon dioxide retention and/or worsening acidosis. Pulse oximetry is not as accurate as arterial blood gas measurement [ 139 ] and, in particular, may overestimate blood oxygen content among individuals with darker skin tones [ 140 ]. Venturi masks offer more accurate and controlled delivery of inspired oxygen than do nasal prongs [ 1 ].…”

Short-Term Oxygen Therapy Outcomes in COPD

“…Arterial blood gas measurement should be preferred to pulse oximetry to determine the need for LTOT. 31 If severe hypoxaemia persisted, STOT would then become LTOT.…”

Pulse Oximetry Misclassifies Need for Long-Term Oxygen Therapy in Chronic Obstructive Pulmonary Disease

“…Despite a lack of clinical evidence supporting its use in establishing a need for LTOT, approximate arterial oxygen saturation based on pulse oximetry (Sp O 2 ) was adopted into governmental and organizational guidelines ( 3 , 4 ). The current insurance reimbursement criteria for LTOT in the United States use Sp O 2 cutoffs of <88–89% as an alternative to Pa O 2 cutoffs (⩽55 mm Hg or ⩽59 mm Hg in the presence of pulmonary hypertension, cor pulmonale, right heart failure, or polycythemia) despite previous studies raising concern that using saturation thresholds to establish hypoxemia for patients with COPD could lead to misclassification ( 5 ).…”

“…They showed that Sp O 2 overestimates arterial oxygen saturation among smokers and individuals self-identifying as Black, although the latter did not reach statistical significance, possibly because of a lack of statistical power. Together, the use of oxygen saturation rather than Pa O 2 and the reliance on pulse oximetry to estimate oxygen saturation likely amplify the misclassification of severe hypoxemia ( 5 ).…”