JMIR Publications

ABSTRACT

Background:

Accurately assessing pain severity is essential for effective pain treatment and desirable patient outcomes. In clinical settings, pain intensity assessment relies on self-reporting methods, which are subjective to individuals and impractical for noncommunicative or critically ill patients. Previous studies have attempted to measure pain objectively using physiological responses to an external pain stimulus, assuming that the human subject is free of internal body pain. However, this approach does not reflect the situation in a clinical setting, where a patient subjected to an external pain stimulus may already be experiencing internal body pain.

Objective:

This study investigates whether an individual’s physiological response to an external pain stimulus is influenced by the presence of preexisting pain.

Methods:

We recruited 39 healthy subjects aged 22–37, including 23 females and 16 males. Physiological signals – Electrodermal Activity and Electromyography – were recorded while participants underwent a combination of preexisting heat pain and cold stimulus. Statistical analyses were performed to identify key features of physiological responses affected by varying levels of preexisting pain.

Results:

Our analysis confirmed the hypothesis that the body exhibits different physiological responses to an external pain stimulus when influenced by varying levels of preexisting pain. Distinct features of EDA and EMG signals, such as statistical metrics and distributional characteristics, were identified as markers of this variation.

Conclusions:

This study demonstrates that preexisting pain alters physiological responses to new pain stimuli, highlighting the need to account for preexisting pain when developing objective pain assessment methods in clinical settings.