MONTREAL--A new instrument for measuring pain intensity--the visual analogue thermometer (VAT)--developed to overcome some of the disadvantages of the conventional visual analogue scale (VAS)--has proved "valid, accurate, and clinically useful" in two studies, say Manon Choinière, PhD, of the Burn Centre, Hotel-Dieu Hospital of Montreal and the University of Montreal, and Rhonda Amsel, MSc, of the Department of Psychology, McGill University.
With the VAS, patients must make a mark along a 10-cm line that has "no pain" and "unbearable pain" as the two extremes. The scale is then scored by measuring the distance in millimeters from "no pain" to the patient's mark.
Dr. Choinière describes the potential disadvantages of this scale as follows: (1) It may be physically awkward to complete for burn patients who have difficulty holding a pen or for those with perceptual or motor problems; (2) it does not provide an immediate result since the line has to be measured; and (3) it may be difficult for some patients to understand.
The VAT, an adaptation of the VAS, was developed at the Burn Centre, Hotel-Dieu Hospital of Montreal. It does not require any writing or use of the hands by the patient.
The VAT consists of a rigid white cardboard strip with a horizontal black opening through which a red band can be moved from left to right using a tab on the back of the device.
The left and right extremities of the opening are labeled "no pain" (or "aucune douleur") and "unbearable pain" ("dou-leur insupportable"). The patient is told that the device works like a thermometer except that it is measuring pain intensity in millimeters rather than body temperature in degrees.
The patient or an assistant slowly moves the red band to a position indicating the patient's pain intensity. "The more intense the pain, the more the red band lengthens toward the limit of unbearable," Dr. Choinière explains. This can then be read as a numerical value by using the 10-cm ruler printed on the reverse side of the device.