Blood pressure
The Development and Concepts of Medical Equipment
Over View
Until the 19th century, medical technology was a small specialized world. Doctors in the 1800’s where solely dependant on their own senses and any instruments they possessed would have been designed and made by themselves or the local Blacksmiths.
The late 19th Century saw the advent sanitary engineering, clean water and safe sewage disposal. This did more to improve general health of the developed world than any clinical medicine.
The 20th Century saw a rapidly expanding world of technology. The introduction of anaesthesia, bacteriology, haematology, biochemistry and radiology. Doctors at the beginning of this period could have the use of laboratories and X-ray departments.
Since the 1950’s there has been an enormous growth of technology in laboratory medicine and in biomedical engineering.
Medical technology is for ever being researched and improved because of the needs of our health. Essentially there are two parts to medical technology : Diagnostic and Therapeutic, although prevention of disease requires medical technology of the most advanced.
Self awareness through improved schooling and organized health strategies
have seen people take more care of their personal health by recognizing
risks (smoking ) and through education, better diets and life styles
and learning to recognize the signs of disease to get treatment in the first instance to increase the chances of survival.
Developed in China, with the belief that a life-force is essential for good health, acupuncture is an ancient therapeutic technique .
The Chinese believe that the life energy (chi) flows through the body along pathways called meridians. Disrupted body functions or disease is considered the result of interrupted flow. The needles restore the flow to resolve health.
Method
Needles of length 0.5 to 5 inch (12 mm to127mm) are placed in specific
parts of the body to relieve a number of conditions from back pain to toothache,
neuralgia, headaches and even stopping smoking.
Alternative methods to acupuncture include pressure or heat being used in the place of needles.
Western medicine is increasingly accepting acupuncture as a treatment
and it is thought that a form of Anaesthesia may be induced by stimulation
of sensory nerves.
This would stimulate the pituitary gland and hypothalamus to release
endorphins (the body's natural painkiller).
If the patient has a strong psychological belief that it will work,
this could be contributory.
Pressure sores have always been a problem for patients who are confined to bed for long periods of time.
At the point on the patients body that makes contact with the mattress, a sore can develop that can ulcerate or become infected. It is inevitable that this would make the condition of the patient worse and slow down the recovery from first hospitalization, as there is a secondary treatment needed.
The patient must be regularly moved to a different position to alleviate the risk of a pressure sore.
Method
The idea of an Air bed is to reduce the need for turning as this is done to some degree automatically.
The mattress is constructed of cells that are alternately inflated. This is done by a compressor with two outputs that alternate between each other. The compressor can sense a leak in the mattress and sound an alarm.
There is a quick release C.P.R. plug to deflate the mattress in-case
of an emergency where the patient needs to be resuscitated.
History
Norman J. Holter, D.Sc. and associates developed a machine in the mid
1950’s that recorded ECG signals from leads on the chest and recorded
them onto magnetic tape for later analysis.
Now the Holter recorder is quite common and many people with suspect heart problems are instructed to ‘wear’ one for 24 hours.
Method
The ambulatory ECG recorder is the size of a personal stereo and is
worn on a belt or strapped to the patient. It has electrodes that are attached
to the chest and these pick up the ECG signal. This is then recorded onto
the cassette tape which runs slow enough for 24 hours recording.
The tape is then rapidly analysed by a machine that stops when it detects any abnormalities in the recording. The technician who controls the playback machine makes notes to report back to the physician.
Also, there is a ambulatory blood pressure machine available that will
make blood pressure recordings every five minutes and record 24 hours worth
of data. In a similar way as the ECG recorder, this machine downloads the
data to a PC that analyses the recording.
History
In the mid 19th century, anaesthetics ether, chloroform and nitrous
oxide were first used in Europe and the USA as pain relief during operations.
It was found that these substances dull bodily sensations, especially pain.
As the anaesthetic has become more refined, the recovery from an operation is better.
Method
Anaesthetic drugs act on the membranes of nerve cells and disrupt the
transmission of electrical impulses to the central nervous system. This
causes the sensation of numbness.
Local anaesthetic blocks electrical nerve transmission in the site where
it is administered
usually by injection.
Regional anaesthesia The anaesthetic is introduced to large nerves
or to an area of the spinal
cord that would supply a large area of the body.
General Anaesthetic is an initial injection that quickly dissolves
into the nerve cells of the
central nervous system and causing unconsciousness.
An Anaesthetic trolley is used where the patient then breathes inhalation
anaesthetic to
maintain anaesthesia.
The Anaesthetic trolley would be found in an operating theatre. It uses
different gases and
vapours which an anaesthetist will control to keep a patient anaesthetized.
Sometimes these
machines incorporate a ventilator and patient monitoring equipment
.
Often for neonate or paediatric use, an apnoea monitor detects breathing with a strain gauge affixed to the chest to detect the expansion or with electrodes that measure the change in impedance as the chest moves.
The device sounds an alarm if no breath is detected after a pre-set time. The alarm which is usually quite loud may actually startle the infant into breathing again. The audible alarm feature can often be switched off just to give a visual indication with flashing indicators.
