Physiological Measures of Acute and Chronic Pain within Different Subject Groups: A Systematic Review

Table 4

Pain assessment results per measurement method.

Method		Subjects	Able pain measure	Consistent across studies	Limitations
Electroencephalogram (EEG)		Neonates, infants, CPPs, ICU patients	Yes	Moderate	Influenced by opioids, not consistently found in neonates
Cardiovascular measures	Heart rate	Neonates, infants, TBI patients, ICU/OR patients, CPPs, people with SID, healthy adults	Doubtful	No	Variable results among brain injured patients, reduced reaction in CPPs, no reaction in SID
	Heart rate variability	Neonates, infants, ICU/OR patients, healthy adults	Yes	Moderate	Inconsistent among infants in the first year of life
	Body temperature	Neonates, infants, healthy adults	Yes	Moderate	Inconsistent among healthy adults
	Blood pressure	Neonates, infants, TBI patients, OR patients, healthy adults	Doubtful	No	Blood pressure responded inconsistently to pain
Respiratory measures	Respiratory rate	Neonates, infants, TBI patients, people with SID, healthy adults	Yes	Yes	Respiratory ‘irregularities’ were not related to acute pain in persons with SID
	Respiratory analysis	Neonates, infants, TBI patients	Yes	Yes	Oxygen saturation was not favored for pain in neonates
Muscular measures	Muscle tension	Infants, ICU/OR patients, healthy adults	Yes	Yes	In healthy adults muscle tension response was only found with intense and prolonged pain
	Electromyogram	CPPs, healthy adults	Yes	Yes	Few studies
Electrodermal activity		TBI patients, OR patients, healthy adults	Doubtful	No	Only consistently found in healthy adults
Pupillometry		Infants, OR patients, CPPs, healthy adults	Yes	Yes	Few studies
Brain scan	MRI	CPPs, healthy adults	Yes	Yes	Different studies focused on different areas
	NIRS	Neonates, infants	No	Yes	Presence of pain on a cortical level was not found
	CBFV	Infants, CPPs, OR patients, people with SID	Yes	Yes	Few studies
	SPECT	Infants, CPPs	Yes	No	Activity varied greatly across studies
Hormonal analysis		Neonates, CPPs	Yes	Yes	Few studies
Genetics		CPPs, healthy adults	Yes	Yes	Not yet validated in large human cohorts
Automatic facial recognition		CPPs	Doubtful	Yes	Influenced by gender, age, ethnicity, movement, and lighting

Note. CPPs = chronic pain patients, ICU = intensive care unit, OR = operating room, TBI = traumatic brain injury, SID = severe intellectual disability, MRI = magnetic resonance imaging, NIRS = near-infrared spectroscopy, CBFL = cerebral blood flow velocity, PET = positron emission tomography, and SPECT = single-photon emission computer tomography. [2, 10–37].