Study of Influence of Preexisting Pain on the Body's Response to External Pain Stimuli

Abstract

The assessment of pain severity is essential for effective pain treatment. In clinical settings, pain intensity assessment relies on self-reporting methods, which are subjective to individuals and impractical for non-communicative or critically ill patients. In literature, there have been numerous attempts to objectively measure pain. In these studies, participants experience only one source of pain, which is not always the case in patients' medical conditions. In this study, our objective is to investigate the hypothesis that an individual's physiological response to external pain differs depending on experiencing preexisting pain. The underlying premise is that the body may exhibit different physiological responses to an external pain stimulus, depending on the intensity of the preexisting pain. To assess this hypothesis, we recruited 39 healthy subjects aged 22-37; among them, 23 were female, and 16 were male. Physiological signals - Electrodermal Activity and Electromyography - were recorded while participants underwent a combination of heat pain and cold stimuli. Through statistical analysis, we confirmed the hypothesis that the body exhibits different physiological responses to an external pain stimulus when influenced by preexisting pain. We identified key features of physiological signals (e.g., statistics and distributions) that significantly differ in response to new pain stimuli.