Ultra-Short-Term Analysis of Cardiovascular Interactions at Rest and During Orthostatic Stress Using Model-Free Mutual Information Rate

Study objectives: This study investigates the reliability of the Mutual Information Rate (MIR) for assessing cardiovascular interactions when computed from Ultra-Short-Term (UST) time series. While standard short.term (ST) analysis typically relies on 300-beat-long recordings, the increasing use of wearable devices has demonstrated the need for shorter recordings with reduced computational, storage and acquisition time requirements. Specifically, we examine whether shorter time series (down to 60 samples) can provide reliable insights into cardiovascular interactions and effectively discriminate among different physiological states, such as rest and postural stress, while offering the advantages of reduced real-time processing and storage requirements.