In 1922, British researchers Crighton Bramwell and A.V. Hill published two papers about the blood pulse wave velocity after conducting a study on a living man and on an isolated artery.
To study the isolated artery, which was 6.84 cm long, Bramwell and Hill had to use mercury instead of blood to slow the pulse wave velocity enough to make it possible to measure the time it took the pulse wave to travel the length of the artery. The density of mercury is 3.58 higher than blood and decreases the pulse wave velocity accordingly [1].
With this experiment, the researchers proved that the pulse wave velocity was between four and five meters per second when the pressure was between 25 and 80 mmHg, but increased up to 18 m/s when the pressure raised to 200 mmHg. Bramwell and Hill concluded that “the transmission of the pulse-wave is a purely mechanical effect, its velocity depending on the extensibility of the vessels”.
In their research with a living person, they used hot-wired sphygmograms to analyze the pulse wave from two locations: near the aorta and on the radial arteries (near the wrist). By calculating the time it took from the pulse wave to travel the distance, they could confirm that the blood wave velocity on a living subject is in-line with the measurements they had earlier made with the isolated artery.
Based on their measurements, they stated that “The older the subject the more rigid are his arteries, and the higher the velocity of transmission of the pulse-wave.”. And in the summary, “The measurement of pulse-wave velocity affords direct objective evidence in the diagnosis of arterio-sclerosis and aneurysm.” [2].
During recent years the interest to develop wearable wrist-devices that estimate blood pressure based on pulse transit time (PTT) has increased dramatically. Now, 100 years later, it is a perfect time to appreciate the pioneering work on this topic done by Bramwell and Hill.
References:
1.The Velocity of the Pulse Wave in Man. J. Crighton Bramwell and A.V. Hill. Proceeding of the Royal Society, 1 April, 1922
2.Velocity of Transmission of the Pulse-Wave. J. Crighton Bramwell and A.V. Hill. The Lancet, May 6, 1922
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