An apnoea alarm is ‘loaned’ to a parent of a child by the clinician that may suspect breathing difficulties.
An apnoea alarm is also found in the operating theatre in conjunction
with ventilators which would monitor the breathing of the unconscious patient.
The alarm would alert the anaesthetist of a problem with the breathing
circuit or patient.
An Autoclaves is a pressure steam cleaners used to sterilize surgical equipment.
The surgical instruments are usually wrapped in a porous material and
sealed with indicating tape before being placed in the oven.
The air inside the oven is evacuated before the high pressure steam
is let in. Because the steam is under pressure it can get to a very high
temperature that would be pre-set on the front panel.
The steam contacts all parts of the instruments before the oven is then evacuated again. This action dries the instruments.
The indicating tape that sealed the wrapping, changes colour to indicate
that the process is complete and the instruments are sterilized ready for
use.
Babies need to be kept warm because they cannot control their body temperature as adults can.
These devices are often an overhead heater placed over the cot that contains an electrical heating element that is pre-set, or sometimes with a thermistor on the patients skin to control the thermostat.
A warm water filled mattress is also used that can be placed in a cot
that the baby is placed on.
History
In 1730 it is recorded that Reverend Steven Hales applied a canula
to an artery in the neck of a
horse. He measured the height of the blood in a glass tube to be over
8 ft (2.5 meters) above the heart.
In the late 1800’s an Italian Scipione Riva-Rocci used a Sphygmomanometer
to find the systolic
pressure.
A Sphygmomanometer is basically a pressure gauge in the form of a column
of mercury or an
analogue gauge and is used to measure blood pressure along with the
use of a stethoscope.
The idea of listening to the brachial artery to hear to the pulsatile sounds was noted by a Russian surgeon in 1905 called Nicholai Korotkoff. The Korotkoff sounds give indication of the Systolic - the point where the pressure in the cuff occludes the brachial artery and stops blood from passing through. This is also an indication of the greatest pressure that occurs in the artery during systole; at the height of contraction of the heart. And the diastolic - the lowest pressure in the cardiac cycle. It occurs during the last of diastole, which extends from the end of one contraction of the heart to the beginning of the next. The Diastolic is also considered a measure of the resistance of the vascular system and the elastic contraction of the vessels.
Method
Blood pressure is measured usually by the physician during a diagnosis.
For auscultatory
measurement, a bandage cuff is wrapped around the arm which contains
an inflation bag, and the
stethoscope is placed over the brachial artery. The cuff is inflated
30 mmHg above the
disappearance of the pulse which is seen as the loss of small pulses
on the gauge.
The cuff is slowly deflated and on hearing the Korotckoff sounds the systolic is recorded. As the cuff is further deflated, the sounds disappear and on reappearing the clinician listens for the softening of the sounds and just as they disappear, the diastolic is recorded.
The advent of automated devices now measure blood pressure automatically
and indicate the systolic and diastolic pressure visually. These units
often show the Mean pressure.
The Mean pressure is not the average of the systolic and diastolic,
but the mean pressure within the arteries during the cardiac cycle.
Breast milk can be drawn from the mother for bottle feeding.
A breast pump causes a low, adjustable suction and with the aid of a suction cup, the milk is drawn off and is placed into a container.
The milk can then be used to feed the baby with the use of a bottle.
A cautery machine used in a clinic is often an adjustable current output DC power supply with leads attached to a hand piece that holds a thin wire loop.
As the current passes, the wire is heated rapidly. The heat of the wire is controlled by the adjustable current.
The heat dissipated through the tissue causes coagulation and that can be used to stop bleeding or for cutting tissue.
The wire loop is self sterilizing as the heat passing through causes
the wire to be at a very high temperature.
Computerized Axial Tomography (CT or CAT Scan)
A Computerized Axial Tomography machine creates images of the internal
structures of the body and are used for diagnosis. The procedure was developed
by the British scientist Godfrey Hounsfield who constructed the first scanner
in the early 1970’s. The patient lies between an X-Ray source and an array
of detectors, which receive different amounts of radiation according to
the density of the tissue scanned. The source and detector array are rotated
around the
patient and the data is analysed by a computer and presented as a graphic
image of the ‘slice’. These slices can the be compiled by the computer
to produce stunning 3D images of the soft tissue structures.
Tomography is a sectional X-Ray. As the radiation is of a lower power
the patient doesn't receive large doses of X-rays.
CO2 monitoring is used during anaesthesia. Many potentially dangerous situations can be first detected using CO2 monitoring.
The anaesthetic gas breathed by the patient is continuously sampled by the device that passes the sample past an infra-red light source. The absorption of the light is detected and the results are displayed in a wave form and percentage concentration.
The wave form displayed clearly shows the breathing pattern of inhalation and exhalation.
The first gas exhaled contains no CO2 because this gas has been in the dead space (the neck, mouth and face mask) and not in the alveoli therefore no gas exchange has taken place. Eventually, during exhalation, the gas is purely from the alveoli and this is measured as ‘end tidal CO2’ or ETCO2.
