Stethoscope

The stethoscope is one the most basic instruments used in diagnosing health problems and treating patients. Stethoscope was invented in 1816 by the French physician Rene Theophile Hyacinthe Laënnec (1781-1826). Laënnec was a military surgeon during the Revolution and Napoleon era.

Stethoscopes are used to transmit the sounds from a patient to the ears of the practitioner. The sound waves from the patient are transmitted to the scope’s bell or diaphragm of the chest piece via direct contact with the patient. The sounds are then transmitted down the tubing of the scope and into the binaural earpieces and into the ear.

Eartips are the parts that fit into the user ear. They should fit snugly, sealing out ambient noise and helping the user to focus on auscultation.

Stethoscope tubing is designed to transfer acoustic sound waves channeled by the stethoscope’s diaphragm and bell to the practitioner during auscultation. The thickness of the tube is an important factor in enhancing the efficiency of sound transference. Thicker stethoscope tubing transfers sound waves more efficiently while minimizing acoustic interference from the ambient environment.

Stethoscopes are used primarily for assessing the subtleties of cardiac (heart) and pulmonary (lung) sounds and to determine the presence or absence of bowel sounds. An ideal stethoscope should be able to deliver to the ears, without important loss or distortion, all audible physiological phenomena. These sounds normally fall in the acoustic range of 60-600 cycles per second, with some unimportant components of mitral diastolic murmurs below 60 and a few pulmonary rhonchi and rales as high as 1,000 cycles.

With the recent advancement in electronic technology, the digital and electronic stethoscope is gaining popularity day-by-day. Electronic stethoscopes can provide better sound quality with variable amplification, minimize interference noise, and provide data for visualization and storage.
Stethoscope

Invention of device for measuring blood pressure

It was William Harvey in 1616, who first described a one way circulation of blood and correctly suggested the existence of capillaries.

In 1722, Stephen Hales, an English clergyman, was the first person to measure blood pressure albeit in a horse. In 1733, he published a paper on his experiments on opening an artery in a live horse inserting a brass pipe 1/6 of an inch in diameter and attaching a vertical glass tube to this pipe.

He then allowed blood from the horse to enter the tube, and found that the blood level rose to a height of 8 ft 3 in, He also noticed that the height of the blood column rose and fell by 2-4 in with each heartbeat.

Almost 150 years later Samuel Siegfried Karl Ritter von Basch of Bavaria invented a machine that could measure the blood pressure of a human being in a non-invasive manner. It using an inflatable rubber bag filled with water. The bag was pressed over the pulse pulsation ceased and the height of the mercury column attached to the rubber bag reflected the systolic pressure.

This was the forerunner of the device introduced by Italian physician Scipione Riva-Rocci in 1896, which proved to be a prototype of the more refined instrument of today. He invented a simple device – a rubber bag that went around the arm, which was then filled with air in order to block the circulation in the brachial artery and determine at what pressure the blood was passing through.

This, along with invention of the stethoscope of Rene Laennec, helped Russian scientist NS Korotkoff in 1905 to monitor the pulse whilst the blood pressure cuff was inflated, and hence the term ‘Korotkoff sounds’.

Rene Laennec, French physician constructed the first stethoscope from a stacked paper rolled into a solid cylinder.

Although there are modern digital electronic instruments that are similar and more convenient to use, the mercury manual manometers are still considered to be gold standard as they do not need to be calibrated.

In 1978, Croslin Michael invented computerized blood pressure and pulse measuring device. His invention was the most sophisticated of its type, depending on the motion of the blood to determine its findings.
Invention of device for measuring blood pressure