REGULATION OF TEMP. ILLUMINATION & HUMIDITY IN OR DR.FATMA ALDAMMAS

MEASUREMENT OF TEMPERATURE DEFINITION »Temperature --- is an expression of the thermal state of a body i.e., an expression of the kinetic energy of its mlecules. » heat ---which is the energy that can by given or taken from a body. DEFINITION »Temperature --- is an expression of the thermal state of a body i.e., an expression of the kinetic energy of its mlecules. » heat ---which is the energy that can by given or taken from a body.

MEASUREMENT OF TEMPERATURE When heat is added to a body, the kinetic energy of its molecules increases, and its temperature rises. The reverse occurs when a body is cooled. When heat is added to a body, the kinetic energy of its molecules increases, and its temperature rises. The reverse occurs when a body is cooled.

Temperature Regulation in the Body

The body performs a delicate balancing act between the heat generated in the body and the heat lost from it.

Types of Heat Loss Convection Evaporation Respiration Conduction Radiation

MEASUREMENT OF TEMPERATURE A change in the temperature of a body is accompanied by changes in all its properties » density »Visccsity »Elastisity »electric conductivity »resistivity. This fact has been used in construction of thermometers. A change in the temperature of a body is accompanied by changes in all its properties » density »Visccsity »Elastisity »electric conductivity »resistivity. This fact has been used in construction of thermometers.

MEASUREMENT OF TEMPERATURE Temperature Scales 1.Celsius Scale (centigrade): The zero point is the melting point of ice, and the point 100°C, is the boiling point of the water at standard pressure (760mmHg) 2. Kelvin Scale (absolute): The zero point is -273C, and the degrees are of the same size as the Celsius scale. 3.Fahrenheit Scale: The zero degree Celsius corresponds to 32°F. Temperature Scales 1.Celsius Scale (centigrade): The zero point is the melting point of ice, and the point 100°C, is the boiling point of the water at standard pressure (760mmHg) 2. Kelvin Scale (absolute): The zero point is -273C, and the degrees are of the same size as the Celsius scale. 3.Fahrenheit Scale: The zero degree Celsius corresponds to 32°F.

MEASUREMENT OF TEMPERATURE »To change from ºC to º F: F = (C x 9/5) + 32 »T change from °F to °C: C=(F- 32) x 5/9 »To change from ºC to º F: F = (C x 9/5) + 32 »T change from °F to °C: C=(F- 32) x 5/9

MEASUREMENT OF TEMPERATURE S.I. Unit of Temperature »The degree Kelvin (°K) is the S.I. unit of temperature » accepted that in General practice the temperature is expressed in ºC because in both scales the degrees are of the same size. 0°K. = -273°C. 273 ºK.= 0°C. S.I. Unit of Temperature »The degree Kelvin (°K) is the S.I. unit of temperature » accepted that in General practice the temperature is expressed in ºC because in both scales the degrees are of the same size. 0°K. = -273°C. 273 ºK.= 0°C.

MEASUREMENT OF TEMPERATURE Thermometers »A thermometer is a device which measures temperature. »There are three types of thermometers Thermometers »A thermometer is a device which measures temperature. »There are three types of thermometers

MEASUREMENT OF TEMPERATURE Types of Thermometers 1. Expansion Thermometers »Physical principle: When a solid is heated, its dimensions are changed. Similarly, when a liquid or a gas is heated, its volume is changed. Types of Thermometers 1. Expansion Thermometers »Physical principle: When a solid is heated, its dimensions are changed. Similarly, when a liquid or a gas is heated, its volume is changed.

MEASUREMENT OF TEMPERATURE Types of Expansion Thermometers »A. Liquid—Filled Thermometers. »B. Bimetallic Thermometers. »C. Bourdon Gauge Thermometer Types of Expansion Thermometers »A. Liquid—Filled Thermometers. »B. Bimetallic Thermometers. »C. Bourdon Gauge Thermometer

MEASUREMENT OF TEMPERATURE Types of Expansion Thermometers »A. Liquid—Filled Thermometers: The commonest type is the mercury-in glass thermometer. Its accuracy is °C. It is convenient for general clinical use but usually unsuitable for the requirements of operating theatres especially when marked and rapid changes of temperature are expected to occur, e.g., in induced hypothermia. Types of Expansion Thermometers »A. Liquid—Filled Thermometers: The commonest type is the mercury-in glass thermometer. Its accuracy is °C. It is convenient for general clinical use but usually unsuitable for the requirements of operating theatres especially when marked and rapid changes of temperature are expected to occur, e.g., in induced hypothermia.