On inspiration, the minimum level of CO2 is detected (0.0%) and this
is the inspired CO2.
A Cryosurgery device uses a gas, typically CO2 that is fed from a pressure reducing regulator to a hand held pistol grip with a trigger. Attached to the hand piece is a metal tip.
When the trigger is operated, the metal tip is rapidly taken to a very cold temperature, below freezing.
Used in theatres, special clinics and chiropody, the metal tip is rapidly
cooled on contact with the skin. The freezing action causes the tissue
to die and the surrounding area is coagulated.
A defibrillator is used when the heart goes into fibrillation. This is when normal electrical activity of the heart is in a confused state and the heart is out of sync with itself. In fibrillation the heart is pumping ineffectively and is in more of a spasm.
It was found that a ‘short sharp shock’ could bring the heart out of fibrillation and bring it back into its normal routine. Fibrillation could be caused by heart disease or an electric shock and can cause death within a few minutes.
The fibrillation signal is a rapidly oscillating wavy trace that can be monitored using the ECG on the defib (through the paddles or separate ECG leads).
A current is passed for a very short time through two paddles across
the chest, and the patients ECG signal is monitored and normal sinus rhythm
is looked for.
Dental surgeries have many different types of equipment.
Drill : The drill a dentist uses works from compressed air or an electric motor. The drill has a mandrel that takes different type of tools.
Suction : The suction machine is used to remove debris from the mouth.
Compressed air : Compressed air is used to look for cavities and sometime to remove debris.
Light source : The light source is used to get a clear view of the mouth.
Dental Chair : The dental chair has electric motors to enable the dentist to get the patient into the ideal position.
The dental unit would also have anaesthetic machines for use in general
surgery, along with oxygen and resuscitation equipment.
Small unwanted molecules can be removed from the patients blood if the kidneys have failed by the use of a Haemodialysis machine.
Dialysis is the process whereby crystalloid and colloid substances are separated from a solution by interposing a semipermeable membrane between the solution and pure water.
The substances pass through the membrane until equilibrium is achieved.
This is the principle upon which the artificial kidney works. When the
patients blood is used the process is known as Haemodialysis. When the
dialyzing fluid is passed into the abdominal cavity, and the peritoneum is used as the semipermeable membrane, the process is known
as Peritoneal Dialysis
These machines are high frequency generators that are used by surgeons during operations, to cut and coagulate tissue. They often incorporate suction and light source.
There are usually three modes to a diathermy, each with individual power controls : ‘Cut’, ‘Coag’ and ‘Bipolar’ and there is a colour coding yellow, blue and white/ black respectively for the control pedals.
An adhesive ‘plate’ electrode is placed on the buttock or thigh. The ‘active’ electrode is attached to the forceps or hand piece and is used at the site of the operation.
When Cut mode is selected, the surgeon uses the active electrode to cut the tissue, as the pedal is pressed. The current generated by the diathermy passes from the active electrode where the power is concentrated, and is dispersed through the patient to the plate.
‘Coag’ can be selected, and the forceps will coagulate tissue when the surgeon operates the foot pedal.
Diathermy uses high frequency because muscle tissue will not contract as it would if the current where D.C. or low frequency A.C.
These machines alarm under certain conditions and disable the output.
i.e. if the plate electrode becomes unattached to the patient, if the patient
touches earth, or if the plate voltage becomes too high.
History
Johann Christian Doppler (1805-1853) first put forward the principle
of the phenomena we now know today as the Doppler effect. The phenomena
affects all waves when the source and receiver are moving relative to each
other.
Simply, a motor engine could be the source and your ear could the receiver. As the motor engine moves away from the ear, the note of the exhaust appears to go lower in tone. The shift in tone is the Doppler effect.
The first measurement of blood flow in the heart was by Satomura in 1956.
Method
Bats use ultrasound to visualize their environment similar to the way
echo cardiograph machines work to give images of the heart.
The sound waves are pulsed into the Piezo crystals that project the sound. In between the pulses, the Piezo crystal is used to ‘listen’ for an echo.
As the ultrasound penetrates tissue, the sound is absorbed or reflected. The strength of the echo depends on the density of the tissue. The results are displayed on a monitor where the intensity of the echo is shown in grey scales or colour.
Alternatively, the results of the echo are amplified to a loudspeaker
where one can hear the pulsation's of blood flow or fetal heart.
E.C.G.
History
Einthoven gave an alphabetical lettering to the ECG (electrocardiograph)
wave form because he did not know the origins and did not wish to suggest
interpretation by his labelling.
Method
Muscle cells are surrounded by a semipermeable membrane which allows
sodium ions to pass
through. When the cell is at rest, there is a larger concentration
of sodium ions outside the cell than are in it. You could measure about
-90mV across the membrane.
When the cell is excited by a stimulus, the membrane begins to move sodium ions into the cell and the potential across the membrane would become less negative. The membrane has a threshold (about +40 mV) where it peaks, and starts to transport the sodium ions back out of the cell.
Depolarization is the act of going from -90mV to +40mV. During depolarization,
the muscle cell
contracts.
