Photoplethysmography (PPG) is a technique that permits noninvasive measurement of changes in the volume of tissues. A novel device uses PPG to assess changes in duodenal mucosal perfusion. When tested in septic piglets, data obtained using this device correlate with the blood lactate concentration and duodenal serosal microvascular blood flow as measured with a laser Doppler flowmeter. This new...

Metrics of heart rate variability (HRV) are widely used in medical diagnostics, physiological research, and biofeedback training (TaskForce, 1996; Wheat & Larkin, 2010). HRV metrics are typically based on non-invasive measurements of cardiac function using electrocardiography (ECG) or photoplethysmography (PPG). A specific point is identified in each cardiac cycle, and the inter-beat interval (...