MEASUREMENT OF TEMPERATURE disadvantages: »1. limited range »2. fragility »3. necessity for repeated shaking »4. slow response time »5. inability to obtain a permanent record disadvantages: »1. limited range »2. fragility »3. necessity for repeated shaking »4. slow response time »5. inability to obtain a permanent record

MEASUREMENT OF TEMPERATURE These difficulties can be overcome by using an electric thermometer.

MEASUREMENT OF TEMPERATURE B. Bimetallic Thermometers »Principle: solids change their dimensions by different amounts when their temperature changes »A bimetallic thermometer consists of two thin metal strips having different coefficients of linear expansion together and coiled to form spiral. B. Bimetallic Thermometers »Principle: solids change their dimensions by different amounts when their temperature changes »A bimetallic thermometer consists of two thin metal strips having different coefficients of linear expansion together and coiled to form spiral.

MEASUREMENT OF TEMPERATURE B. Bimetallic Thermometers » One end of the spiral is is attached to a pointer. » The spiral winds or unwinds as its temperature changes. »The movement is transmitted to the pointer which moves on a dial scale. » it is used for measuring atmospheric temperature, but it is not very accurate. B. Bimetallic Thermometers » One end of the spiral is is attached to a pointer. » The spiral winds or unwinds as its temperature changes. »The movement is transmitted to the pointer which moves on a dial scale. » it is used for measuring atmospheric temperature, but it is not very accurate.

MEASUREMENT OF TEMPERATURE C. Bourdon Gauge Thermometer »Consists of a coil made of a hollow ribbon of metal. »The coil winds or unwinds as its temperature changes. »This causes pressure changes in the coil. »The movement, is transmitted to a pointer which move on a scale. »It is similar to the bimetallic thermometer. C. Bourdon Gauge Thermometer »Consists of a coil made of a hollow ribbon of metal. »The coil winds or unwinds as its temperature changes. »This causes pressure changes in the coil. »The movement, is transmitted to a pointer which move on a scale. »It is similar to the bimetallic thermometer.

MEASUREMENT OF TEMPERATURE

2. Electric Thermometers »A. Thermocouple Principle: When a circuit made of two dissimilar metal wires has the two junctions maintained at different temperatures, an electromotive force is generated and a current will flow through the circuit. 2. Electric Thermometers »A. Thermocouple Principle: When a circuit made of two dissimilar metal wires has the two junctions maintained at different temperatures, an electromotive force is generated and a current will flow through the circuit.

MEASUREMENT OF TEMPERATURE »The current generated is proportional to the temperature gradient between the two junctions. »If one junction is maintained at a constant tempereture (cold junction), the other junction can be used as the actual thermometer (hot junction). »The current generated is proportional to the temperature gradient between the two junctions. »If one junction is maintained at a constant tempereture (cold junction), the other junction can be used as the actual thermometer (hot junction).

MEASUREMENT OF TEMPERATURE »The thermocoupe is made of a circuit of two dissimilar metal wires: 1-coopper 2- costantan. This combination is stable »The thermocoupe is made of a circuit of two dissimilar metal wires: 1-coopper 2- costantan. This combination is stable

MEASUREMENT OF TEMPERATURE »The cold junction is connected to a sensitive galvanometer calibrated in temperature units. » The reading obtained is a measure of the temperature of the hot junction. »The cold junction is connected to a sensitive galvanometer calibrated in temperature units. » The reading obtained is a measure of the temperature of the hot junction.