Repolarization is where the membrane transport sodium ions back out
of the cell. During
repolarization, the muscle cell relax.
The basic ECG wave form represents a voltage level of the heart muscle,
and consists of three
recognizable deflections. The p wave , the QRS complex and the T wave.
The depolarization of the atria is represented by the ‘p’ wave, where the
atria are contracting, forcing blood into the
ventricles.
‘Q’ is the point where the ventricles begin depolarizing and contracting.
The time between ‘q’ and ‘s’ immediately precedes full contraction of the
ventricles when blood is being forced into the arterial system. The ‘t’
wave represents the refractory period of the heart when the ventricles
are depolarizing.
History
First used by Berger (1924), an ELECTROENCEPHALOGRAPH (E.E.G.) is a machine that detects and records electrical activity in the brain. It does this by measuring potential differences (voltages) between electrodes placed on the scalp.
The EEG machine may have up to sixteen channels that measure brain activity occurring as the result of ‘feeble currents’. The EEG signals are distinguished by their frequency and by the region of the head in which they arise.
ALPHA WAVES (8-13 Hz) found in the occipital region are associated with relaxation and BETA WAVES (15-30 Hz) in the frontal region.
Use in Neurology to diagnose disorders of the brain caused by epilepsy,
and sometimes tumours, the machine requires skilled clinicians although
the advent of computers have brought new machines that provide diagnosis
for doctors.
This technique enables the surgeon to see inside the body using special optical lenses and fibres.
The endoscope is inserted through natural orifices or small incisions
and light is guided down along with specially designed surgical instruments.
Endoscopes now incorporate cameras and the pictures can now be displayed
on a video screen.
The fetal heart can be monitored using ultrasound probes attached to the mothers abdomen whilst in labour.
Pulsation's of the fetal heart are heard through a loudspeaker and the fetal heart rate is displayed digitally. Also, the heart rate is printed on a graph over time to show any variations.
Additionally, these devices incorporate transducers that measure the
contractions with the use of a strain gauge also attached to the abdomen.
The result of this is plotted along side the fetal heart rate, thus enabling
the midwife to observe the increasing intensity of the contractions.
Hand held fetal heart detectors are used in ante natal clinics and by
midwives who use the instruments to check for the fetal heart.
There is special equipment available to assist those who are deaf or hard of hearing.
You may realize that many everyday items utilize an alarm or sound to warn you or catch your attention.
Sound activated systems are devices that attach to telephones and doorbells and flash lights or use vibrating pagers to alert the user.
There are unique devices such as smoke alarms to alert you if you are asleep and Baby alarms that operate vibrating pads, and that flash lights.
Some telephones are hearing aid compatible, which means that you can switch your hearing aid to ‘t’ and the sound is amplified while background noise is cut.
On some videos there are hidden captions that can be viewed when you
use a special box to plug into your video. Contact : movietext@compuserve.com
for more information.
The heart lung machine replaces the function of the heart and lungs during surgery on these organs. The machine was first used by Gibbon in 1953
The machine circulates the patients blood through a special peristaltic
pump, designed not to damage the cells in the blood. The blood is passed
over a permeable membrane where a gas exchange takes place. Carbon Dioxide
is removed from the blood and oxygen is absorbed by the blood. This gas
exchange mimics lung function and the peristaltic pump replaces the heart,
pumping the blood around the body.
A humidifier is used when the patient is anaesthetized or during ventilation
to enrich the gases with water vapour because the gases used are too dry.
The definition of hyperbaric is “ at higher than normal pressure (esp. oxygen)”.
Originally pressurized vessels were developed to combat decompression
sickness suffered by deep sea divers. If a diver surfaces too quickly,
molecules of nitrogen form into bubbles in the blood and cause the ‘bends’.
This can be overcome by placing the patient in the chamber, increasing
the pressure until the nitrogen is forced back into solution within the
blood and
then slowly reducing the pressure in a controlled way to stop the bubbles
forming. This process is akin to opening a pop bottle too quickly and watching
the carbon dioxide gas come out of solution .
It was later discovered that an oxygen rich atmosphere within the vessel aided the application of oxygen therapy and accelerated the healing of wounds.
Deep sea divers are sometimes transported from one dive site to
another in hyperbaric chambers to avoid long inter dive decompression times.
Incubators
Premature babies and under weight babies are placed inside heated incubators because they cannot control their body temperature.
The incubator has an electrical heating element that is controlled by thermostats. There is a fan that circulates the heat to get an even distribution.
The temperature is set usually to about 35 ‘C and temperature stabilized before the baby is put in.
Most incubators incorporate oxygen controllers so that a specified oxygen concentration can be set, and humidification.
Incubators alarm at over temperature, fan fail, mains failure and oxygen
over/under concentration.
Infusion
Infusion devices are mechanical pumps used to administer liquid drugs in-vitro from a fluid filled bag via a giving set.
Flow rate and volume infused can be pre-set as can sometimes the maximum pressure in the line.
Often, the infusion device has inbuilt sensors to detect air in the line and pressure sensors to stop the pump in the event of a blockage or occlusion.
