What is Biomedical engineering? It refers to the engineering that is involved in the design, manufacture and use of all such tools and instruments that the medical science use today for a host of diagnostic and therapeutic purposes. Given thus, the medical instruments of such a nature are called as biomedical instruments. Today, the use and necessity of such medical instruments or gadgets has become so pervasive in our life that without their being around us or beyond our access, it is quite possible that many a diseases or disorders that afflict our body could go undetected until it gets too long to remedy them off! Surely, these medical instruments constitute our alter-ego today given the fact that today’s fast paced life can throw our life and body out of gear more often than ever before and these medical instruments and tools invariably come handy to us especially at a time when they are required the most.

Depending upon their investigative use and the kind of diagnostic analysis of the body, they are being employed at; these medical instruments can be broadly classified into the following 3 categories:

1. Measuring instruments.
2. Imaging or viewing instruments.
3. Therapeutic instruments.

Measuring Instruments

There are following types of measuring instruments that the medical science uses today:

Clinical Thermometer: Commonly called as Doctor or Medical thermometer and is used for measuring the body temperature. It is calibrated from 94 degree Fahrenheit to 108 degree F and in terms of centigrade scale; it is calibrated from 35 degree C to 42 degree C. It is thus calibrated on such scales so as to contain in the normal body temperature of human beings that lies at and between 98.4-98.6 F or simply at 37 degree C. It was discovered by Sanctorius.

ECG (Electrocardiograph): An instrument used to measure the electrical activity of the heart muscles. The simple ECG monitor is called as cardioscope. It was invented by W.Einthoven. The instrument while measuring the electrical signals of the heart muscles amplify them that are then projected on a CRO (cathode ray oscilloscope) or on a graph paper that is what constitute a person’s electrocardiogram. An electrocardiogram serves a useful indicator of one’s heart health in the sense of determining the strength of heart muscles, its beating rate, so called rhythm of the heart beat or for that matter, disorders of the coronary artery etc.

EMG (Electromyograph): An instrument used for measuring the electrical activity of the muscle fibers as they contract and as such serves a useful purpose of detecting any nerve damage or the conditions of muscular dystrophy etc.

EEG (Electroencephalograph): An instrument used for determining the condition and the working of human brain besides, determining any sleep disorders or the effect of the drugs on the brain or CNS. It makes use of

some electrodes that are placed on the scalp that perceive the electrical signals of the nerve fibers and conduct them back after amplifying them onto a CRO that gives the EEG of a person’s brain.  Infact, this instrument determines the electrical activity of the brain in the form of waves what are called as brain waves. In a normal working brain, there are 4 types of brain waves that are being recorded through EEG. These are: Delta waves, Theta waves , Alpha waves, Beta waves

Autoanalyzer: It is a computer controlled device that is used for simultaneously measuring the presence of various biochemical substances in the blood say, for example, Urea, Cholesterol, Glucose and Bilirubin etc. The volume, temperature and timings of various samples introduced by micropipette are then supervised by a digital microprocessor.  

Polygraph: Commonly called as lie-detecting machine. It is compact and really portable devices that uses various physiological parameters of the body and perceive their changes rather than doing anything towards measuring them accurately. These parameters may include rate and depth of breathing, heart beat, conduction of impulse through skin and finger tips including the functioning of the brain by EEG and EOG (Electro-ocular graph) etc.

Sphygmomanometer: Commonly called as BP-apparatus and is used for measuring the blood pressure. The B.P of a person is usually measured from the Brachial artery of the left arm. The normal BP of an adult is 120/80 that measures the systolic and diastolic pressure respectively. In old age, this value may shoot up to about 160/95.

Stethoscope or phonograph: Invented by Rene Laennec and is an instrument that is used for hearing the amplified sounds (natural) of the body.

