Constant positive pressure at the end of an exhalation represents an IVL mode option when which using in an expiratory phase it is created and supported certain, predetermined by the doctor, the level of positive pressure. It allows not to reduce pressure in a rebreathing system to zero and to realize positive pressure in respiratory tracts during all respiratory cycle.
It is very difficult to overestimate value of positive pressure at the end of an exhalation. Creation of positive pressure during all hardware respiratory cycle allows to support alveoluses in the straightened state, protecting them from falling off. Besides, positive pressure in a rebreathing system allows to improve oxygenation of the patient considerably.
It is necessary to notice that the healthy person who breathes through natural respiratory tracts also has mechanisms which are responsible for maintenance of alveoluses in the straightened state and creating constant positive pressure in respiratory tracts during all respiratory cycle. In particular, it is provided with a half-closed condition of a glottis. At introduction to respiratory tracts of the patient of a tube (intubation or tracheostomy) operation of this mechanism stops, respiratory tracts of the patient become completely open and so-called physiological PDKV is leveled.
Therefore use of positive pressure at the end of an exhalation is important even at patients without pulmonary pathology, for example, when carrying out the general anesthesia with IVL, when transporting with IVL and so on. But it is of particular importance at patients with different types of damage of lungs, and in particular, at a koronavirusny infection.
Actually, constant positive pressure at the end of an exhalation is used at treatment of patients with acute respiratory a distress syndrome for a long time. Considering that damage of lungs at a koronavirusny infection often has similarity to ORDS, use of the similar principles of respiratory therapy is possible. The purposes of use of positive pressure at the end of an exhalation at ORDS the following:
reduction of the pulmonary shunt by recruitment and disclosure of alveoluses and redistribution extravasated ̆ liquids in lungs;
maintenance of alveoluses in the straightened state after recruitment in the conditions of ventilation with a low respiratory volume;
restriction of cycles of opening/closing of alveoluses (prevention of an atelektotravma).
At the same time constant positive pressure at the end of an exhalation is more effective and safer at a diffusion otek of lungs (uniform ̆ recruitment), than at focal defeat, especially with primary damage of back lower parts (restretching of upper parts of lungs without effective recruitment is possible).
It is necessary to use selection of constant positive pressure at the end of an exhalation. It is reached by gradual increase in positive pressure in respiratory tracts before increase in Rao2 at the smallest FiO2 value, limited inspiratory pressure of Pin and control of venous return (monitoring of warm emission is desirable).
Control of a hemodynamics when using constant positive pressure at the end of an exhalation is important very much as this option leads to growth of intrathoracic pressure and, as a result, to decrease in venous return. If the patient is initially compromised on a condition of a cardiovascular system (for example, has not filled hypovolemia), then use of PDKV is capable to lead to considerable disturbances of a hemodynamics. At the same time what the value of positive pressure at the end of a breath will be higher, especially expressed will be hemodynamic disturbances.
Use of PDKV when carrying out so-called alveolar recruitment is of also great importance. This reception has wide use at treatment respiratory a distress syndrome. The essence of a method consists that with rather safe inspiratory pressure in respiratory tracts less than 30 cm vodn. articles can open still ̈ capable to ventilation and the alveoluses which are not completely fallen down. For the purpose of involvement in ventilation of the greatest possible number of alveoluses apply manevr "opening of lungs" (recruitment, mobilization) alveoluses.
Manevr of recruitment represents temporary increase in pressure and/or volume in respiratory tracts for the purpose of opening of kollabirovanny alveoluses with dalneishy maintenance them in a patency during all respiratory cycle by means of constant positive pressure at the end of an exhalation. Recruitment at initially low PDKV and low respiratory volume is of particular importance. Also it is used for fight against falling off of alveoluses after carrying out sanitation of respiratory tracts.