Bioamplifier

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. Efforts to amplify biosignals started with the development of electrocardiography. In 1887, Augustus Waller, a British physiologist, successfully measured the electrocardiograph of his dog using two buckets of saline, in which he submerged each of the front and the hind paws. A few months later, Waller successfully recorded the first human electrocardiography using the capillary electrometer. However, at the time of invention, Waller did not envision that electrocardiography would be used extensively in healthcare. The electrocardiograph was impractical to use until Willem Einthoven, a Dutch physiologist, innovated the use of the string galvanometer for cardiac signal amplification. Significant improvements in amplifier technologies led to the usage of smaller electrodes that were more easily attached to body parts. In the 1920s, a way to electrically amplify the cardiac signals using vacuum tubes was introduced, which quickly replaced the string galvanometer that amplified the signal mechanically. Vacuum tubes have a larger impedance, so the amplification was more robust. Also, its relatively small size compared to the string galvanometer contributed the widespread use of the vacuum tubes. Furthermore, the large metal buckets were no longer needed, as much smaller metal-plate electrodes were introduced. By the 1930s, electrocardiograph devices could be carried to the patient's home for the purpose of bedside monitoring. With the emergence of electronic amplification, it was quickly discovered that many features of the electrocardiography were revealed with various electrode placement. Electrocardiography (ECG or EKG) records the electrical activity of the heart, across the surface of the thorax skin.