String galvanometer

Last updated
An early commercial ECG machine, built in 1911 by the Cambridge Scientific Instrument Company Willem Einthoven ECG.jpg
An early commercial ECG machine, built in 1911 by the Cambridge Scientific Instrument Company

A string galvanometer is a sensitive fast-responding measuring instrument that uses a single fine filament of wire suspended in a strong magnetic field to measure small currents. In use, a strong light source is used to illuminate the fine filament, and the optical system magnifies the movement of the filament allowing it to be observed or recorded by photography. The principle of the string galvanometer remained in use for electrocardiograms until the advent of electronic vacuum-tube amplifiers in the 1920s. [1]

Contents

History

Submarine cable telegraph systems of the late 19th century used a galvanometer to detect pulses of electric current, which could be observed and transcribed into a message. The speed at which pulses could be detected by the galvanometer was limited by its mechanical inertia, and by the inductance of the multi-turn coil used in the instrument. Clément Adair, a French engineer, replaced the coil with a much faster wire or "string" producing the first string galvanometer. [2]

For most telegraphic purposes it was sufficient to detect the existence of a pulse. In 1892 André Blondel described the dynamic properties of an instrument that could measure the wave shape of an electrical impulse, an oscillograph. [1]

Augustus Waller had discovered electrical activity from the heart and produced the first electrocardiogram in 1887. [3] But his equipment was slow. Physiologists worked to find a better instrument. In 1901, Willem Einthoven described the science background and potential utility of a string galvanometer, stating "Mr. Adair as already built an instrument with a wires stretched between poles of a magnet. It was a telegraph receiver." [4] Einthoven developed a sensitive form of string galvanomter that allowed photographic recording of the impulses associated with the heartbeat. He was a leader in applying the string galvanometer to physiology and medicine, leading to today's electrocardiography. [5] Einthoven was awarded the 1924 Nobel prize in Physiology or Medicine for his work. [6]

Schema of Einthoven galvanometer, with quartz filament marked a-a'- 1903 Einthoven's string galvanometer.jpg
Schema of Einthoven galvanometer, with quartz filament marked a-a'- 1903

Previous to the string galvanometer, scientists were using a machine called the capillary electrometer to measure the heart’s electrical activity, but this device was unable to produce results of a diagnostic level. [7] Willem Einthoven adapted the string galvanometer at Leiden University in the early 20th century, publishing the first registration of its use to record an electrocardiogram in a Festschrift book in 1902. The first human electrocardiogram was recorded in 1887; however, it was not until 1901 that a quantifiable result was obtained from the string galvanometer. [8] In 1908, the physicians Arthur MacNalty, M.D. Oxon, and Thomas Lewis teamed to become the first of their profession to apply electrocardiography in medical diagnosis.[ citation needed ]

Mechanics

Einthoven's galvanometer consisted of a silver-coated quartz filament of a few centimeters length (see picture on the right) and negligible mass that conducted the electrical currents from the heart. This filament was acted upon by powerful electromagnets positioned either side of it, which caused sideways displacement of the filament in proportion to the current carried due to the electromagnetic field. The movement in the filament was heavily magnified and projected through a thin slot onto a moving photographic plate. [9] [10]

The filament was originally made by drawing out a filament of glass from a crucible of molten glass. To produce a sufficiently thin and long filament an arrow was shot across the room so that it dragged the filament from the molten glass. The filament so produced was then coated with silver to provide the conductive pathway for the current. [11] By tightening or loosening the filament it is possible to very accurately regulate the sensitivity of the galvanometer. [9]

The original machine required water cooling for the powerful electromagnets, required 5 operators [12] and weighed some 600 lb. [10]

Procedure

Patients are seated with both arms and left leg in separate buckets of saline solution. These buckets act as electrodes to conduct the current from the skin's surface to the filament. The three points of electrode contact on these limbs produces what is known as Einthoven's triangle, a principle still used in modern-day ECG recording. [13]

Related Research Articles

The diagnostic tests in cardiology are methods of identifying heart conditions associated with healthy vs. unhealthy, pathologic heart function.

