500 Section - Graphical Analysis of Mechanical Insufflation-Exsufflation flow waveforms under different pressure and interfaces

MI-E was administered to an 84-year-old male who underwent tracheostomy following off-pump coronary artery bypass grafting. Therapy consisted of five-cycle sets (inspiration 3s, expiration 2s, pause 2s), in eight pressure settings ranging from +30/−30 to +60/−60cmH₂O. The intervention was performed via tracheostomy cannula (with and without cuff inflation) over two days, followed by facial mask delivery for two additional days after decannulation. Real-time flow waveforms were captured via a gas flow analyzer and peak gas decompression spike (GDS) flow, peak expiratory flow (PEF) after GDS, and effective cough volume (ECV), peak inspiratory flow (PIF), and total inspired volume (TIV) were extracted.

Results:

Peak GDS flow increased with higher pressure settings across all interfaces. In the tracheostomy condition, both PEF and ECV increased proportionally with pressure. However, during facial mask application, maximal PEF occurred at +40/−50 cmH₂O and declined at higher pressures, with no clear pressure dependency for ECV. No significant differences were observed regarding cuff status. Notably, expiratory flow plateaued after the GDS in the tracheostomy condition, whereas a secondary flow rise was frequently observed with the facial mask, likely reflecting transient upper airway collapse and reopening.

Conclusion: MI-E flow characteristics and effective cough parameters differ significantly by interface. Therefore, interface-specific pressure titration is essential to optimize MI-E effectiveness.