Spread of a koronavirusny infection created serious load of intensive care units and an intensive care just because of needs of such patients in serious respiratory support which in certain cases can include artificial ventilation of the lungs. In this article we will deal with whether it is possible to use for mechanical ventilation of patients with a koronavirusny infection the ventilation modes with control on volume.
It should be noted that carrying out ventilation with control on volume at patients with rather intact pulmonary tissue and normal resistance of airways in a number of situations quite reasonably and does not cause great difficulties in specialists. It is connected with the fact that lungs in such situation represent so-called single-component model: pulmonary fabric is rather uniform, the majority of alveoluses finish synchronously and evenly, without making significant mechanical impact at each other. Therefore the mode of volume ventilation is often applied, say, in the operating room. Its undoubted advantages is that are guaranteed the set respiratory volume, minute ventilation and adequate elimination of carbon dioxide. But also in addition to the operating room, at observance of the above-stated conditions (intact pulmonary tissue and normal resistance of airways), the ventilation mode with control on volume can be used. In literature cases of long-term volume IVL are described, in particular, at pathology of the central nervous system.
On the other hand, ventilation by excessive volumes causes significant decrease in pliability of lungs due to development of collapse of alveoluses eventually. At the same time the developing clinical picture is very similar to the acute respiratory distress syndrome (ARDS), that is it is possible to speak about approach of restrictive pathology of lungs owing to ventilation.
When we speak about ventilation on the volume of patients with restrictive pathology of lungs to which ORDS caused by a koronavirusny infection belongs (in those clinical options when decrease in extensibility of pulmonary fabric takes place), we have absolutely other situation. It is known that such pathology of lungs is characterized their parenchyma expressed by heterogeneity when more struck departments (alveoluses) adjoin to less struck or even normal (healthy) pulmonary fabric and respiratory tracts. In such situation lungs represent two-component model — a row located the struck and intact zones of lungs.
What occurs if we try to ventilate such patient with control on volume? The respiratory volume which is forcibly given by the fan comes mainly on a line of least resistance, that is to less affected, intact part of lungs that leads to the fact that the most part of respiratory volume is the share of these departments. Intact pulmonary fabric pererastyagivatsya, pressure considerably increases in it that finally leads to a barotrauma with the subsequent destruction of surfactant. Another, the part of lungs patholologically changed is ventilated badly that leads to progressing in these sites of collapse of alveoluses, to an atelektazirovaniye and disturbance of gas exchange. Finally, such ventilation leads to further deterioration ventilating and perfusion the relation ̆ and to blood shunting aggravation from right to left.
The second downside of ventilation on volume is that pressure in hyper - and the hypoventilated zones of lungs considerably differs among themselves and logically that it will be much higher in the reinflated departments. When these zones adjoin with each other, owing to a gradient pressure ̆ between them there are stretching forces when more pliable alveoluses stretch and press on less pliable. And these forces can be very big therefore there is a damage of walls of alveoluses and intersticial space, ruptures of small vessels to the subsequent hemorrhages in a parenchyma of lungs. Finally we get a barotrauma and a volyumotravma of lungs.
Thus, remain the main scopes of mechanical ventilation of the lungs with control on volume short-term postoperative IVL, IVL at intact lungs (respiratory insufficiency owing to the central or neuromuscular reasons), short IVL at obstructive pathology of lungs. Use of this mode of mechanical ventilation at a koronavirusny infection is not recommended for the reasons which were stated above.