<span class="mw-page-title-main">Galvanometer</span> Instrument to measure electric current

A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely.

<span class="mw-page-title-main">Electrocardiography</span> Examination of the hearts electrical activity

Electrocardiography is the process of producing an electrocardiogram, a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including cardiac rhythm disturbances, inadequate coronary artery blood flow, and electrolyte disturbances.

<span class="mw-page-title-main">Mirror galvanometer</span> Type of ammeter

A mirror galvanometer is an ammeter that indicates it has sensed an electric current by deflecting a light beam with a mirror. The beam of light projected on a scale acts as a long massless pointer. In 1826, Johann Christian Poggendorff developed the mirror galvanometer for detecting electric currents. The apparatus is also known as a spot galvanometer after the spot of light produced in some models.

String or strings may refer to:

<span class="mw-page-title-main">Willem Einthoven</span> Dutch physiologist

Willem Einthoven was a Dutch medical doctor and physiologist. He invented the first practical electrocardiograph in 1895 and received the Nobel Prize in Physiology or Medicine in 1924 for it.

<span class="mw-page-title-main">Holter monitor</span> Portable device for cardiac monitoring

In medicine, a Holter monitor is a type of ambulatory electrocardiography device, a portable device for cardiac monitoring for at least 24 hours.

<span class="mw-page-title-main">Heart rate monitor</span> Personal monitoring device

A heart rate monitor (HRM) is a personal monitoring device that allows one to measure/display heart rate in real time or record the heart rate for later study. It is largely used to gather heart rate data while performing various types of physical exercise. Measuring electrical heart information is referred to as electrocardiography.

A flatline is an electrical time sequence measurement that shows no activity and therefore, when represented, shows a flat line instead of a moving one. It almost always refers to either a flatlined electrocardiogram, where the heart shows no electrical activity (asystole), or to a flat electroencephalogram, in which the brain shows no electrical activity. Both of these specific cases are involved in various definitions of death.

<span class="mw-page-title-main">Einthoven's triangle</span> Concept in electrocardiography

Einthoven's triangle is an imaginary formation of three limb leads in a triangle used in the electrocardiography, formed by the two shoulders and the pubis. The shape forms an inverted equilateral triangle with the heart at the center. It is named after Willem Einthoven, who theorized its existence.

<span class="mw-page-title-main">Augustus Desiré Waller</span> British physiologist

Augustus Desiré Waller FRS was a British physiologist and the son of Augustus Volney Waller. He was born in Paris, France.

<span class="mw-page-title-main">Fleming valve</span> Type of vacuum tube; early radio detector

The Fleming valve, also called the Fleming oscillation valve, was a thermionic valve or vacuum tube invented in 1904 by English physicist John Ambrose Fleming as a detector for early radio receivers used in electromagnetic wireless telegraphy. It was the first practical vacuum tube and the first thermionic diode, a vacuum tube whose purpose is to conduct current in one direction and block current flowing in the opposite direction. The thermionic diode was later widely used as a rectifier — a device that converts alternating current (AC) into direct current (DC) — in the power supplies of a wide range of electronic devices, until beginning to be replaced by the selenium rectifier in the early 1930s and almost completely replaced by the semiconductor diode in the 1960s. The Fleming valve was the forerunner of all vacuum tubes, which dominated electronics for 50 years. The IEEE has described it as "one of the most important developments in the history of electronics", and it is on the List of IEEE Milestones for electrical engineering.

<span class="mw-page-title-main">Right axis deviation</span> Medical condition

The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an electrocardiogram (ECG). Normally, this begins at the sinoatrial node ; from here the wave of depolarisation travels down to the apex of the heart. The hexaxial reference system can be used to visualise the directions in which the depolarisation wave may travel.

