RESUMO
Clinical and physiological effects of pressure-regulated ventilation of the lungs using the inverse rate of inhalation to exhalation (PCV-IR) were studied in two groups of patients. No appreciable advantages of this mode of pulmonary ventilation in comparison with common ("volumic") method were observed in group 1 patients (following open-heart surgery) with moderately expressed respiratory disorders (PaO2/FIO2 = 340c13 and index of lung comprometation 0.7c0.04). At the same time, the level of the peak inhalation pressure in the airways at PCV-IR was reliably lower than during common artificial ventilation of the lungs (AVL). In patients with grave respiratory disturbances (PaO2/FIO2 = 93c10 and index of lung comprometation 6.88c0.56) application of this scheme brought about an improvement of pulmonary biomechanics and gas exchange, but the hemodynamics was virtually the same. It is noteworthy that the process of PCV-IR adaptation required a thorough preliminary "adjustment" of the ventilation parameters and took rather a long time in the majority of patients. Positive effects of PCV-IR may be due to several mechanisms: a slowing down (ramp-like) flow, limitation of the upper pressure during inhalation, prolongation of exhalation in comparison with inhalation, and a regulated level of internal positive end expiratory pressure. PCV-IR is recommended as a variant of respiratory support in the treatment of patients with severe involvement of the lungs, when the potentialities of common AVL are exhausted.
