Intraoperative PEEP selection by pressure-based capnography: a proof of concept study.

PURPOSE

We aimed to test a new method to determine the positive-end expiratory pressure (PEEP) that maintains the lungs open after a recruitment maneuver (RM).

METHODS

In eleven anesthetized patients, we compared the standard RM searching for the optimal PEEP based on the highest respiratory compliance (PEEP), with a new method. This method performs a RM during a slow pressure-volume curve and detects the optimal PEEP using the novel barometric capnography curve (BCap); i.e. the plot of expired carbon dioxide versus airway pressure. The lungs' closing pressure was detected when the slope of phase III of the BCap changed along this slow expiration (PEEP). The main objective was to compare PEEP with the reference PEEP. As a secondary objective, we explored the association between PEEP and the polarity change in end-expiratory transpulmonary pressure (PEEP) during the deflation phase of a slow flow PV curve.

RESULTS

We found a PEEP of 8.5(3.3) cmHO that was no statistically different from the PEEP of 10.0(4.0) cmHO (p = 0.72). Both methods correlated well with a Rho of 0.84 (p < 0.001). The Bland-Altman plot showed a bias of 0.19 and LOA of 1.92 cmHO (95%CI -0.39 to 0.77 cmHO). During the PV slow deflation limb, PEEP was 9.3(4.3), which was statistically similar to PEEP (p = 0.61). Both pressures were strongly correlated (Rho = 0.93, p < 0.001) with a bias of -0.3 cmHO and LOA of 1.52 (95%CI -0.76 to 0.16 cmHO).

CONCLUSIONS

We concluded that BCap is feasible to detect lungs collapse using a constant flow PV curve.