Imaging or viewing instruments

A class of medical instruments that are used for viewing and taking the picture of internal organs of the body so as to diagnose about the real health of a particular internal organ or part of the body or for that matter, diagnosing some other disorders in any of the internal organ of the body. They may be of the following types:

X-Ray Machine (Radiography): X-rays, a class of electromagnetic waves, discovered by W.Roentgen in the year 1898. X-rays being of shorter wavelength, even shorter than that of the UV rays can penetrate deep into the body tissues and thereby cast a shadow on the X-ray film to diagnose a particular defect or deformity in the body tissue. X-rays are mainly used for detecting bone disorders or fracture in them as the X-rays can enable us to differentiate between the harder and the softer tissues of the body. In medical parlance, the use of X-rays for diagnostic purposes is called as Radiography. For a better contrast of the X-ray images, Barium dye in gut and Iodine dye in Angiography are often used in radiography.

Angiography: It refers to taking pictures of a whole network of blood vessels in the body that include arteries, veins and blood capillaries for the purposes of detecting any blockage in them. As such, angiography can be performed for the blood vessels of the heart, brain or any other body organ for detecting any abnormality or blockage in them. Sometimes, another version of angiography is used what we call as digital subtraction angiography. In this technique, the angiography of the affected organ is done with or without the help of an opaque dye that is being injected into the blood. The angiograph thus obtained without the use of an opaque dye is then digitally subtracted with the help of a computer from the one that has been obtained using a dye. This gives a clear cut picture of the blood vessels and simultaneously, also indicates the degree of blockage developed due to a clot or some how, through cholesterol deposition.

Noted that once a clot has been detected, the same is then dissolved by injecting a drug obtained from a bacterium called as Streptokinase, also called as tPA that refers to (tissue plasminogen activator). The tPA generates an active enzyme called as plasmin that then degenerates or degrades the fibrin network of the clot…

CT-Scan (Computed Tomography): This technique was invented by Godfrey Hounsfield and earlier used to be called as CAT scanning (Computed Axial Tomography). This instrument makes the use of X-rays and with the help of a computer, produces a 3D image of the affected organ. The X-ray beam can be moved by 360 degree and sections from any axis can be visualized. Unlike simple radiography, there is no superimposition in CT scan so far as the images are concerned.

Endoscopy: A diagnostic technique used for studying the mucosa epithelium of the hollow or tubular organs of the body. This technique is based on the optic fibre technology. Depending upon the type of the internal organ being viewed or investigated, the endoscopy may be of the following types:

Bronchoscope: for studying the respiratory tract such as Bronchi and Bronchioles.

Gastroscope: for studying the stomach.

Laparoscope: for studying the female reproductive tract or system. The endoscope as an instrument makes use of various cables, of which one is meant for a light source and others for micro instruments for surgery as well as for collecting samples of the tissues.

Ultrasound (Sonography): A non-invasive diagnostic technique based on the phenomenon of piezoelectric effect. The lead zirconate crystals when subjected to high voltage, they undergo vibration and produce what we call as ultrasonic sound. This sound measuring 1-15 MHz in frequency is thus beamed into the body with the help of a transducer and its echo is recorded for scanning the body parts. The aqueous gel is applied between the skin and the head of a transducer to ensure air-free path to the sound to hit at the target organ. The echo thus, generates is converted into the electrical signals which are displayed on a CRO (Cathode ray oscilloscope). Noted that the technique of sonography or ultrasound does not make the use of any radiation source therefore, it is ideal and safe for testing or determining the position of the foetus in the womb and hence, is also suitable for detecting any abnormality in the developing baby or even of the mother’s reproductive system. The ultrasonic waves are also used for detecting and diagnosing heart ailments under the procedure of Echocardiography.

MRI (Magnetic resonance imaging): A diagnostic technique exactly based on NMRI that refers to Nuclear Magnetic resonance Imaging, discovered by Bloch and Purcell. This technique makes use of protons or hydrogen atoms that act as miniature magnets. A massive and cylindrical magnetic field is created using liquid helium that later generates resonance in hydrogen atoms. Since, the most abundant source of hydrogen atoms is water so this instrument can easily differentiate between water rich and water poor tissue. Based on this property, MRI is thus, prominently used for imaging brain and spinal cord as it will not form the images of the vertebrae or cranial bones because, both are being water poor tissue. Given thus, it can easily detect brain tumors or any nerve abnormalities as such. At the same time, it is also used for detecting cancer, haemorrhage, myocardial infarction, lesions of Multiple sclerosis, slipped disc, joint disorders or spinal cord damage etc.

