Assessing Lung Function Using Peripheral O2 Saturation in Suspected Sepsis

Sepsis or septicaemia
Sepsis or septicaemia
Can peripheral oxygen saturation levels be used instead of arterial blood gas analysis to calculate SOFA scores in patients with suspected sepsis?

Peripheral oxygen saturation measurement can be used to assess respiratory function in the Sequential Organ Failure Assessment (SOFA) respiratory score and the Sepsis-3 criteria in most infected patients, according to a cohort study published in Critical Care Medicine.

Sepsis is a major cause of death in hospitals. The Sepsis-3 criteria developed in 2016 is based on the SOFA score, which was developed for intensive care units and requires arterial blood gas analysis to assess respiratory function. However, more than half of patients with sepsis are admitted to other hospital wards where the ability to assess full SOFA is limited.

Although not included in either the SOFA score or Sepsis-3, measurement of peripheral oxygen saturation represents a noninvasive alternative to using arterial blood gas analysis to assess respiratory function in these scoring rubrics. The current study sought to assess the viability of this alternative.

In the study, researchers assessed the association between mortality and patients’ worst peripheral oxygen saturation during onset of suspected infection. Data was prospectively collected from hospital admissions records from a main cohort of 19,396 episodes and emergency department visits from 4 external validation cohorts of 10,586 episodes.

The researchers found that peripheral oxygen saturation levels of 96% to 95% were not significantly associated with increased mortality in the main or pooled validation cohorts. However, at a peripheral oxygen saturation of 94%, the adjusted odds ratio of death was 1.56 in the main cohort and 1.36 in the pooled validation cohorts and increased gradually below this level. Thus, respiratory assessment using peripheral oxygen saturation, where 94% to 91% generate 1 SOFA point and less than 91% to generated 2 SOFA points, improved the discrimination of the SOFA score (P <.001). Although the clinical impact was minor, peripheral oxygen saturation/fraction of inspired oxygen (FiO2) ratio had slightly better predictive performance compared with peripheral oxygen saturation alone.

“This has important implications primarily for emergency practice, rapid response teams, surveillance, research, and resource-limited settings,” concluded the authors.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 


Valik JK, Mellhammar L, Sundén-Cullberg J, et al. Peripheral oxygen saturation facilitates assessment of respiratory dysfunction in the sequential organ failure assessment score with implications for the sepsis-3 criteria. Crit Care Med. Published online August 18, 2021. doi: 10.1097/CCM.0000000000005318