Effect of external cuff pressure on arterial compliance

Pressure is one of the most sensitive factors influencing the arterial wall compliance. Pulse transit time (PTT) is one simple way to assess arterial compliance changes. This study investigated the relationship between external cuff pressure and pulse transit time. The study was performed on 10 subjects with different cuff pressures (0, 10, 20 and 30 mmHg) on the lower arm, upper arm and whole arm (with two cuffs applied simultaneously on the lower arm and upper arm). The overall mean pulse transit time difference with the above different cuff pressures on the lower arm compared with that without cuff pressure were 3.3 ms, 6.9 ms, 10.1 ms. With the cuff on the upper arm, changes with increasing cuff pressure were greater, which were 3.7 ms, 8.5 ms and 13.1 ms. And for the whole arm, the changes were 5.6 ms, 11.6 ms and 18.0 ms, which were greater still. The mean PTT when the cuff pressure was applied to the whole arm was significantly larger (P<0.001) than the corresponding mean PTT when the cuff pressure was separately applied to the lower arm and upper arm. The mean PTT with the cuff on upper arm was also significantly larger than the corresponding mean PTT with the cuff on the lower arm, except with a cuff pressure of 10 mmHg. The sum of PTT changes with the cuff on the upper and the lower arm was significantly larger than that with the cuff on whole arm. A conclusion was made that when the external cuff pressure increased, arterial wall compliance increased, which was detected with increased pulse transit time.