Non-Invasive Objective Markers to Measure Pain: A Direction to Develop a Pain Device - A Narrative Review.

Objective: To review the literature regarding non-invasive objective measurements of pain. Measuring pain is of uttermost importance, but it can be an inconvenient task, especially in terms of the interpretation of patient's information. Reiterating, there is no "standard" that provides the physician with a method to objectively quantify this problem of patient's pain. For assessing the pain, physician relies solely on unidimensional assessment tools or questionnaire-based pain assessment. Although pain is a subjective experience of the patient, but there is a need to measure pain sometimes in the individuals who cannot communicate their quality and severity of pain. Material and Methods: The articles from PubMed and Google Scholar without any year and age limit were searched in the current narrative review. A total of 16 markers were searched and their relation to pain was studied. Results: Studies have shown that these markers change in relation to pain and it can be considered a valuable tool for pain measurement but there are multiple factors like psychological and emotional factors which affect these markers. Conclusion: There is lack of evidence to show which marker can be used for measuring pain accurately. This narrative review is an attempt to look into the various pain-related markers that can be used and it calls for further studies including clinical trials with different diseases and taking into accounts different factors affecting pain to give an accurate measurement of pain.