A Bioamplifier is an electrophysiological device, a variation of the instrumentation amplifier, used to gather and increase the signal integrity of physiologic electrical activity for output to various sources. It may be an independent unit, or integrated into the electrodes.

<span class="mw-page-title-main">Cardiac monitoring</span>

Cardiac monitoring generally refers to continuous or intermittent monitoring of heart activity to assess a patient's condition relative to their cardiac rhythm. Cardiac monitoring is usually carried out using electrocardiography, which is a noninvasive process that records the heart's electrical activity and displays it in an electrocardiogram. It is different from hemodynamic monitoring, which monitors the pressure and flow of blood within the cardiovascular system. The two may be performed simultaneously on critical heart patients. Cardiac monitoring for ambulatory patients is known as ambulatory electrocardiography and uses a small, wearable device, such as a Holter monitor, wireless ambulatory ECG, or an implantable loop recorder. Data from a cardiac monitor can be transmitted to a distant monitoring station in a process known as telemetry or biotelemetry.

<span class="mw-page-title-main">Human Research Facility Holter Monitor</span>

The Human Research Facility Holter Monitor (Holter) is a battery-powered, noninvasive electrocardiogram (ECG) device that accurately measures the heart rate of crew members over an extended period of time. ECG information is stored on a Portable Computer Memory Card International Adapter (PCMCIA) card and downlinked to Earth for analysis after monitoring is complete.

Wireless ambulatory electrocardiography (ECG) is a type of ambulatory electrocardiography with recording devices that use wireless technology, such as Bluetooth and smartphones, for at-home cardiac monitoring (monitoring of heart rhythms). These devices are generally recommended to people who have been previously diagnosed with arrhythmias and want to have them monitored, or for those who have suspected arrhythmias and need to be monitored over an extended period of time in order to be diagnosed.

Horatio Burt Williams was an American clinical electrophysiologist.

Bioelectromagnetic medicine deals with the phenomenon of resonance signaling and discusses how specific frequencies modulate cellular function to restore or maintain health. Such electromagnetic (EM) signals are then called "medical information" that is used in health informatics.

Alexander Filippovich Samoylov was a Russian physiologist and pioneer of electrophysiology and electrocardiography who applied techniques of using the ECG for diagnostic purposes. He served as a professor at Kazan University from 1903 until his death.

References

  1. 1 2 Robert Bud (ed), Instruments of Science: An Historical Encyclopdedia, Garland Publishing Inc., 1998, ISBN 0-8153-1561-9 page 259
  2. ↑ [Adair C. Sur un nouvel appareil enregistreur pour câbles sous-marins ("On a new recording device for submarine cables") C R Acad Sci (Paris) 1897; 124:1440-2.]
  3. ↑ [Waller AD. A demonstration on man of electromotive changes accompanying the heart's beat. J Physiol 1887; 8:229-34]
  4. ↑ [Einthoven W. Un nouveau galvanomètre. ("A New Galvanometer") Arch Neeri Sci Exactes Nat 1901; 6:625-33]
  5. ↑ [Cooper JK. Electrocardiography 100 years ago. New England J Med1987;215:461-3]
  6. ↑ Bowbrick & Borg (2006), p. 10.
  7. ↑ 'Einthoven's String GalvanometerThe First Electrocardiograph', Moises Rivera-Ruiz et al, Tex. Heart Inst. J. © 2008 by the Texas Heart Institute
  8. ↑ Bowbrick, S.; Borg, A.N. (2006). ECG Complete. Elsevier Limited. p. 2.
  9. 1 2 'Willem Einthoven and the Birth of Clinical Electrocardiography a Hundred Years Ago', S. Serge Barold, Cardiac Electrophysiology Review, Springer Netherlands January 2003
  10. 1 2 Einthoven (1901)
  11. ↑ A History of Electrocardiography pg 112-113
  12. ↑ NIH Archived 2008-05-14 at the Wayback Machine
  13. ↑ Bowbrick & Borg (2006), pp. 9–10.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.