Body temperature at the person is maintained at the constant level and it is distinctive feature of gomoyotermny (hematothermal) organisms. The newborn child, even healthy full-term, in the first week of life, is poikilothermic, i.e. his temperature depends on ambient temperature. Normal level of axillary temperature at newborn 36.5-37.5 °C (WHO, 1997). To support this thermal range creation of the teromoneytralny environment when consumption of oxygen and power consumption are minimum for maintenance of vital activity on condition of preservation of normal body temperature is necessary.
The temperature balance in a human body is regulated by processes of heat production and a thermolysis which balance is under control of a hypothalamus. Newborns have an unripe hypothalamic system. About relative maturing of central office of thermal control it is possible to judge by establishment of the correct circadian rhythm of body temperature (usually to 1.5-2-month age). At premature children this process can be dragged out for indefinite time. The acute and chronic hypoxia, a birth trauma, neonatal infections and other morbid conditions not only slow down maturing process, but also can be the cause of gross violations in work of the center of thermal control with oppression of the set-point function of a hypothalamus, up to his temporary paralysis.
The answer of an organism to a hypothermia are: increase in heat production, reduction of a thermolysis and strengthening of muscular work (fever). It should be noted that the last defense reaction is not characteristic of newborn children, and reduction of their physical activity owing to hard swaddling makes them even more vulnerable in respect of a hypothermia.
Heat in a human body is formed as a result of biochemical oxidation reactions of glucose and fats. In case of lack of receipt from the outside and decrease in endogenous reserves of these nutrients, for the purpose of formation of energy and heat begin to be used proteins that leads to delay of growth and development of the child. Scientists said about it more than a century ago: "In view of the fact that babies badly adapt to the environment, it is necessary to avoid at them any, even temporary cooling. If it occurred, then a consequence is not only temperature drop of a body, but also a stop or even decrease of weight, t.e we see that at disbolism first of all the body gain stops". (B.Balge, 1912).
The main endogenous sources of heat in an organism of the child are brown fat and a glycogen. At the person brown fatty tissue is well developed only at newborns (about 5% of body weight) and is in the region of a neck, kidneys, along an upper back, on shoulders. Also in an organism of babies brown fatty tissue often meets in the look mixed with white fatty tissue. For newborns brown fatty tissue has unique value, helping to avoid a heavy hypothermia at the birth. The glycogen begins to collect in a fruit liver in the last trimester of pregnancy. At the birth a glycogen stock at the newborn child in 5 times more concerning body weight, than at the adult. But in two hours the level of a glycogen decreases by 90%, and in 6 hours in a liver only its traces and restoration of a stock of a glycogen are found in the healthy full-term newborn child to adult norm occurs only by the end of the first week of life.
Processes of biochemical oxidation of nutrients happen in the presence of oxygen. When cooling the child its oxygen requirement increases by 1 °C three times.
There are two physiological ways of reduction of a thermolysis: vasoconstriction and conscious reduction of the open space of a body surface. It is clear, that the last way is not possible in a case with the newborn child without assistance. Vasoconstriction — defense reaction of an organism which has the negative consequences, such as decrease in a renal and mezenterialny blood-groove, increase in a tone of pulmonary vessels. Losses of heat come from a human body on an internal and external gradient. Anatomo-fiziologichesky features of the newborn child: thin, well vaskulyarizirovanny skin, poorly developed hypodermic and fatty layer, rather big surface area of a body promote increase in losses of heat. There are several mechanisms of losses of heat. Radiation (loss is warm in space) — low air temperature in the delivery room, chamber, an incubator. A conduction (loss is warm at contact with cold objects) — diapers, a table, scales, hands. Convection (loss is warm with air flow) — a draft, cold air in the couveuse, ventilation of the lungs by cold oxygen air mixture. Evaporation — moist skin of the child, dry air in the couveuse, undamped oxygen air mixture.
Temperature in a body and in a cavity of the uterus has relatively a constant — about 38 °C. The fruit which is in a uterus irrespective of the term of a gestation has temperature slightly 0.3-0.5 °C above. Sharp cooling of the child at the birth from 38.0 °C to 35.0 °C — makes physiological sense, being one of the main mechanisms of stimulation of the first breath. At the same time the speed of decrease in body temperature is 0.4 °C/min. It is proved that the naked newborn child in the environment with a temperature of 23 °C suffers from loss of heat the same as the naked adult at a temperature of 0 °C!
Therefore if not to take a measure to warming of the newborn, body temperature can decrease to catastrophically low figures and to become a proximate cause of death of the child.
There is a list of the actions directed to prevention and treatment of a hypothermia confirmed with practice and data of evidential medicine. The concept of "a thermal chain" offered by World Health Organization represents the sequence of the interconnected procedures reducing the probability of development of a hypothermia and promoting good adaptation of the child to new living conditions.
The thermal chain consists of several links:
increase in readiness of personnel (all health workers, have to understand importance of maintenance of normal body temperature of the newborn, have the corresponding preparation on monitoring of a state and control of temperature of the baby);
creation of optimum temperature condition for the newborn (air temperature in the delivery room is not below 24.0 °C, inclusion of a lamp of radiant heat in 30 min. prior to childbirth, warming of a set of the linen intended for the child);
immediate obsushivaniye of the been born child a warm diaper, immediate change of a damp diaper with dry;
vykladyvaniye of the child covered with a dry diaper on mother's breast;
early applying of the child to a maternal breast;
resuscitation has to be carried out on a warm surface under a source of radiant heat;
transportation in warm conditions; to warm the child his transportation is expected so far; during the translation indoors to use contact — "skin to skin";
corresponding swaddling of the child;
joint stay of mother and child.
