Influence of microclimate on a human organism

Microclimate basically affects the thermoregulation system of a human organism.

Thermoregulation systemofa human organismmay be of 2 types: chemical (heat production) and physical (heat emission), in a healthy person they are in a dynamic balance.

System of Thermoregulation

It consists of chemical thermoregulation Q1 (thermogenesis) and physical thermoregulation Q2 (heat emission). Q1 = Q2

System of Thermoregulation

Chemical Thermoregulation (Thermogenesis)	Physical Thermoregulation (Heat Emission):
	1. Heat conduction (30-40 %)
	2. Heat evaporation (10-15 %)
	3. Heat radiation (40-45 %).

Chemical Thermoregulation (Thermogenesis)

This is heat formation in the body due to biochemical processes, its level being determined by the basal metabolism. In a healthy person the level of heat production basically depends on air temperature (Т)* (through thermoreceptors in the skin and centers of thermoregulation in CNS). A zone of indifference has the temperature of 15-25º С. If the temperature is below 15 ºС, the increase of heat production takes place, if above 25 º С — the decrease of heat production; at over 35 ºС there may be disturbance of thermoregulation (thermal fatigue, thermal feet edema, thermal emaciation, heat cramps, heat shock, thermal syncope).

Physical Thermoregulation (Heat Emission)

There are three ways of heat emission:

v Heat conduction (30-40 %)

Ø Convection — emission of heat to the air (it depends on Т, Е, V)*.

Ø Conduction — emission of heat to objects (it depends on Т of object, its thermal conductivity and area of contact with an object).

v Heat evaporation (10-15 %) — it occurs on perspiration and depends on Т, Е, V of the air.

v Heat radiation (40-45 %). It depends on radiation temperature, i.e. the difference between temperature of environmental objects and a body temperature (36.6 ºC).

_____________________________________________________________________

*Note: Т — temperature, Е — humidity, V — speed of air movement

In normal conditions (in rest) a person loses 30 % of heat due to heat conduction, 15 % — heat evaporation and 55 % — heat radiation.

Types of Thermoregulation Disturbance in Hot Climate

These include thermal emaciation, thermal hypostases of legs, thermal emaciation due to dehydration and desalination on perspiration, heat spasms, heatstroke, thermal fainting. (See Theme No 25 in the end of the textbook).

 

Table 25

Standards of Microclimate for Different Premises and Methods of its Estimation

Factor of microclimate	Kind of premise	Norms
Temperature of air Devices: thermometers, thermograph	Habitable rooms Sports halls Operating-rooms	18-22˚С 16-18˚С 22-25˚С
Air humidity Devices: psychrometer, hygrometer	Habitable rooms Operating-rooms	40-60 % up to 55%
Speed of air movement Devices: anemometer, catathermometer	Habitable rooms Child institutions	0.2-0.4 m/sec 0.07-0.1 m/sec

Air Temperature

The optimal temperature range for any premises (rooms) is 18-22ºС, for sports halls — 16-18˚С, for operating-rooms — 23-25°С (prevention of postoperative complications from cold are necessary, because in patient under narcosis the centers of thermoregulation do not work).

 

Fig. 9. Instruments and methods of taking air temperature

 

The instruments for taking air temperature are called thermometers.

Thermometers may be: household, minimal and maximal.

Thehouseholdthermometer shows temperature at the given moment, it does not fix the temperature.

The minimalthermometer fixes the lowest temperature for a certain period. The minimal thermometers have a capillary with alcohol inside.

Themaximalthermometer fixes the highest temperature for a certain period. The maximal thermometers have a capillary with hydrargyrum inside. The medical thermometers are maximal thermometers.

Rules for Taking Air Temperature in a Room

· Taking air temperature horizontally.

The temperature of air is taken at a height of 1.5 meters above floor level in five points. The first, second, third, fourth points are the four corners of a room. The fifth point is in the centre of a room. The odds between measurements of air temperature in these points should be not more than 2º С.

· Taking air temperature vertically.

The temperature of air is taken in the centre of a room at a height of 0.1 meter above floor level (at a level of man’s feet) and 1.5 meters above floor level (at a level of man’s respiratory organs). The odds between measurements of air temperature in these points should be not more than 2.5º С.

· Taking air temperature within a day.

· The temperature is taken in a room in the morning, afternoon, evening and night. The odds between these measurements should be not more than 5º С at local heating (fireplaces, furnace). The odds between these measurements should be not more than 3º С at central heating (radiators of central heating).

 

Fig. 10. Thermograph

 

The purpose of this device is determination and recording of fluctuations of air temperature within time.

Design and principle of its work:

· A perceiving part — a temperature sensor: it presents a bent bimetallic plate consisting of 2 metals having various temperature coefficients. At fluctuations of temperature the radius of plate curvature changes, that is transferred to the pointer with the help of lever system including the driving mechanism — lever, rod, regulator, axis.

· A recording part: the pointer, which has a writing point on one end, registering on a tape having an hour and day scale of temperature changes.

· Drum with an hour mechanism. The tape is reeled up on a rotating drum; the drum can make a complete revolution for one day (daily) or for one week (weekly).

Thermograph provides continuous registration of air temperature in a range of +45 - -55º С with accuracy of ±1º.

Humidity of Air

The following types of humidity are distinguished:

· Absolute — the amount of water vapours in the air at a given moment (g/m3 or mm/Hg);

· Maximal — the greatest possible saturation of air with water vapours at a given temperature,

· Relative = absolute/maximal in %.

The norm of air humidity is 40-60 % (30-70 %); at a lower humidity dryness of skin and mucous membranes are observed, at a higher humidity the disturbance of heat emission takes place. In operating-rooms the humidity should be not more than 55 % in order to prevent the explosion of ether-air mixture).