Enhancing sensitivity to facial expression of pain

Clinicians have long appreciated the information communicated by a patient's facial expression. Advances in the measurement of facial movements, using the Facial Action Coding System (FACS) have allowed for identification of a universal expression of pain, which is primarily encoded in four facial movements. While the FACS provides a rigorous assessment of facial expression, the time required to learn the system and to analyze the facial expression by use of slow motion video recording, makes its use impractical in the clinical setting. The purpose of this research was to examine whether exposure to a brief training procedure, based on orienting subjects to the four facial movements, would increase sensitivity to pain communicated by facial expression. Seventy-five occupational and physical therapy student volunteers were randomly assigned to training or control groups. The trained group was exposed to a 30-min training session. Both groups were then asked to rate a videotape of patients undergoing assessment of a painful shoulder and rate the amount of discomfort the patients appeared to be experiencing. Analyses indicated that the trained group was significantly more sensitive to subtle facial movements associated with low levels of pain. Relative to the patients' ratings, there was a tendency for raters to underestimate pain particularly when these were at a high level. The findings lend hope to the feasibility of developing a tool which would be clinically useful though this may be more difficult for observers judging more complex facial expressions associated with high levels of pain.