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Review
. 2022 Nov;10(11):1086-1098.
doi: 10.1016/S2213-2600(22)00058-3. Epub 2022 Aug 29.

Pulse oximetry for the diagnosis and management of acute respiratory distress syndrome

Katherine D Wick  1 , Michael A Matthay  1 , Lorraine B Ware  2
Affiliations
Review

Pulse oximetry for the diagnosis and management of acute respiratory distress syndrome

Katherine D Wick et al. Lancet Respir Med. 2022 Nov.

Abstract

The diagnosis of acute respiratory distress syndrome (ARDS) traditionally requires calculation of the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2/FiO2) using arterial blood, which can be costly and is not possible in many resource-limited settings. By contrast, pulse oximetry is continuously available, accurate, inexpensive, and non-invasive. Pulse oximetry-based indices, such as the ratio of pulse-oximetric oxygen saturation to FiO2 (SpO2/FiO2), have been validated in clinical studies for the diagnosis and risk stratification of patients with ARDS. Limitations of the SpO2/FiO2 ratio include reduced accuracy in poor perfusion states or above oxygen saturations of 97%, and the potential for reduced accuracy in patients with darker skin pigmentation. Application of pulse oximetry to the diagnosis and management of ARDS, including formal adoption of the SpO2/FiO2 ratio as an alternative to PaO2/FiO2 to meet the diagnostic criterion for hypoxaemia in ARDS, could facilitate increased and earlier recognition of ARDS worldwide to advance both clinical practice and research.

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Conflict of interest statement

Declaration of interests KDW has received research grant support from the US National Institutes of Health (NIH; 5T32GM008440-24). MAM has received research grant support from the NIH (HL134828, HL126456, HL140026, and 143896), the US Department of Defense, and Roche-Genentech for observational studies on acute respiratory distress syndrome; he reports consultancy fees from Citius Pharmaceuticals, Johnson & Johnson, Gilead Pharmaceuticals, Plant Therapeutics, and Novartis pharmaceuticals, outside of the submitted work. LBW has received research grant support from the NIH (HL103836, HL126176, HL158906) and the US Department of Defense, and grants or contracts from Genentech, Boehringer Ingelheim, and CSL Behring; she reports consultancy fees from Foresee, Merck, Citius Pharmaceuticals, Quark, and Boehringer Ingelheim, outside of the submitted work.

Figures

Figure 1
Figure 1
Oxyhaemoglobin dissociation curve An SpO2 of 90% corresponds to a PaO2 of approximately 60 mm Hg, and an SpO2 of 97% corresponds to a PaO2 of approximately 90 mm Hg. For SpO2 values higher than 97%, the curve is flat and PaO2 cannot be reliably estimated from SpO2. PaO2=partial pressure of arterial oxygen. SpO2=pulse-oximetric oxygen saturation.
Figure 2
Figure 2
Examples of how error in SpO2 measurement could lead to misdiagnosis or misclassification of ARDS Pulse oximeters are accurate to approximately 3%. In some cases, measurement error could result in misdiagnosis or misclassification of the severity of hypoxaemia. ARDS=acute respiratory distress syndrome. FiO2=fraction of inspired oxygen. PaO2=partial pressure of arterial oxygen. SaO2=arterial blood oxygen saturation. SpO2=pulse-oximetric oxygen saturation.
Figure 3
Figure 3
Example flowchart for enrolment of patients into clinical trials or studies using pulse oximetry Pulse-oximetric measurements can be used in studies of both mechanically ventilated patients with ARDS and patients on other modes of supplemental oxygen (eg, patients at risk of ARDS or non-ventilated patients with acute hypoxaemic respiratory failure). Pulse-oximetric indices should not be used if SpO2 is above 97% because the oxyhaemoglobin dissociation curve is flat above this value. High-quality pulse oximetry measurements should be made when the patient is at rest, at least 10 min after any changes in FiO2, and when there is a high-quality waveform. FiO2=fraction of inspired oxygen. PaO2=partial pressure of arterial oxygen. SpO2=pulse-oximetric oxygen saturation. *Alternatively, assessment can be made using arterial blood gas.
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