Volumetric Сapnography As a Tool for Evaluation of Alveolar Ventilation Effectiveness in Clinical Practice
The purpose of the study was to compare the relationship between the dead space volume and tidal volume (VD/VT) using volumetric capnography (VCap) during pressure controlled (PCV) and pressure supported (PSV) ventilation mode in the postoperative period.Materials and methods. 30 randomly assigned cardiac surgical patients undergoing CABG (coronary artery bypass grafting) using ECC (extracorporeal circuit) were included in an observational, prospective study. Patients were connected to the ventilator immediately after ICU admission. After that, monitoring VD/VT, CO2 production (VECO2) as well as ventilation parameters was carried out. The parameters during PCV and PSV mode were statistically evaluated using t-test.Results. Expiratory CO2 (ETCO2) concentration were not significantly different in both PCV or PSV (p=NS), although both VECO2 and minute ventilation (MV) increased during PSV mode (p<0.01). VD/VT in PSV mode was lower than in PCV. Gas exchange represented by alveolar ventilation (VA) was better during PSV (p<0.01). VA was also higher during PSV (p<0.05). The calculated VD/VT ratio differed between PCV and PSV mode (p<0.01).Conclusion. VCap represents a tool for monitoring of CO2 exchange effectivness. We registered a decrease in VD/VT with improved alveolar ventilation (VA) in PSV mode. VCap seems to be a suitable instrument for adjustment of protective lung ventilation.