Pulse oximetry beyond oxygen saturation: Early waveform characteristics in sepsis patients with adverse outcomes - A...

Sepsis is a life-threatening disorder with an in-hospital mortality rate of 10-40 %. Identifying patients at risk for deterioration is critical in guiding clinical decisions for patients with infection at the emergency department (ED). While pulse oximetry is known for estimating oxygen saturation, we hypothesize that photoplethysmography (PPG) can reflect early cardiovascular changes in sepsis. This study explores the potential use of pulse oximetry - PPG as a tool for predicting clinical deterioration in patients with early sepsis.

We conducted a secondary analysis of prospectively obtained data from the Acutelines data-biobank, involving 576 patients with early sepsis at the ED. Clinical and demographic data, vital signs, laboratory values, and PPG waveforms were collected. Groups were determined by a composite endpoint of intensive care unit (ICU) admission and/or in-hospital mortality within 48 h. PPG features were calculated and differences between groups were analyzed.

Within our study cohort, 9.7 % of patients were admitted to the ICU and/or deceased within 48 h after ED arrival. During the first 20 min after ED arrival, patients who deteriorated showed lower systolic peak amplitude (SPA: 1218 vs. 1490 AU, p < 0.001), lower diastolic peak amplitude (DPA: 462 vs. 621 AU, p < 0.001), and shorter pulse intervals (PI: 0.540 vs. 0.609 s, p < 0.001) on PPG. Additionally, the APG b/a ratio was lower (-0.881 vs. -0.802, p < 0.001). In contrast, systolic blood pressure (SBP: 123 vs. 129 mmHg, p = 0.186), diastolic blood pressure (DBP: 78 vs. 76 mmHg, p = 0.400), mean arterial pressure (MAP: 88 vs. 95 mmHg, p = 0.111) did not differ between groups. Heart rate (HR: 111 vs. 99 bpm, p = 0.001) and PPG-derived PI were both significantly different and strongly correlated (ρ = -0.921), as both reflect the duration of one interbeat interval.

This study highlights the potential use of PPG as a valuable tool for detecting early cardiovascular changes in sepsis. These findings hold significance for developing novel tools that can facilitate early identification of patients at risk for deterioration, thereby improving clinical decisions and outcomes for ED patients with early sepsis.