STUDIES ON PAIN: MEASUREMENTS OF PAIN INTENSITY IN CHILDBIRTH 1

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Abstract
Measurements of pain intensity were made on 13 patients during 1st, 2d and 4th stages of labor without analgesia. The measurements were made by comparison of labor pains with a pain of standard intensity produced by a 3-sec. exposure to thermal radiation on the dorsal surface of the hand. The pain evoked on the hand had been previously standardized into 10.5 units of painfulness (10.5 dols) between the threshold pain and the most intense pain which can be experienced (ceiling pain). The intensity of the pain in the 1st stage of labor was roughly proportional to the extent of cervical dilatation and inversely proportional to the duration of the interval between uterine contractions. Pain intensity can be estimated approx. by the formula: Dols = 10.5 - 1.5 x contraction interval in minutes. The duration of pain was 15% of the contraction time for weak contractions characteristic of early labor, and 95% of contraction time at the beginning of the 2d stage of labor. The pain threshold was measured in the interval between contractions in the 1st, 2d and 4th stages of labor. It was within the normal range for all the patients who had received no analgesia or anesthesia. The intensity of the pain experienced by the patient could not always be evaluated on the basis of her reaction, nor correlated with her apparent distress. Distinguishing between the intensity of the pain perceived by the patient and the patient''s reaction has been made possible by measurements of pain intensity and pain thresholds.