Different particle flow from exhaled air after gradual increase of PEEP during mechanical ventilation

Abstract Objectives: Detecting particle flow from the airways by none invasively online analysing technique might serve as an additional tool to monitor mechanical ventilation. In the present study we used a customised Pexa (Particles in Exhaled Air), which is an optical particle counter for airway monitoring of particle flow in exhaled air. Positive end expiratory pressure (PEEP) is often used as a tool during recruitment manoeuvre and the aim of this study was to investigate the impact of different levels of PEEP on particle flow in exhaled in an experimental setting.Methods: Five animals received a gradual increase of 5 PEEP to a maximum of 25 PEEP during VCV. Measurements were done before every increase in PEEP in fully anaesthetised domestic pigs. The particle count along with vital parameters and ventilator settings were collected continuously. The particle sizes measured was between 0.41 µm and 4.55 µm.Results: All animals had a significant increase in particle count going from all increased levels of PEEP and back down to baseline PEEP of 5 cmH2O. Here shown with PEEP 15 that had a mean particle count of 401 ± 122 particles compared to after release of PEEP back to 5 with a mean particle count of 5968 ± 1784 (p<0.001). A significant decrease was seen in blood pressure in the higher levels of PEEP compared to PEEP 5 cmH2O.Conclusions: In the present study significant increase in particle count was seen when releasing PEEP back to baseline compared to all levels of PEEP. This finding may indicate that this technique can give diagnostic possibilities for monitoring lung function during mechanical ventilation.