Automatic recruitment maneuvers in porcine acute lung injury based on online PaO2 measurements
KeywordsAcute Lung Injury Fuzzy Controller Recruitment Maneuver Peep Level Protective Ventilation
The individualization of lung protective ventilation strategies (e.g. recruitment maneuvers [RM] and PEEP titration to keep the lungs open) requires careful bedside observations. Many parameters must be monitored, which calls for computer aid. A fuzzy-logic ventilation expert system has been tested regarding its ability to automatically conduct RMs based on the open lung concept (OLC).
The pulmonary parameters of one pig during an RM cycle can be seen in Fig. 1b. After 20 min, PaO2, Vt and compliance Crs (= Pdelta/Vt) were significantly increased in all animals and PaCO2 reduced to normal values. Phases 1–3 of the RM process lasted approximately 5 min, partially due to the dynamic latency (15 s) of the measurement system. An optimization of the fuzzy PaO2 controller and additional sensors will shorten the execution time and reduce the heart's pressure load. Figure 1c shows the CT and EIT images before and after RM. Atelectases are removed and ventilation is increased, more evenly distributed and shifted from ventral to dorsal regions.
Automatic RM with a sustained improvement of PaO2 and Crs could be achieved. The EIT showed a high potential to visualize and assess RM with a high temporal resolution.