MET (Magnetic Encephalographic technique): Like EEG, it also detects nerve impulses, but unlike EEG, it can detect weaker impulses also. MET uses SQUID that refers to super conducting quantum interference device for studying such impulses.

Echocardiograph:  It uses ultrasonic sound for imaging various parts of the heart. The electric signals received from the heart are amplified and viewed on CRO.

PET (Positron emitting tomography): PET makes the use of special radio-isotopes that are accelerated in a Cyclotron. The special radio-isotopes being used are Carbon-Eleven and Nitrogen-Thirteen isotopes that after being incorporated into glucose or amino acids are injected into the body. Once inside the body, these radio-isotopes emit positron and generate gamma radiations which are subsequently, detected by special devices and thus, help in imaging. The amount of glucose or amino-acid consumed is proportionate to the metabolic activity of the tissue. The organ which is metabolically more active will produce more gamma radiations and hence, produces more flashes. This instrument gives a qualitative and quantitative analysis of the tissue. In brain- image, the more lighted areas can be differentiated from the less lighter or dark portions. The color processing in the neocortex part of the cerebrum has been studies extensively by this technique. At the same time, this technique is also used for studying the nervous disorders of the nature of Schizophrenia, Epilepsy, Parkinson’s disease and severe cases of drug addiction etc…

Therapeutic Instruments

The medical science knows the following kinds of therapeutic instruments today:

LASER, Pace maker,Heart valve, Vascular graft, CABG (Coronary artery bypass grafting),Intra-aortic balloon pump,Angioplasty,Defibrillator,Haemodialyser,Heart lung machine,Artificial limbs,Hearing Aids,Denture and Intra-ocular lens etc… Let’s discuss their therapeutic use one by one.

LASER: LASER is an acronym for Light Amplification by Stimulated Emission of Radiations is essentially a high energy light called as photon beams carrying different wavelengths. In short, Laser beams are being monochromatic so as to increase their intensity. Laser can be of different types such as Argon laser carrying medium wavelength, carbon dioxide laser or neon laser etc. Argon laser being visible are generally employed for eye surgery. As the laser beams are known to be monochromatic in nature therefore, they are noted for having least deviation. Owing to this property, they are conveniently used for hitting at a specific target organ without harming the neighboring tissue.

Pace maker: Offering a fresh lease of life especially to those in which the natural pace maker of the heart has been dysfunctional or mal functional somehow such that there is nothing in place to set in the pace or rhythmic beat of the heart. In such people, what we call as artificial pace-makers have come handy. Artificial pace-maker was invented by Chardeck and appears as a mini-electronic device that is surgically placed or implanted below the collar bone in the chest muscles of such heart patients who typically exhibit some of the following types of symptoms:

?Their heart beat is irregular or arrhythmic,

? The Ventricles fail to receive impulses from the atria (Upper chambers of the heart),

? The atria and ventricles do not show a simultaneous contraction, but contract independently thereby, loosing synchronicity.

?The atrial impulse suddenly fails to be transmitted to the ventricles, a condition medically known as ventricular escape or Adam’s syndrome. The people having any of the above heart condition are recommended to go in for an artificial pacemaker. Structurally, it is a mini device that consists of two components called as a PULSE generator that remains fitted with a lithium-halide battery whereas, the second component of the device is called as electrode. The electrode is in the form of a fine spring that remains ensheathed in a biocompatible material. The tip of this electrode is inserted into the wall of the right ventricle through precaval vein. The lithium halide battery of this device could last for as long as up to 10 years.

Noted that since the artificial pacemakers come with lithium halide battery, the one that is being used in cellular phones as well. Hence, the pacemakers are strongly disturbed by cellular phones or otherwise, by any electro-magnetic device as such!

Heart valves: In rheumatic heart disease which is basically, an auto-immune disorder in which the self formed antibodies damage the heart valves. Hence, a need for having the artificial heart valves generally comes in such people. There are currently two types of artificial heart valves that are being used in the medical science:

?Tissue valves: They are either taken from cadaver (dead body) or from Pig or sometimes, may be prepared from the pericardium of the animals. However, the only defect and problem with these kinds of valves is their calcification for which reason, they are to be replaced from time to time.