The most common form of infusion pump uses a peristaltic mechanism to
drive the fluid through the line. A drop sensor connected to the device
and attached to the drip bag counts the drops and checks for loss of flow
or over infusion.
History
Insufflators inflate the abdomen so that laparoscopes can move more
easily around the organs.
H. Fragenheim introduced a prototype automatic insufflator in the 1950's
Method
A cannula is passed through the skin into the peritoneum and is connected
to the Insufflator.
The inflation is called a "pneumoperitoneum", carbon dioxide being
the most common gas used.
The gas flow is controlled between 1 Lt /min and 10 Lt /min at a pressure
of approximately 15 mmHg
History
The Iron Lung was used in the treatment of respiratory disease, paralysis
and in anaesthesia but most extensively during the poliomyelitis epidemics
of the 1930’s and 1950’s.
Method
The Iron lung is a device that provides artificial respiration by mechanical
means.
Negative pressure units are a sealed vessel containing the patients body with the head protruding with a seal around the neck. The rhythmic removal of the air from the vessel forces the patient to take in air through the nose and mouth.
Positive pressure units (ventilators) force air into the lungs through
a close fitting tube into the trachea.
History
A urethroscope was designed and built by Segalas of France in 1826.
He used an introductory cannula and mirrors for light.
Kalk of Germany has been dubbed ‘the father of laparoscopy’. He wrote papers on the subject from 1929 to 1959 and he devised a foroblique viewing system for use on his work with liver and gallbladder disease. It is his methods that have widely been adopted and are in use today.
Method
Laparoscopes are long narrow tubes that contain lenses and mirrors that
a surgeon uses to look inside the body.
This method is minimally invasive because only a small incision is made through which the laparoscope is passed.
Used with an insufflator, and a light source, the laparoscopes is inserted into a small incision and can be moved easily around the organs.
The recovery of the patient is easier than that of general surgery because
of the minimal invasion.
Laser
A Laser is an instrument that amplifies light waves by stimulation to produce a powerful coherent beam of monochromatic light.
This intense beam of light that can be used to cut or coagulate tissue. The precise accurate aiming of the beam results in the laser being used for extremely fine surgical procedures, for example, on the eye with very little scar damage and fast healing. Laser surgery is less invasive than normal surgery, it destroys diseased tissue gently and allows quicker, more natural healing.
Laser treatment can also be directed down flexible endoscopes into the body allowing even less surgery than would otherwise be required.
Light Source
History
Bruck, a Dentist from Breslau, made a platinum wire loop which he heated
with electric current in 1867, but before the light source was readily
available, mirrors were used to reflect the light onto the subject.
Method
It is essential for the clinician or surgeon to have a clear view and
see clearly at what they are working.
The fibre light source is used during surgery to give the surgeon a
clear view through an endoscope or laparoscope.
The clinician needs to have accurate measures of the patients lungs to aid the observation or diagnosis of pulmonary problems.
Accurate measures of lung capacity and forced flow are taken and compared to predicted values.
The patients age and height are taken into account before the results
are compared to statistics.
The equipment in use in maternity departments is primarily aimed at the baby, although there are breast pumps, thermometers, oxygen therapy, and patient weighing scales used on the mother.
Other equipment may include an incubator, overhead heater, heated cots,
Magnetic Resonance Scanner (M.R.I.)
Magnetic Resonance Scanning (sometimes called Magnetic Resonance Imaging “MRI” or nuclear magnetic resonance imaging “NMR”) is a relatively new technique used to investigate the body for diagnostic purposes and has the advantage that it does not use ionizing radiation (X-Ray).
It comprises a large circular magnet that determines the magnetic bearings of a number of atom nuclei in the body.
As the magnet is switched on, some atoms in the body are excited by radio waves. The atoms move into a high energy state and give off a weak radio signal that is picked up and sent to the computer that displays the information as an image.
Different radio wave frequencies represent different elements of tissue.
The procedure is totally painless, but sometimes an injection is needed
(radio opaque die) to enhance the scan.
Intricate surgery can be performed using microscopes and precision surgical instruments during brain, ear and eye surgery, and severed limbs.
This has only become possible in recent years.
Microsurgery relies on the highly trained surgeon who can connect together
the ends of nerves, arteries, veins, or muscles to enable the nutrition
required to preserve tissue.
Used in the treatment of certain respiratory ailments, a nebulizer is a machine that converts the liquid medication into a fine mist that the patient can inhale.
Nebulizers are air compressors that are powered from mains and give an output of about 15 P.S.I. at a flow rate of about 2 Litres per minute.
Tubing is attached to the output of the compressor and the other has a chamber that holds the fluid drug and a face mask.
The pressure from the nebulizer forces the drug through a small hole that creates a mist that the patient breathes in.
The aerosol mist that is breathed ensures that the drug is administered direct.
They have a filter on the air intake that should be regularly replaced.
One of the first requirement of a physician is to be able to see the
cause of the patients problem. Originally doctors used natural light and
a head worn reflector.
