The twentieth century saw physicians and pharmacologists seeking better drugs to alleviate pain. In 1929, the National Research Council launched a forty-year drive to develop an analgesic stronger than aspirin but without the addiction potential of narcotics. More than 500 compounds were developed, several of which appeared to induce analgesia in animals. How could these be tested in humans?
At Cornell University, physiologist James Hardy, neurologist Herbert Wolff, and researcher Helen Goodell used very precisely calibrated radiant heat stimuli directed to the foreheads or hands of trained experimental subjects. They asked the subjects to report each "just noticeable difference" in the intensity of pain experienced, and graphed their responses on the "dol" scale, in which one dol equals two just noticeable differences, or "jnds". Their method produced very elegant graphs showing the comparative effectiveness of various analgesics, and the physiologic responses associated with different intensities of pain.
Hardy, Wolff and Goodell emphasized the functioning of the sensory systems:
"[Our concept] holds a pain experience to be composed not only of pain sensation but of associated sensations and of emotional and affective states as well. . . Such a concept does not fail to take into account the fact that important bodily reactions to noxious stimulation, themselves entirely below the level of conscious activity, may contribute new sources of noxious stimulation and pain. Also, because of the intimate linkage of pain sensation with strong emotions, feelings, and behavior patterns, these may be dominant in the experience. However, since by definition the pain experience must include pain sensation, associated phenomena, although important, are given secondary consideration in this essay." (From: James D. Hardy et al. Pain Sensations and Reactions. New York: Hafner, 1967)
Henry Knowles Beecher (1904-1976)
"Thus emotion can block pain; that is common experience. It is difficult to understand how emotion can affect the basic pain apparatus than by affecting the reaction to the original sensation." Certainly psychological effects have great influence on subjective responses, not only pain but other responses as well. Every small boy has learned, knows, even though he does not consciously recognize the fact, that emotion can block the pain of a wound received during fighting but not perceived until the fight and the emotion have subsided." (From: Henry K. Beecher. Measurement of Subjective Responses: Quantitative Effects of Drugs. New York: Oxford University Press, 1959)
Beecher's research team at the Anesthesia Research Laboratory at Harvard and Raymond Houde's group at Memorial-Sloan-Kettering developed new methods of testing analgesics on clinical patients, in which each patient received different analgesics in sequence, serving "as his own control." This "crossover" method controlled for the subjective experience of each patient. Beecher asked each patient to report whether she experienced 50% relief of her pain, yes or no, while Houde and his associate, Ada Rogers, asked their subjects to quantify their pain on a scale of 1-4.
Raymond W. Houde describes how he began his research in the early 1950s:
"And in those days I had no help and I had my responsibilities in the Department of Medicine, so I made my own charts and everything. And they were mostly handmade charts and I'd have the patients keep them. And I learned to use, I developed a simple scale, and it was an ordinal scale primarily. They would note that severe pain was more than moderate pain, that's more than slight pain. . . and it was sort of quasi-quantitative, because we had no way of knowing how much slippage there is between the various categories. And we had no precise way of measuring it. I learned by this time that I wasn't going to depend upon the Wolff-Hardy-Goodell apparatus or anything else, because from my experience, it didn't add to what I knew. In fact, in my few experiments in that early time, I found that I got the same answer from just asking the patient, as I did by going through a long series of testing." (From the Oral History of Raymond W. Houde, 1995)
Pain Measurement Tools
Pain measurement in patients continues to depend on methods which can utilize, or control for, subjective experience. Here are some examples of pain measurement tools currently in use: