Scientists created a pain measurement scale by burning the hands of women in labor
In the 1940s, a group of doctors at the University of Cornell set out to create a unit of pain intensity. Using the “dol” as a unit, the physicians created a 21-point quantitative scale, but through unusual means — testing pain reactions on medical students and women in labor between contractions. They did this by burning their subjects. Ow.
The “dol” never quite caught on as a unit of pain measurement, but the story of its development gives us a window into just how far people were willing to go back in the day, for the sake of knowledge.
The value of a dol
In 1940’s Studies on Pain: A new method for measuring pain threshold, researchers inflicted pain upon subjects using by applying heat to their foreheads for three seconds at a time. Only four subjects took place in the first study, but each subject took part in over 100 pain-inflicting experiments, with the intensity of pain increasing as researchers increased the heat in each experiment.
Harvey’s group had a noble goal: creating an objective measure of human pain. They devised a unit for the intensity of pain, which they named the dol, with the name coming from the Latin word for pain, dolor. Ideally, the measurement would be applicable regardless of the type of pain.
Hardy and colleagues refined measurements on the dol scaled to a 21 interval series in the paperDiscrimination of differences in intensity of a pain stimulus as a basis of a scale of pain intensity, with a single dol divided into two “just discernible changes in pain”.
Through thousands of measurements, researchers created a 0 to 10.5 dol scale, with the heat intensity necessary to register any pain above 10.5 dols deemed indiscernible by the subject. At 8 dols, a level often reached in the experiments, the device left second degree burns on the subject’s forehead. Needless to say, moving a grant application for this type of research through your local University’s Institutional Review Board would be extremely difficult in the 21st Century.
Does 4 dols = 2 dols + 2 dols?
Through the experiments, Hardy and colleagues made an arithmetic conclusion concerning the dol scale – one difficult to wrap the mind around. The study’s authors concluded that 8 dols of pain equaled four successive two dol experiences. This arithmetic aspect of the dol contrasted existing beliefs of the subjective nature of pain.
This controversial result of the study used data from 70 medical students who carried out the experiments on each other. Medical students made for an accessible and pliable study group, as Hardy also concluded that fatigue felt by the students (with students tending to stay awake for 30 hours straight) played no role in measures of pain intensity.
Burning women in between contractions
In the 1948 paper, Studies on Pain: Measurements of Pain Intensity in Childbirth, Hardy subjected 13 women to heat-radiated pain in between labor contractions, in order to use the dol scale to quantify the intensity of labor pains.
After marking each woman’s hand in four places, researchers subjected her to multiple heat pulses immediately after she experienced a contraction. Researchers tried to select some heat pulses just below the assumed pain level of the contraction and some above, with the hopes of pin-pointing where her latest contraction measured, in dols.
Researchers chose four places on each hand as the heat-initiated pain data had to be gathered quickly, before another contraction arrived. Four choices allowed the researchers an ability to attain multiple readings without allowing one area to become desensitized.
The researchers achieved a modicum of success in these experiments. One of the women in labor registered a contraction measured at 10.5 dols through administered heat, the maximum value for the dol scale. As the heat blistered her hand, the subject helped established a value of pain intensity encumbered during child birth — a pain that can meet or exceed the perceived human threshold for pain.
From these data points, Hardy quantified the pain experiences in the stages of labor in dols, with the first stage corresponding to 2 dols, a value of 10.5 dols reached as the child crowns, and pain subsiding from 3 dols to baseline in the two hours after birth.
Due to the inability of patients to separate the intensity of pain from the type of pain, and problems with the subjective experience of pain, the dol never found its way into common use. Physicians and nurse practitioners continue to use the less analytical scales that Hardy had set out to replace.
The original papers are available for free online, and make for fascinating reading. The authors did a spectacular job of explaining their motives, writing in an easy-to-understand style, and the authors often interject a large amount of personal opinion into the reactions of individual subjects. The reading is one part horrifying, one part jaw-dropping, and one part astonishing as it reveals how far research regulations have come in 70 years.