Today there have been many improvements and there are a huge number of
optical devices in the modern hospitals.
Video Camera systems
The advent of smaller video cameras has enabled this branch of optical
medicine to be at the forefront of surgical techniques. Video systems are
used in theatres with laparoscopes or endoscopes enabling the surgeon to
view on the video monitor internal structures, problems or diseases. The
ability to record exactly what the surgeon sees during a procedure gives
the opportunity to view the operation, or investigation, later for
analysis or training.
Endoscope, long fibre optic bundles inserted into natural orifice to view internal structures.
Microscope, used in laboratory for looking at clinical samples, in theatres
during surgery, and clinics for ENT. Theatre Microscopes are very solid
mounted structures slung from the
theatre ceilings so that the surgeon can swing powerful microscopes
directly over the patient. This invention has allowed the progression of
microsurgery on both eyes, nerves and other microscopic structures.
Slit lamp, used for looking into the eye.
Ophthalmoscope, used by clinicians for looking into eyes, nose, or throat.
Otoscopes, used to look into the ears.
Oxygen is a colourless, odourless gas slightly heavier than common air. It was discovered by Joseph Priestley in 1772. It forms approximately one fifth by volume of the atmosphere.
Oxygen is necessary to life and the process of respiration has, as one of its main objectives, the supply of oxygen to the blood.
Oxygen is compressed and stored in bottles under very high pressure (300 bar). The pressure is reduced to 4 bar by a regulator screwed onto the bottle which is either piped to the ward and a flow meter is plugged into the outlet, or a flow meter is mounted onto the regulator to make it portable.
Flow rates are adjustable and vary from 0 to 1 Litre Per Minute in 0.1 graduations for neonatal use, and from 0 to 15 L.P.M. for adult use.
Oxygen is used on ambulances for emergency administration, and is found in all parts of the hospital both in bottled form and piped to the wall outlets.
Applied to unbroken skin oxygen has little effect, but when applied to a wound or ulcer, it increases circulation and therefore healing. The condition of oxygen want is called anoxaemia and can be caused by damaged lungs or by circulatory problems.
Oxygen can also be applied under pressure in a hyperbaric chamber, usually
at about 3 bar. Under these pressures healing of wounds can be accelerated,
infections and coronary thrombosis can be treated and carbon monoxide poisoning
can be reversed.
Early civilizations perceived concepts such as the magical influence
of the spirits of the dead, a punishment for sins committed as some of
the causes of pain. Plato viewed pain as an “effective” experience, that
is an emotional experience, caused by a violent intrusion of elements of
the body. He also thought the heart to be the centre of all sensitivity.
Aristotle agreed with Plato, but did not include pain as one of the 5 main
senses. He believed it to be the opposite to pleasure.
In the 2nd century a Roman called Galen believed the brain was the
centre of all sensation, not the heart.
In 1664 Descartes proposed that the pain system was a straight through
channel from the skin to the brain. Bell and Magendie in the 1800’s proposed
scientifically that it was sensory nerves which conveyed messages from
outside to the brain. In 1842 Johannes Muller recognized pain as a variety
of the touch sensation.
Physiotherapy
Physiotherapy equipment is many and varied. Heat is a common treatment often used in the form of hot wax, and more physical treatments include traction.
Electrotherapy is used to treat muscle pain and strains in the form of interferential. This is a differential treatment that produces two independent sets of stimulating currents at different frequencies that can be pre-set.
Each set of skin electrodes are placed at opposite sides of the affected area. Where the stimulating currents cross over, there is an interference that produces the treatment region.
Ultrasound is used to generate heat in the body that can be applied
to the affected area to treat pain, injury and inflammation.
Positron Emission Tomography (PET)
History
Positron Emission Tomography was developed in the 1970’s with the advent
of the computer which produces the final image. PET is a technique of nuclear
medicine and now with smaller particle accelerators the technique may become
more widespread.
Method
PET is used to monitor biochemical and physiological changes within
the body using a ‘labelled’ radioactive isotope that has a short half life.
It is known that different parts of the body absorb or metabolize certain substances in definite ways. For example : fluroro-deoxyglucose that is ‘labelled’ can make glucose metabolism in the brain “visible”.
The substance is administed and traced. It is possible to provide
information on cerebal palsy and the metabolism of brain tumours.
Pulse Oximeter
History
Carl Matthes (USA) in 1935 built the first machine to measure human
blood oxygen saturation, and in 1951 a paper was published that declared
oximeters were capable of detecting low oxygen saturation levels before
any clinical evidence of cyanosis. Hewlett- Packard invented an ear oximeter
in1970 but it was in 1974 that Takuo Aoyagi discovered pulsation's in the
signal.
Scott Wilber produced a sensor with cable to connect it to the instrument, and he recorded human volunteer data to improve the reliability of saturation estimates. It is from such statistics that modern pulse oximeters give their results, as they use empirical values in a ‘look-up table’ with a microprocessor.
Method
Oxygen is carried by the blood to tissue where it is required. Oxygen
is carried mainly by a
protein called haemoglobin.
