Abstract
Biomedical instrumentation is widely used in healthcare to monitor patients, diagnose and treat various pathologies, and advance biomedical engineering research. This chapter covers the measurement of biopotentials for diagnosis, including the electrocardiogram, electroencephalogram, electrocorticogram, electromyogram, electroneurogram, electrogastrogram, action potential, electroretinogram, and electro-oculogram. Pulse oximeters are also covered along with important therapeutic devices such as the artificial cardiac pacemaker, defibrillator, cochlear implant, lithotripsy, ventilator, anesthesia machine, heart-lung machine, infant incubator, electrosurgery, and tissue ablation. The chapter concludes by covering electrical safety, providing future subjects for research such as a blood glucose sensor, and a permanently implanted intracranial pressure sensor, and describing the major organizations that promote the field of Biomedical Instrumentation.
Top8.4. Historical Background And Literature Overview
Among the earliest electrical experiments were those by Luigi Galvani. In 1771, he discovered that the muscles of dead frogs’ legs twitched when struck by a spark.
Willem Einthoven invented the first practical electrocardiogram (ECG or EKG) in 1903. Einthoven placed the hands and feet of subjects in buckets of saline and used the string galvanometer to record the electrocardiogram (ECG) without electronics. The string galvanometer used a thin filament of conductive wire passing through strong electromagnets. When current passed through the wire, it would move the wire and its shadow from a light, which darkened moving photographic paper, which recorded the ECG.
In 1926, William Bovie developed the electrosurgical unit, which permitted surgery on vascular organs such as the brain, liver, and spleen. The development of the transistor and the computer enabled a flowering of the many advanced diagnostic and therapeutic devices we find in hospitals today.
Principles of Applied Biomedical Instrumentation, 3rd Edition, L.E. Geddes and L.E. Baker, John Wiley & Sons, New York, 1989, covers physiological events, many types of sensors, stimulators, radiant energy devices, ventilators, and anesthesia equipment.
The Encyclopedia of Medical Devices and Instrumentation, 2nd Edition, J.G. Webster, Ed., John Wiley & Sons, Hoboken NJ, 2006, is a six volume work of 300 articles that describes critical aspects of medical devices and instrumentation.
Medical Instrumentation Application and Design, 4th Edition, J.G. Webster Ed., John Wiley & Sons, Hoboken NJ, 2010 is a widely used text that encourages design of the above devices and instrumentation.
Key Terms in this Chapter
Heart-Lung Machine: Performs the functions of both the human heart and the lungs, allowing surgeons to suspend normal circulation to repair defects in the heart.
Electrosurgery: High frequency electric current applied to a scalpel to cut and coagulate tissue.
Electric Safety: Methods for minimizing electric shock to the body that might cause ventricular fibrillation.
Pulse Oximeter: A noninvasive method for monitoring the arterial oxygen saturation SO2 of a patient’s blood.
Lithotripsy: Focused ultrasound that disintegrates kidney stones.
Ablation: Destruction of tissue function – such as heating cancer to kill it.
Ventilator: A pump to force air into the lung to breathe for sedated patients.
Anesthesia Machines: Provide inhalational anesthetics as gases or volatile liquids and ventilate the lungs in sedated patients.
Cochlear Implant: For the totally deaf, electrodes placed within the cochlea to stimulate the auditory nerve and restore partial hearing.
Infusion Pump: A controlled pump for infusing fluids, nutrients, and drugs.
Infant Incubator: A newborn is placed in a box with controlled temperature and gas exchange.
Defibrillator: An electric stimulator that applies a large current pulse to cause all cardiac muscle to contract at the same time, to restore ventricular fibrillation to a normal pulse.
Hemodialysis: For kidney failure, blood is pumped past a semipermeable membrane to allow urea to diffuse to waste.
Artificial Cardiac Pacemaker: An implanted stimulator that electrically stimulates the heart to increase the heart rate.
Electrocardiographic Amplifier: An electronic amplifier that can increase the small 1 mV electrocardiogram (ECG) to about 1 V so it can be recorded and displayed.