[Influence of change in dental chair position on circulation kinetics. 1. Effects on rate x pressure product].

The rate x pressure product is a product of the systolic blood pressure and heart rate and is widely used in clinical medicine as an index of the cardiac oxygen supply-demand balance. Employing 20 healthy male subjects, we studied the changes in the rate x pressure product due to a body position change from the sitting position to the supine position in a dental chair. The following results were obtained: 1. The change from the sitting position caused a 10% decrease in the rate x pressure product, and this value did not return to the initial sitting position value even after 5 min in the supine position. 2. The heart rate tended to decrease due to the position change. 3. Immediately after the position change, the systolic blood pressure decreased significantly (p less than 0.05), but it tended to return to the initial value with the lapse of time. The lower rate x pressure product in the supine position suggests that the supine position is more advantageous than the sitting one in treatment of the elderly and patients with cardiovascular diseases from the viewpoint of the systemic cardiovascular kinetics.