As the available data testify, at many patients hypoxemic respiratory insufficiency at COVID-19 can differ from acute respiratory a distress syndrome in its more classical look (ARDS). Though in many cases considerable loss of residual volume is observed, the pulmonary extensibility (komplayns) at a considerable part of patients sufficiently remains at high degree of alveolar dead space that gives the grounds to assume damage of a reflex of hypoxemic pulmonary vasoconstriction or others, the mechanisms which are not investigated yet.
Due to the aforesaid, the following tactics at patients with the respiratory insufficiency caused by COVID-19 can be recommended.
1. Degree of oxygen insufficiency should be measured regularly by means of the S/F index (pulsoksimetriya indicators divided into fraction of oxygen in the inhaled air) (3–5). The S/F index is recommended for assessment of dynamics of a condition of the patient. It is not an invasive method, it can be applied to all patients, especially considering their large number. The coefficient of PaO2/FiO2 (P/F) is the gold standard of assessment of degree of oxygen insufficiency, but it can be reserved for maintaining patients in heavier by a state and hemodynamic instability (needing invasive methods of monitoring) or for S/F confirmation. It is important to teach medical personnel the correct technique of measurement of S/F, including titration of FiO2 for the purpose of achievement of a saturation at the level of 88–97%.
2. High-line therapy by oxygen (nasal cannula of a high stream of HFNC). High-line therapy by oxygen can be recommended at absence at patients of a heavy anoxemia, especially in case of deficiency of fans. However high-line therapy by oxygen is accompanied by the increased risk of creation a virus - the containing aerosols. Improvement in response to high-line therapy by oxygen should be estimated within 30–60 minutes after an initiation of treatment, in the absence of significant improvement it is necessary to stop the procedure. It is important to remember that high-line oxygenation does not provide significant increase in lung volume (8–10). If at the patient receiving high-line therapy by oxygen the moderate/heavy anoxemia is observed (S/F <220; FiO2> 0.4 for SpO2> 92%), we strongly recommend to consider transition to more intensive support of function of breath (noninvasive ventilation or an intubation), depending on existence of necessary resources. As for oxygen therapy by means of a mask with the tank, in view of features of this pathology it is necessary to exclude use of the similar device as it does not provide disclosure of lung volume. Besides, supply of oxygen in concentration of 100% increases PaO2 and SpO2 level, without improving at the same time P/F coefficient (the shunt, disclosure of lung volume) that can lead to delay with use of the adequate therapy directed to disclosure of lung volume. Therefore, it cannot serve as a substitute with CPAP at all.
3. Early use of CPAP/BLPAP (positive constant pressure in respiratory tracts / breath with two levels of positive pressure in respiratory tracts). Use of this technique should be considered in case of considerable need of the patient for oxygen or at considerable difficulties of breath. The response to CPAP/BLPAP should be estimated within 30 minutes after the beginning of therapy, in the absence of considerable improvement it is necessary to consider the possibility of an intubation if that is available. If at the patient who is on noninvasive ventilation the moderate/heavy anoxemia is observed (S/F <200; FiO2> 0.4), it is necessary to consider the possibility of an intubation if that is available. As the first line of treatment helmets masks, in the presence of those are recommended. For lack of helmets masks it is possible to use full-front masks though it demands use by personnel of means of protection in view of the raised aerozolization.
4. Intubation and transfer to IVL. In the presence of an opportunity, the patient should be intubated if after the beginning of noninvasive therapy at him P/F or S/F≤200 (FiO2> 0.4 remains). The patient who is on noninvasive ventilation or high-line oxygenation needs to be intubated at high rates of work of breath even if P/F or S/F> 200 (FiO2<0.4 для достижения SpO2> of 92%). For overcoming an anoxemia at IVL it is necessary to use a pron-position and maneuvers for disclosure of lung volume.
5. If the anoxemia is not overcome (P/F <150 or S/F <175) by means of a pron-position by the person and maneuvers for disclosure of lung volume, it is necessary to understand what type of damage of lungs is available: an acute respiratory distress syndrome with prevalence of change of a reflex of HPV or a classical acute respiratory distress syndrome. Further strategy will be defined by type of damage of lungs.