Method for modeling hypoxia with hypercapnia in animals

FIELD: medicine, experimental physiology.

SUBSTANCE: hypoxia with hypercapnia should be modeled due to creating a closed system of inhaled air circulation. Air enters lungs out of hermetically sealed reservoir and at expiration returns back. The process of recirculation is supplied with an apparatus of artificial pulmonary ventilation. The innovation suggested provides steadiness in development of hypoxia with hypercapnia excluding the development of stressor reaction. Conditions should be created to carry out any manipulations with an animal in the course of an experiment.

EFFECT: higher efficiency of modeling.

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The invention relates to the field of experimental physiology. The model can be applied to study the dynamics of indicators characterizing the status of the experimental animal in the development of acute and subacute hypoxia with hypercapnia.

There is a method of modeling the state of hypoxia with hypercapnia in mice used for screening of chemicals with the aim of finding new antihypoxants. The experimental animal is placed in a sealed glass jar standard capacity (250 ml). The mouse in the course of the experiment consume some of the oxygen, replacing it with an equivalent amount of carbon dioxide. The method allows to monitor the behavior of the animal, to record the frequency of respiratory movements, as well as to fix the main parameter is the duration of life (criterion of death is the moment of complete respiratory arrest). (Novikov V.E., Katunin I.E. the Study of antihypoxic properties of new derivatives of 3-oksipiridina // West. Smolensk honey. Academy. - 2002. No. 3. - P.9-10).

The main drawback of the model is the inability to check the many options of life and limiting effects on the body during the experience (the use of irritants, the introduction of medicinal substances) without breaching system.

To overcome these weeks the mistakes some researchers use the method of cyclic alternating periods of asphyxia with periods of recovery. The breath of an animal (usually a cat) is switched to the mode of artificial ventilation (respiratory muscles off muscle). Asphyxia is achieved by briefly stopping the artificial lung ventilation (ALV). The period of asphyxia replace the recovery period, i.e. including the ventilator. Then the cycle repeats. (V.M. Vinogradov, Krivoruchko B. I. Pharmacological brain protection from hypoxia //Psychopharmacology and biological narcology. 2001. - T.1. - C.27-37).

Shortcoming is the inability to create conditions for a smooth, gradual deterioration of the gas environment, without sharp fluctuations. Our studies showed that resistance to hypoxia in animals when using this model largely depends on the degree of activation of the sympathoadrenal system and its response to stress. Often the immediate cause of death in the experiment with asphyxia is not a gas imbalance in the body, and the sudden development of heart failure in response to stress.

The essence of the proposed method simulation of hypoxia with hypercapnia is that by connecting the animal to an artificial lung ventilation (ALV), create a closed volume of circulating air, including the system IVL-tight tank of a given size using two tubes, through one of which the air is from the tank through the ventilator is blown into the lungs of the animal, the second is returned into the tank during exhalation.

This method of modeling hypoxia with hypercapnia provides standardization of the initial conditions and a gradual deterioration in the quality of the inhaled air, and also allows the experimenter to perform hardware control over the development of hypoxia and make pharmacokineti at any stage of hypoxia.

The method of modeling hypoxia with hypercapnia is as follows. Hold stereotyped operations: animal anesthesia (5% solution calypsol intraperitoneally); tracheostomy and intubation of the T-shaped glass tube (the tube is hermetically fixed in the trachea ligature); shut down the respiratory muscles through the introduction of muscle relaxants (1% solution of d-tubocurarine) with the transfer of the animal on a ventilator.

The ventilator is connected tight tank required volume (figure 1). Into it enter the ends of the two PVC tubes. The tube 1 is attached to the input 2 (taking the air) fitting the ventilator 3. The air from the tank 4 is delivered into the lungs of the animal 5.

Another tube 6 is attached to the output end of the tracheal T-tube 7. The exhaled air is collected in the tank 4, which provides the recycling process air mixture. Deep breath (tidal volume) is adjusted using a special sliding for the ima 8, who feature on the tube 6 near the output end of the endotracheal tube 7.

The method allows the determination of the gas volume in the vessel using any gas analyzer by connecting it to the tube 1 (or through an additional tube, previously introduced into the container 4). In our experiments we used the analyzer carbon dioxide chemical (AUCH-2).

Example:

Cat (male) weight 4.2 kg were narcoticyou 5% solution of calypsol (2.5 ml intraperitoneally). After tracheostomy, intubation of the T-shaped tube and insertion of a muscle relaxant (1% solution d-tubocurarine 3 ml intramuscularly) was replaced with self-breathing animal artificial lung ventilation (ALV).

Recorded electrocardiogram (ECG) by counting the number of heart rate (HR); electroencephalogram (EEG); measured rectal temperature electric thermometer.

For registration of evoked potentials (EP) annoying electrodes were applied to the sciatic nerve of the right hind paws. Stimulation was performed with a separate rectangular pulses of constant current: amplitude - 40×10³mV; duration is 20 MS. A drain electrode disposed on the surface of the skull: active in the field of cortical somatosensory projection zones of the right hind legs (the left hemisphere of the brain); zero the electrode m is waiting for the frontal sinuses.

Assessment activity KGM animal was carried out by the method of registration of the EAP. Comparing the amplitude of the waves of the primary and secondary responses and duration of interval indicators (latent period, the duration of the first positive, the first negative and second positive waves).

Figure 2 shows the background (control) EAP registered with a cat 5 hours after anesthesia by kalipsola (i.e. after termination of anesthesia) immediately before connecting to the recirculation system.

After connecting the animal to the recirculation system after 30 minutes form the EAP begins to change (Fig.3-5).

Figure 3 shows the EAP through 35 minutes after connecting. The amplitude of the negative wave of the primary response is reduced by almost 2 times.

Figure 4 shows that after 45 minutes the secondary response disappears. Is the expansion of the initial response by lengthening the negative waves.

After 50 minutes the EAP is not registered (figure 5).

Heart rate during the experiment was gradually increased from 180 beats per minute up to 228.

Rectal temperature decreased from 37.5°C to 37.0°C.

The proposed method of modeling hypoxia with winarcadia used in experiments on 12 cats with the study of the dynamics of evoked potentials and the activity of single neurons in the cerebral cortex.

Thus, the new mod is l allows you to explore a large number of parameters of the body and to avoid sudden manifestations of the stress response in connection with the gradual development of hypoxia, that ensures the stability of the responses and prevents sudden death of animals associated with the development of heart failure.

The method of modeling hypoxia with hypercapnia the animal by means of its connection to an artificial lung ventilation (ALV), characterized in that create a closed volume of circulating air, before connecting inlet of the ventilator tight tank with two tubes, through one of which the air from the tank through the ventilator is blown into the lungs of the animal, and through the second returns to the tank during exhalation.