evolution of patient monitors

Evolution of Patient Monitors

Controlled and accurate patient monitoring is critical in almost all aspects of patient care, from operating theatres and intensive care units to recovery rooms and out-patient care.

Patient monitoring has changed enormously over the last few decades. Not so long ago, a different monitor was needed to measure each and every individual vital sign. Nowadays, multiple parameters can be assessed by a single monitor, which may be portable or even handheld, and is probably connected to an integrated network. It is now also possible for wireless sensors to measure and transmit physiological data from a patient to a central control room for the purposes of monitoring and recording.

The following article summarizes the main milestones in the evolution of techniques for the monitoring of the human body; from early explorations into the importance of measuring vital signs to the introduction of state-of-the-art, integrated, multi-parameter measurement devices available for use by today's healthcare provider.

Evolutionary timescale

In 1625, an Italian physician by the name of Santorio became the first person to measure body temperature, using a spirit thermometer. It would be more than 80 years before attempts were made to record another of the vital signs, pulse rate.

In 1707, John Floyer, an English physician, created a special watch for measuring the pulse rate over a period of 60 seconds. He published his findings in "Physician's Pulse Watch", but was largely ignored for over one hundred years.

In 1847, the first successful measurement of human blood pressure was reported (techniques had been available for the measurement of blood pressure in animals since 1733 through a highly invasive technique that was inappropriate for clinical use). The method developed for humans used a U-shaped manometer tube connected to a brass pipe cannula directly into the artery. The manometer tube had an ivory float onto which was attached a rod with a quill which would sketch onto a rotating drum. Although a significant development, blood pressure could still only be measured by invasive means.

In 1852, Ludwig Traube, the son of a Jewish wine merchant, investigated pathophysiology of respiration and the regulation of the body temperature.

In 1855, the German physician Karl Vierordt used an inflatable cuff around the arm to constrict the artery to measure blood pressure non-invasively. This device is considered a forerunner of the modern sphygmomanometer, which was developed a few years later.

In 1881, the sphygmomanometer was invented by Samuel Siegfried Karl Ritter von Basch, consisting of a water-filled bag connected to a manometer. The manometer was used to determine the pressure required to obliterate the arterial pulse. Results from this technique were found to be consistent with the previous method of direct measurement of blood pressure by catheterization, confirming that von Basch's design would allow a non-invasive method to measure blood pressure.

In 1896, Scipione Riva-Rocci introduced the mercury sphygmomanometer, which was easy to use and gave reliable results. This device, the standard instrument for measuring blood pressure, led to many new developments in the management of hypertensive disease.

In 1901, Willem Einthoven invented a string galvanometer for recording electrical impulses deriving from the heart. Einthoven's device used a very thin filament of conductive wire passing between very strong electromagnets. When a current passed through the filament, the electromagnetic field would cause the string to move. A light shining on the string would cast a shadow on a moving roll of photographic paper, thus forming a continuous curve showing the movement of the string. This device allowed the electrical activity of the heart to be measured accurately for the first time despite the obstruction of flesh and bones. Einthoven published the first electrocardiogram recorded on a string galvanometer in 1902. He was awarded the Nobel Prize in 1924 for his discovery of the mechanism of the electrocardiograph

In 1905, Nikolai Korotkoff developed a non-invasive technique for the determination of systolic and diastolic blood pressure through the use of a sphygmomanometer and a stethoscope. The pulse-synchronous circulatory sounds hears through the stethoscope are still known as 'Korotkoff sounds', and this method remains the 'gold-standard' of blood-pressure measurement.

In 1905, Einthoven began transmitting electrocardiograms from the hospital to his laboratory 1.5 km away via telephone cable. The first telecardiogram was recorded from a healthy and vigorous man, and the tall R waves were attributed to his cycling from laboratory to hospital for the recording.

In 1915, the world's first hand-held, direct-illuminating ophthalmoscope developed by Dr. Francis Welch and William Noah Allyn (founders of WelchAllyn) was sold.

In 1990, computer-based patient monitors were first introduced into hospitals, and included monitors with database functions, report-generation systems, and monitors with decision-making capabilities.

In 1994, WelchAllyn introduced the first low-cost vital signs patient monitor, combining basic vital signs diagnostics in an easy-to-use, digital and affordable package.

In 2004, a system was developed for transmitting patients' self-reported outcomes using mobile phones or the internet. This allowed full remote and real-time monitoring of patients' vital signs for the first time, affording greater freedom to patients

In 2008, the first wireless patient-worn monitor launched, including ECG and SpO2, and ECG processing was introduced.

In 2009, GE Healthcare launched its CARESCAPE™ Monitor B850, allowing direct links between hospital networks, electronic medical records, diagnostic images, lab results and third-party devices with real-time patient monitoring data. This system allows streams of patient data to be transformed into meaningful and clinically accessible information to support fast and easy clinical decision making.

In 2009, GE Healthcare announced an initiative aimed to develop wireless medical monitoring systems, or body sensor networks (BSNs), which would replace the traditional tangle of bedside cables used to capture a patient's vital signs. The company is now developing BSNs, which consist of sensor devices that collect critical patient-specific information, including temperature, pulse-oximetry, blood glucose levels, electrocardiogram readings, blood pressure levels and respiratory function. This real-time patient information can be collected and transmitted to doctors and nurses to enable efficient patient monitoring from any location.

Developments in patient monitoring are occurring faster now than at any time since its earliest origins in the seventeenth century. It is thought that US demand for patient monitoring systems will grow 5.4 percent annually through 2010, bolstered by technological advances. Electrochemical blood glucose test strips, diabetic electrodes and sensors, and diabetic catheters are predicted to lead growth among accessories, while wireless multi-parameter monitors and stations are likely to pace gains in equipment sales.

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