Last updated: Fri, Jun 30, 2017
Blood pressure, blood flow, heart rate, skin temperature, and skin conductance are all regulated through the autonomic nervous system and so are called autonomic measurements.
Blood flow has been studied in migraine patients. One study found that stress increased the blood flow velocity in migraine patients but not in normal controls.1 Both laser and ultrasound can be used with the Doppler principle that is used in traffic radar to measure the rate of blood flow.
Skin temperature is sensitive to stress, and it can be measured with thermistors in contact with the skin. Alternatively, infrared photographs of the skin can be used. Both low and high temperatures have been seen in people in acute pain. TMD patients have been found to have a higher temperature on the affected than on the unaffected side of the jaw.2
There is not a lot of research on the relations among blood pressure, pulse rate, and chronic pain. Some researchers have found that heart rate doesn't react very strongly to pain or other stresses in chronic pain patients. This is sometimes characterized as a lack of active coping
among these patients.3 One group devised a biofeedback training regimen for FMS patients with low heart rate reactivity. They reported that the training resulted in decreased depression and pain, as well as improved function.
Heart rate has been used in research as a correlate of acute pain. The authors of the chapter "Psychophysiological and Neuroimaging Measures in the Assessment of Patients with Chronic Pain" of the Handbook of Pain Assessment comment that, [h]owever, increases in tonic heart rate have been related more to subjective pain ratings than to objective characteristics of the nociceptive stimulus.
4 One study found a very low correlation between heart rate and pain among emergency room patients.5 Experimental studies have found that among hypertensives, more pain goes with lowered blood pressure, while among those with normal blood pressure, more pain goes with raised blood pressure.
Skin conductance goes up when sweat glands are activated by the autonomic nervous system in response to stress. Acute pain leads to increases in both heart rate and skin conductance. One experiment showed that skin conductance increased in patients who were exposed to words related to their own pain conditions.6