One molecule of haemoglobin can carry up to four molecules of oxygen which would then be 100% saturated, and therefore a pulse oximeter measures the oxygen saturation of haemoglobin in arterial blood.
A pulse oximeter shines two different wavelengths of light through a finger or ear lobe. Some of the light is absorbed by tissue depending on the level of oxygenated haemoglobin. A photo detector sends the signal to the microprocessor which determines how much oxygen is saturated in the blood.
The device also measures the pulse rate which is displayed along with
the oxygen saturation and the wave form of the signal.
Radiology is the application of radiation for diagnostic or therapeutic purposes.
X-ray is used to detect broken bones and chest infections, but techniques have been developed where a non-toxic radio opaque substance (e.g. barium meal) are administered to show the internal organs that do not show up on normal X-ray.
An image intensifier displays the X-ray image on a monitor and can convert
the image to a digital format for easy storage. The image can be enhanced
digitally thus the dosage of radiation can be reduced to the patient.
Radiotherapy is the use of ionizing electromagnetic radiation (X-ray and Gamma ray) for the treatment of disease such as cancer.
Before the 1930’s radium was physically inserted into tumours through hollow needles. Now teletherapy is used in which controlled irradiation is administered from a distance of 1 metre or more.
X-ray was superseded by radioactive isotopes radium and cobalt 60 and then by particle accelerators.
A critical factor of radiotherapy is dosage and the treatment tends to be used on localized forms of cancer as normal tissue is sensitive to radiation.
Radiotherapy is often used in conjunction with surgery and cytotoxic drugs.
Tumours are accurately identified with computerized axial tomography (CAT) and modern radiotherapy machine deliver an accurate, precise dose of radiation.
Side effects are reduced because of lower intensity dosages given
over a period.
In any emergency, resuscitation equipment needs to be close to hand.
Equipment may include oxygen, suction, a portable ventilator, or a defibrillator.
History
Ophthalmologists started examining eyes by using hand held loupe's.
The mounted microscope and head cradle replaced this and later the slit lamp was added. Slit lamp microscopy was pioneered by Alfred Vogts. His descriptions and observations were seen at the time as the definitive study of the eye.
Method
A slit lamp is used to look for foreign bodies or defects in the eye.
Improvements in optical design and image analysis have taken this instrument much further although the basic design remains.
A chin rest holds the head still and an adjustable beam of light
shines into the eye while the clinician looks through the magnified image.
In some cases of heart disease, one way to carry out investigations is to put the heart under some stress. This is usually done by having the patient walk on an gradient adjustable treadmill, which will be controlled by a computer.
The patient will be connected to an ECG recorder. The test, of which
there are several profiles, will then slowly increase the gradient of the
treadmill to make the heart work a little harder. The computer monitors
the patient, making sure it doesn't push the patient too far, and records
the stress versus heart response.
From this data the clinicians can decide on the required treatment.
Sound level meter
A sound level meter can be used to measure levels of ambient noise
from conversations in specified areas.
Suction machines are powered from mains or sometimes from battery.
An electric motor drives a mechanical pump that creates an adjustable suction usually of maximum -700 mmHg
They are used with catheters for drainage purposes from oral (in the
case of resuscitation) or surgical sites during operations.
History
There is evidence that early man operated on each other with various
“instruments”, Stone Age people may have even practised acupuncture !
The earliest types were probably flint tools used for trepanning the skull. Later the Ancient Greeks and Hindu surgeons used steel knives, scissors, forceps and needles. As the need for cleanliness became apparent, wooden handled instruments were superseded by all metal instruments suitable for sterilization.
Steel was first nickel plated and then replaced by stainless steel as
the preferred material.
New materials are constantly being brought into use such as titanium,
ceramic and plastics.
Syringe Driver
Once a syringe has been filled with a drug, it can be mounted onto a syringe driver that will inject the drug at the rate that the clinician sets.
Some syringe drivers automatically detect the size of syringe and ask the user to confirm the syringe size. Others, you must use the correct size syringe.
Then the user must set the flow rate. Also the volume to be infused can be set.
The syringe driver will detect an occlusion (a blockage), stop and alarm.
Most syringe drivers have internal rechargeable batteries so that the
patient can move if needed and the device will still work.
Transcutaneous electronic nerve stimulators (Tens) are used to treat pain or injury.
The device is powered with a battery and electrode pads are placed on the skin.
The machine gives an output that can be preset, of pulsed electrical stimulation of varying degrees of intensity and frequency.
The concept of electrical stimulation for pain relief is far from modern. The first recorded use was some 2000 years ago, by the Roman Physician, Scribonius Largus. He applied electric eels to haemorrhoids, arthritis, headaches and gout sufferers.
Although there is some evidence of electrotherapy in the Middle Ages, it was not until the early 19th century that the next recorded details appear.
Duchenne De Boulogne developed the earliest forerunner to the TNS machine in the mid 1830’s, using cloth covered electrodes on the skin over the points of entry of the muscular nerves.
Faraday developed the electromagnetic generator producing alternating current in 1831.
