Session 2 Lec 3 Heat and Cold in Medicine

Session 2
Lecture 3: Heat and Cold in Medicine
Lecture Objectives:
Definition Temperature
Types of thermometers
Heat Therapy
Heat Therapy Methods
Use of Cold in Medicine
Cryogenic method
Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Specifically, temperature is a property of matter.
Types of thermometers:
The most common way to measure temperature is with glass thermometer, containing mercury or alcohol. For the thermometer to measure fractions of temperature degree, it requires capillary diameter to be so small (< 0.1 mm).
It has restriction just above the bulb.
Thermistor: Special resistor changes its resistance rapidly with temperature ~ ( 5% ) C? , Resistance are equal the bridge is balance.
This used in medicine because of its sensitivity (0.01 C?).
Thermistor is placed in the nose to monitor breathing rate by showing
temperature change between inspired and expired air and this type called
pneumograph.
Thermocouple: consist of two junction different metals; if the two junctions are different temperature, voltage is produced. This can be made small enough to measure the temperature of individual cells.
Thermograph – mapping the body temperature.
Measurements of body surface temperature indicate that it varies from point to point depending upon metabolic and circulatory processes near the skin.
In 1950 it’s found that most of breast cancers characterized by an elevated skin temperature in the region of the cancer.
The surface temperature above tumor ~ 1 C? higher than normal surrounding tissue.
If the temperature is sufficiently high (red hot), the radiation is visible. At body temperature the emitted radiation is in the infrared (IR) region.
Boltzmanlaw: For the total radiated power per surface area (W):
W= e ? T4
T = temperature ? =Steven Boltzmann constant = 5.7 X 10- 12 w / cm2 K4
e = 1 for radiation body
Heat therapy:
Two primary therapeutic effects take placed in a heated area:
Increase in metabolism ? relaxation of capillary ? vasodilatation.
Increase blood flow as blood moves to cool the heated area.

There are many methods of producing heat in the body:
Conductive heating
Infrared heating
Radio wave heating (diathermy)
Ultrasonic wave heating
Heat from diathermy used in treatment of inflammatory diseases of the joints (arthritis), bursitis & neuralgia.
Short wave diathermy used in reliving muscle spasm & bursitis.
Microwave diathermy is used for fractures, sprains, strain bursitis & injuries
to tendon.
Ultrasound used to relieving tightness & scarring occurs in joint diseases.
Use of cold in medicine:
Cryogenic methods used to destroy cells & this application called cryosurgery
Cryosurgery has several advantages:
There is minimal bleeding.
The volume of tissue destroyed can be controlled.
There is little pain sensation.
One of first use of cryosurgery was in treatment of Parkinson disease (shaking palsy).
Parkinson disease causes uncontrolled tremors in the arms and legs, it is possible to stop tremors by destroying the parts of thalamus in the brain that control the transmission of nerve impulses to other parts of nervous system.

Cryogenic method also used in several types of eye surgery we discuss two:
The repair of detached retina and cataract surgery ( the removal of darkened lens)
In surgical extraction of the lens, a cooled probe is touched to the front surface of the lens, the probe sticks to the lens making lens easy to remove.
Caution should be taken, when cryogenic liquid or cooled gasses are used, because any contact between this materials and the eyes or skin results in freeze burns. The most care is required when oxygen is used because many materials do not burn in air will burn in pure oxygen.
Much interest has been aroused by the idea of using cryogenic methods to cool the body into state of suspended animation so that it can pass time without aging. This science is called Cryonics