?Mechanical valves: They are generally prepared from metal alloys or ceramics. In such valves, when the blood passes through the heart, the platelets get ruptured thereby, causing the problem of blood clotting. Such persons are therefore, oftenly prescribed anti-coagulants that are required to be taken by them almost regularly and probably, as long as they live.

Vascular Grafts: The need for vascular grafts arises especially in those people who are the sufferers of what we call as CAD; most importantly, atherosclerosis and aneurysm. While the former refers to a condition of constricted heart blood vessels due to the deposition of cholesterol and hence, narrowing down the lumen of the blood vessels that consequently becomes a cause of severely high blood pressure. Whereas, the latter refers to other way round condition in which there is an excessive dilation of the blood vessels and thus, a very low BP. In either of the conditions however, the damage to the blood vessels could occur which can be remedied off by replacing the damaged blood vessels by artificial vascular grafts which are thus also called as artificial arteries. These artificial grafts are generally made of a synthetic polymer called as Dacron or Teflon and are available in ready-made form of different diameters, but are unfortunately, not suitable for replacing the smaller arteries of diameter less than 6 micro meter.

CABG (Coronary artery bypass grafting): This is in common parlance, called as by pass heart surgery which is required to be performed when a blood vessel supplying blood to the heart is blocked either due to deposition of cholesterol or due to the formation of a blood clot what we call as thrombus. In order to set of the said problem, a by pass surgery is the only solution in which a by-pass artery is implanted to maintain the blood supply to that very portion of the heart. Noted that for this purpose, it is either the Saphenous vein from the leg or a mammary artery is being used as a graft, but most commonly has been the saphenous vein from the leg.

Intra-aortic balloon pump: This therapeutic instrument is used when the pumping action of the heart ventricles becomes extremely poor especially during old age. It consists of a balloon which is positioned in thoracic-aorta and is then connected to an external machine that inflates and deflates the balloon rhythmically with helium gas filled inside it. During diastole, the balloon inflates and thus, more blood is carried to the coronary arteries. By this pump infact, the heart can be assisted in its working for many hours or days.

Angioplasty: In common parlance, this is also known as Balloon catheterization and is generally used for removing plaque or blockage in the blood vessels. In coronary arteries, the so called blockage generally occurs in right coronary which supplies blood to SA-node, AV-node and to Bundle of His, in addition to supplying blood to right atrium and right ventricle. To correct this disorder, a stent is placed surgically inside the body. A stent is basically a special device made of stainless steel that simply resembles a spring coil. It is permanently placed in an artery via a catheter so as to ensure an adequate supply of the blood to the heart muscles.

Defibrillator: A condition in which there is a rapid, irregular or so called asynchronous, ineffective and an uncoordinated contraction of the cardiac muscles is referred to as fibrillation of the heart. There is no doubt in the fact that almost 99% of the reported deaths of myocardial infarction cases are due to fibrillation (atrial) only. Although, ventricular fibrillation does occur and become a cause of death especially, in electrocution cases that eventually reduces stroke volume and blood pressure and hence, death occurs. A Defibrillator is a device that provides high voltage current to the chest muscles for just a fraction of the second and hence, restores the normal functioning of the heart muscles.

Heart Lung Machine:  It is used for open heart surgery or heart bypass surgery. This machine or instrument has two main components called as below:

?Oxygenator or Iron Lung and ?Roller pump or heart-substitute. The component called as the Oxygenator is used for the oxygenation of the blood may be of two types:

?Bubble oxygenator and ?Membrane oxygenator. The membrane oxygenators are generally costlier than the bubble oxygenators and thus, are used for the surgeries that are to be carried out over a longer duration of time. During the performance of a heart surgery, whole blood of the heart is by-passed through heart-lung machine.

Artificial Limbs: They are essentially external prosthetics and the most popular of such external prosthetics has been Jaipur foot. It was developed by Dr. P.K.Sethi and has been prepared from solid rubber, aluminum and wood and although being light in weight, but very strong in nature. Now-a-days, myoelectric arms through which the stimulus generated by the amputated part of the arm is transmitted to the fingers for their movement are also in use. Such arms can be used for holding objects or even for shaving etc.