High-quality protection against heatlosses in the delivery room is provided by lamps of radiant heat as a part of open resuscitation circuits. For premature children additional resources of thermoprotection are used: transparent packages, a film from heat-resistant plastic, knitted hats and socks. Creation of temperature comfort and thermal protection remain relevant vposleduyushchy at all stages of nursing of newborn children.
The efficiency of a radiant energy provided with a source of radiant heat depends on many variable factors and technology features of ORS:
sources of thermal infrared radiation;
quantity and power of heating elements;
various levels of a thermocycle (fluctuation of temperature of the child);
range of infrared radiation;
design and diameter of a reflector (reflector);
possibilities of adjustment of intensity of radiant heat;
distance between the heated element and matrasiky;
the sizes and form of the warmed-up bed (bed).
Specialists need to know features of heating and a thermocycle of the ORS various heating elements, local and general heating of a bed, to use own laying and arrangement of the child on matrasika that it did not overheat, received warmly evenly, without the expressed gradient of temperatures or did not cool down. Considering that in ORS with radiant heat it is impossible to take precisely ambient temperature, always has to be qualitative servokontrol temperatures of skin of the child and the alarm system on a case of involuntary detachment of a temperature sensor. In the ORS modern models for the purpose of bigger safety and the best efficiency the following options are entered: adjustment of distance between a bed and a heating element with automatic correction of a radiation intensity, temperature sensors matrasika / a bed with servokontroly, the additional functions limiting overheating or unstable work of these systems.
For creation of temperature comfort by the sick and premature newborn incubators are widely used. Considering the modern requirements imposed to couveuses it is expedient to divide them into several classes taking into account design features and range of opportunities.
Basic incubators have the simple heating system and moistening — a standard fan heater (hair dryer) for forcing and recirculation of the heated filtered room air with the fixed flow rate via the built-in tank with water (humidifier). The system of moistening passive, depends on many variables and usually does not exceed 60%. Walls of incubators in the majority of models unary. The air flow rate in caps can reach 0.9 m/s, creating "effect of wind" that can increase losses of heat with evaporation and convection. The majority of couveuses of this group reckon servokontrol air temperatures, in some – servokontrol skin temperatures from one thermistor. System of the alarm system the elementary, unregulated.
Incubators for an intensive care and leaving have microprocessor attemperation of air and the child and work of all systems of the device. The important feature of servokontroliruyemy incubators is automatic cooling of the couveuse at temperature increase of skin of the child (from a skin thermistor). In case the child has a feverish state caused by infectious process it can complicate diagnostics. If the child has an expressed thermolability, then adjustment of heating of the couveuse on temperature of skin can lead to the expressed temperature differences and inadvertently cause temperature and metabolic destabilization of the child. In such cases gains special importance double servokontrol temperatures. The system of moistening in these incubators active with servokontroly humidity. Walls of caps double. Is available expanded multilevel the systems of the sound and visual alarm. In many couveuses there is a possibility of inclusion of additional upgrade: increase in range of heating of air, oxygen concentration monitoring, etc.
High-class incubators are intended for long and safe intensive nursing of premature and sick newborns, including treatment of twins. The principle of work that is convective heating. Cap walls double. The air flow rate over a bed does not exceed 0.1 m/s. There is more perfect system of heating and moistening. These incubators differ in the lowest noise level from operation of units that is of particular importance when nursing children with very low and extremely low body weight. Is available multilevel adjustment and control of key parameters about a possibility of maintenance of the stablest ambient temperature and skin of the child, humidity and oxygen concentration in a couveuse cap "is thin". System of moistening active. In some incubators humidifiers are taken out in separate remotely-controlled blocks with the built-in bactericidal filters. In a standarny complete set there are two channels of thermometry - the central and peripheral skin sensors, servokontrol air temperatures, humidity, oxygen concentration and a trendsistema on several monitoring indicators. Additional options are: the warmed-up antidecubital matrasik, the warmed-up regiments for accessories, the built-in electronic scales, the systems of phototherapy, additional monitoring of vital functions.
The transforming incubators combining functions of the closed convective incubators and open resuscitation circuits with radiant heat which on today's are, perhaps, the best systems of an intensive care and nursing for children with ONMT and ENMT belong to the same class.
To additional resources of thermal protection matrasik treat with heating which are widely used at care of newborns. They represent various (porolonovy, gel, foam, water, air) electric systems with adjustment of temperature of all bed or places of contact with the child's trunk. In many researches it is noted that such matrasik at isolated use without other means of a heat-shielding cannot betray sufficient heat to the child. Therefore use of such systems is possible at thermostable children at constant ambient temperature and demands obligatory swaddling, clothing and use of blankets.
The thermal mapping of the premature children who are when nursing in incubators or ORS, which is carried out in several researches in clinics of the USA and Italy showed that there is a direct dependence of temperature reaction of the child on temperature of hands of medical personnel during contact. Quite often after such contacts not only the general temperature status changes, but also there are negativy cardiovascular reactions. Therefore it is always necessary to remember that temperature reaction of the newborn depends also on such trifle as warm hands. Certainly, what would not be the technician "clever", the most reliable and safe source of heat for the child is his mother. Close corporal contact – "skin-to-skin" in difference from other methods of warming will never lead to overheating, and the effect of "impriting" allows to come into close mental and neuroendocrinal contact, forming the adequate psychological and somatic status of the child.
Thus, maintenance of normal body temperature for newborns has vital value. And the impossibility of ensuring temperature comfort and thermal protection can "nullify" efficiency of any hi-tech methods of treatment.