Clinical evaluation of diminished early expiratory flow (DEEF) ventilation in mechanically ventilated COPD patients
To evaluate the cardiopulmonary effects, especially the end-expiratory lung volume (EEV) and ventilation inhomogeneity during diminished early expiratory flow ventilation (DEEF), which resembles pursed-lips breathing, with the conventional intermitent positive pressure ventilation (IPPV) in postoperative mechanically ventilated patients with chronic obstructive pulmonary disease (COPD). A prospective study measuring cardiopulmonary parameters during IPPV, DEEF, and positive end-expiratory pressure (PEEP) as a control mode. In the PEEP mode, PEEP values were chosen such that the mean airway pressure during a breath cycle was equal to that during the DEEF mode, which was higher than the conventional IPPV mode. Surgical intensive care unit of a university hospital. 20 postoperative mechanically ventilated COPD patients who were optimally pretreated and had normal blood oxygenation. Measurements were started in the IPPV (IPPV1) mode, continued in a randomized order with DEEF or PEEP, and completed with a second IPPV (IPPV2) mode, with 1 h equilibration time in each mode before each measurement. A multi-breath indicator gas wash-out test was used to calculate the EEV and ventilation inhomogeneity. There was a 9% increase (p<0.05) in the mean EEV during both the DEEF and PEEP mode compared to IPPV. No significant changes in the ventilation inhomogeneity and deadspace fractions or the hemodynamic parameters were found during the different ventilatory modes. There was no improvement in pulmonary and hemodynamic parameters during the DEEF mode in comparison to the IPPV mode. The small increase in EEV during DEEF was probably caused by the slightly higher mean expiratory pressures as in the PEEP mode. However, this had no effect on the hemodynamic parameters. As we could not observe any improvement with the DEEF ventilation in our optimally pretreated postoperative COPD patients, we do not advise applying this therapy in this group of patients, since this mode of ventilation may cause barotrauma if not monitored adequately.