MEASUREMENT OF TEMPERATURE Advantages: 1. rapid response 2. reasonably accurate 3. measuring probe can be made in a small size Advantages: 1. rapid response 2. reasonably accurate 3. measuring probe can be made in a small size

MEASUREMENT OF TEMPERATURE B-Platinum Resistance Thermometer C-thermister thermometer B-Platinum Resistance Thermometer C-thermister thermometer

MEASUREMENT OF TEMPERATURE Sites of Body Temperature Measurement »Body temperature varies widely depending on the site of measurement. »esophageal temperature is thought to give the best guide to blood temperature. »Rectal temperature usually lags behind oesophageal temperature during surface cooling or warming »Nasopharyngeal temperature » the tympamic membrane temperature Sites of Body Temperature Measurement »Body temperature varies widely depending on the site of measurement. »esophageal temperature is thought to give the best guide to blood temperature. »Rectal temperature usually lags behind oesophageal temperature during surface cooling or warming »Nasopharyngeal temperature » the tympamic membrane temperature

REGULATION OF HUMIDITY IN OR DR.FATMA ALDAMMAS

A hygrometer is an instrument which measures the amount of water vapour contained in given sample of gas. A hygrometer is an instrument which measures the amount of water vapour contained in given sample of gas.

Measurement of Humidity 1. Regnault’s hygrometer: »a silver tube is cooled by evaporation of liquid ether. When the tube cools to the dew point of the surrounding air, a thin film of water will condense on the outside of the tube. »The temperature of ether is read on a thermometer when condensation is first observed » absolute humidity can be read from special tables or graphs. Measurement of Humidity 1. Regnault’s hygrometer: »a silver tube is cooled by evaporation of liquid ether. When the tube cools to the dew point of the surrounding air, a thin film of water will condense on the outside of the tube. »The temperature of ether is read on a thermometer when condensation is first observed » absolute humidity can be read from special tables or graphs.

Measurement of Humidity 2-Wet & dry bulb thermometers: »2 mercury—in—glass thermometers are mounted together side by side. » The bulb of one is exposed to the air, while that of the other is surrounded by a small wick which dips into a water reservoir. »The temp. of the wet bulb depends on the rate of evaporation, hence on the relative humidity of the surrounding air, and so it is lower than that of the dry bulb. 2-Wet & dry bulb thermometers: »2 mercury—in—glass thermometers are mounted together side by side. » The bulb of one is exposed to the air, while that of the other is surrounded by a small wick which dips into a water reservoir. »The temp. of the wet bulb depends on the rate of evaporation, hence on the relative humidity of the surrounding air, and so it is lower than that of the dry bulb.

Measurement of Humidity »If humidity is high, the rate of evaporation is less and the temp difference between the 2 bulbs is less. »Relative humidity s read from tables which relate the temp. of wet & dry bulbs of humidity. »If humidity is high, the rate of evaporation is less and the temp difference between the 2 bulbs is less. »Relative humidity s read from tables which relate the temp. of wet & dry bulbs of humidity.

Measurement of Humidity 3-Hair hygrometer: »based on the principle that human hair increases in length as the humidity of the surrounding air increases. »One end of the hair is fixed and the other end is attached to a very light lever system which magnifies the change in length. »Movement of the hair causes a pointer to move on a scale calibrated in percent relative humidity. »Hair hygrometers are commonly used In theater & baby incubators. 3-Hair hygrometer: »based on the principle that human hair increases in length as the humidity of the surrounding air increases. »One end of the hair is fixed and the other end is attached to a very light lever system which magnifies the change in length. »Movement of the hair causes a pointer to move on a scale calibrated in percent relative humidity. »Hair hygrometers are commonly used In theater & baby incubators.

Measurement of Humidity They are limited to the range between 15— 85% relative humidity, and the accuracy is not high.

Measurement of Humidity 4-Mass spectrometer: »can be used to measure water vapour pressure in gas mixtures, but its expense precludes its use for this purpose. 4-Mass spectrometer: »can be used to measure water vapour pressure in gas mixtures, but its expense precludes its use for this purpose.

Measurement of Humidity Importance of measurement of humidity in anaesthesia: »1. In operating theatres where a high relative humidity (above 50%) is maintained to decrease the risk of static sparks. »2. In patients on ventilators with endotracheal or tracheostomy tubes where extra humidity must be provided to prevent crusting of secretrers. Importance of measurement of humidity in anaesthesia: »1. In operating theatres where a high relative humidity (above 50%) is maintained to decrease the risk of static sparks. »2. In patients on ventilators with endotracheal or tracheostomy tubes where extra humidity must be provided to prevent crusting of secretrers.

REGULATION OF TEMP. ILLUMINATION & HUMIDITY IN OR