An experimental analysis of discrimination of pulse transit time.

The present study attempted to determine if individuals could be trained to discriminate changes in their own pulse transit time, an indirect estimate of relative (systolic) blood pressure. A single-subject ABAB reversal-reinstatement design was used in an experimental analysis of the effects of feedback on pulse transit time discrimination in a normotensive and essential hypertensive subject. Subjects engaged a response button on a free-operant schedule each time they felt pulse transit time was momentarily below a predetermined mean. After baseline, visual feedback was provided contingent on correct responses (feedback) and incorrect responses (reversal). Procedures also assessed the role of respiration as a possible discriminative stimulus. For both subjects discrimination improved during feedback, showed disruption when the reversal was implemented, and subsequently improved during the second feedback phase. Respiration did not appear to have served as the discriminative stimulus. Results are discussed in terms of the need for refining procedures, especially to ensure generalization to no-feedback conditions, and the potential applications and importance of training of pulse transit time.