This lead to excessive charlatanism and Electro-Quackery, including claims to cure not only pain, but such problems as poisoning and sexual impotence.
By the 20th century continued advances in the field resulted in such developments as the cardiac pacemaker. TNS was introduced into clinical practice following Malzark & Wall's “ Gate control theory “
The TNS machines are usually battery powered with 1 or 2 sets of electrodes.
The electrodes are positioned over the path of a peripheral nerve innervating
the painful area. For pain relief, the stimulation should be increased
until it can be accepted, without being uncomfortable, the recipient should
experience paresthesia at the site of the pain.
Thermometers
History
Two temperature scales are available in modern thermometers in hospitals,
Celsius (formerly centigrade) named after Anders Celsius and Fahrenheit
developed by Gabriel Daniel Fahrenheit. Celcius is more commonly used.
Thermometers using a mercury column are slowly being phased out because of the toxic content in favour of electronic units that give quick and reliable results.
Method
The electronic thermometer has a probe which is placed in a disposable
cover and placed in the mouth or under arm.
The probe contains a thermocouple whose resistance changes proportional to heat applied. This resistance is measured by the unit and the result displayed digitally.
Some electronic thermometers have antitheft devices built in that alarm
when the unit is removed from the building.
Treatment couches are used whenever a patient is to be examined by a physician.
The patient is asked to lie on the couch which may have adjustable height, backrest, or tilt. The adjustment may have simple mechanics with levers and brakes or hydraulic struts and sometimes with electric motors.
The treatment couch is an invaluable tool that requires little maintenance.
History
In 1956, Satomura used ultrasound for the first measure of blood flow
in the heart.
Ultrasound is used in many applications in the medical field. For example, echocardiography in cardiovascular, fetal heart monitoring in maternity, vascular blood flow in theatre, and physiotherapy as heat treatment.
Method
Piezo crystals can be exited with an electric current. As current passes
through the crystal it emits a wave of sound directly proportional to the
frequency of electric current.
A piezo can also be used to detect sound (Doppler). As the wave hits the surface of the piezo, a voltage is generated across it.
In the case of ultrasound scanners, the piezo is pulsed with electric
current and then used to hear for the echo. The strength of the echo depends
upon the density of the material being analysed and the results are displayed
as a grey or colour scale.
History
Originally problems were assessed by simple timed observations of fluctuations
in collecting tubes fed from indwelling catheters. More recent advances
have allowed machines to be developed that can carry out a host of investigations
Method
Uroflowmeters actually plot the flow and volume of urine against time.
The data is collected via the weight of urine voided, by dipstick capacitive
measurement, depth / pressure measurement or current analysis of a spinning
disc onto which urine is voided.
Urodynamic Systems offer a complex series of tests that can show urethral pressures, bladder function, muscle tone and flow / volume data. They also profile peak flow, flow instability and can carry out fluid filled cystometry tests.
A ventilator is a breathing machine used in anaesthesia, intensive care, and for emergency resuscitation.
Often powered by compressed gas, ventilators force the patient to breath or assist in breathing to an adjustable preset pattern.
Inspiration and Expiration times can be independently set, as can Cpap (constant positive airway pressure), PEEP (peak expiratory end pressure), and tidal volume.
In built alarms monitor conditions and are triggered by loss of pressure.
Vital signs machines consist of Blood pressure, ECG, pulse oximetry, and temperature measurement.
These devices are often very portable, being mounted on stands. The compactness of these machines is ideal as there is no need for several different pieces of equipment.
The blood pressure measurement is non-invasive and measured with an inflatable cuff (usually around the arm), the ECG is measured from electrodes placed on the chest and the pulse oximeter measured with a finger probe.
The vital signs monitor would be microprocessor controlled with a digital
display showing all results of measurements and often have an in-built
printer. Also there would be battery back-up to make the unit fully portable.
X-Ray
History
Discovered in Germany in 1895 by Wilheim Rontgen X-ray is now used
in a wide variety of fields.
Method
X-Ray is a form of Electromagnetic Radiation that has a greater energy
than light because it has a shorter wavelength.
An x-ray beam is produced by allowing a beam of high energy electrons to strike a tungsten target. The target is attached to a water cooled copper anode with an evacuated glass envelope.
The x-ray has differing extents of penetration and has the ability to affect photographic material. This is used to produce an x-ray photograph which would show fractures, infection and foreign bodies.
Also substances opaque to x-rays such as barium sulphate are used to visualize body organs. For example gastro-intestinal disorders.
High energy x-rays are used in radiotherapy to destroy tumour cells in Cancer treatment.
See RADIOLOGY
Weighing Scales
One of the first experiences that a human may encounter is that of being weighed.
The weight of a baby is possibly the first statistic recorded in it's life and the weight is closely monitored over the following days.
Patients are weighed on a daily basis and the results are plotted on a chart, thus the clinician can clearly see any fluctuation in weight.
It may easily be forgotten that the weighing scale is a delicate device that is works with balance on ‘knife-edges’ and this can easily be damaged if mistreated.
Often false recordings are made because of a weight chart left hanging
on the end of a scale.
