Vital signs are vital: Sphygmology
There is much more to checking a pulse than noting its presence or absence.
The following is one in a series of columns by guest authors illustrating the importance of vital signs to the practice of hospital medicine.
I remember well my first attempts to find the dorsalis pedis pulse and how hilarious it must have looked. Frantically pushing on soft and bony landmarks, as if I were giving some sort of half-hearted massage, I began to think that perhaps I should just say that I felt it, despite my sweat-browed appearance making it obvious that I had not. It wasn't until much later that I realized there was much more to “checking” a pulse than noting its mere presence or absence.
It would do us well to venture into the evolution of this rich source of visceral information, so we can keep a finger on the “pulse” of our own physical examination skills.
Nearly 2,500 years ago, the ancient Chinese studied the arterial pulse extensively. Believing that the pulse was based upon the various interactions between Yin (disease) and Yang (health), they used only 4 main varieties of pulse beats (superficial, deep, slow and quick) to determine the state of disease. Both wrists were used and examinations of any other palpable pulse were prohibited out of respect for the dignity of women.
In ancient Egyptian medicine, it was believed that there were two vascular systems: veins that carried digestive products to the body and arteries that carried pneuma (air) from the lungs to other organs. The word “artery” originates from the Greek language, in which the word is derived from the word for air. The Greek physician Herophilus (335-280 BC) and his contemporary Erasistratus (304-250 BC), expounded on this idea with the observation that veins contain blood and arteries contain air. They believed that the dilation of the arteries was a passive expansion caused by the movement of pneuma.
Herophilus is also notable as the first to measure pulse rate. He did so by creating the clepsydra, a Greek water clock. This was a massive piece of metal and water that he had toted around, undoubtedly by some medical student, on his rounds to measure the pulse of his patients.
Moving onto more sophisticated times, Galen (129-200) astoundingly described 27 characteristics of a single beat of pulse and was largely credited as the first person to use this knowledge in the diagnosis and prognosis of disease states. More than a century later, John Floyer (1649-1734) devised what is known as the first pulse watch. For this he is credited with being the first physician to count the pulse as we do today, per minute. In 1847, Carl Ludwig invented the Kymograph, a device which closely resembles a tool for medieval torture. Yet it was an amazing advance that enabled the physician to record numerous hemodynamic variables, allowing for further research into the cardiovascular system.
In 1833, a young pathologist in Britain, Sir Dominic John Corrigan, described an abrupt distension and collapse of the carotid arteries and its correlation to the patient's aortic insufficiency. From that time forward, this physical sign became known as “Corrigan's pulse.”
However, the more commonplace eponym for this characteristic is “Watson's water hammer pulse,” coined in 1844 by Sir Thomas Watson. Dr. Watson, among other notable accomplishments, was the president of the Royal College of Physicians from 1862-1866. Yet his name will go down in history for his astute observation that in patients with aortic insufficiency, the distinctly palpable pulse felt similar to the water hammer toy popular at the time. This Victorian toy was essentially a tube half-filled with fluid, the remainder being a vacuum. Children would invert and reinvert the tube, and each time, the impact of the fluid at the end would sound like a hammer blow.
Around the same time in Germany, Heinrich Irenaeus Quincke was born. After studying under the great Rudolf Virchow, Heinrich made some great contributions to medicine, including the introduction of the lumbar puncture. His contribution to the world of cardiovascular nomenclature also came from an aortic insufficiency physical sign. After he noted that the nails exhibited a pulsatile blanching and flushing and that this correlated to the patient's aortic insufficiency, “Quincke's sign” was born.
There must have been a lot of people running around 19th-century Europe with aortic insufficiency, because our next eponymous pulse is also in this category. During systole of patients with dramatically increased stroke volume, the uvula can pulsate or bob. This was recognized by another astute German clinician by the name of Friedrich von Müller, forever attaching his name to “Müller's sign.”
The physical investigation that was involved in connecting these signs with their underlying disease is hard to imagine without the technology we have today. Yet these clinicians were able to deduce from what they knew of physiology and its relation to what they saw on the outside. These realizations must have come from hours of experience at the bedside of patients.
However, connecting physical signs with an underlying disease that is truly emergent takes the detective prize. Later in the 20th century, an American cardiac surgeon pioneer, Claude Beck, working at Case Western Reserve University, made the connection between the combination of muffled heart sounds, distended neck veins and low arterial blood pressure. He concluded that this was the triad of signs for an acute cardiac tamponade. For his observations, this combination was named “Beck's triad.” Of course, he had the distinct advantage of being able to cut open the patient's chest and see firsthand how this triad correlated to the problem.
These are just a few of the eponymous signs relating to the cardiovascular system, deduced by brilliant clinicians who had only their hands and a pulsatile vascular system to diagnose visceral diseases. It's a reminder that physical examination is a powerful tool that is often underused due to technology today.