Airway Clearance With an Optimized Mechanical Insufflation-Exsufflation Maneuver

Standard mechanical insufflation-exsufflation (MI-E) therapy is applied with fast insufflation-exsufflation pressures to achieve high peak expiratory flows (PEF) and assist airway clearance. No attention is given to the resultant high peak inspiratory flows (PIF), although it may impair secretion removal. It has been proposed that an expiratory flow bias (ie, PEF higher than PIF) might be the key determinant for mucus clearance instead of the PEF alone. We examined the effects of 2 MI-E maneuvers, standard versus optimized, with fast and slow insufflation, respectively, along with different MI-E pressure settings on secretion displacement in 3 lung-impedance scenarios that simulated a patient on mechanical ventilation. The MI-E device was connected to a lung model that simulated a patient on mechanical ventilation. Known quantities of mucus simulant were injected into the system and exposed to various MI-E ventilation conditions. Mucus movement was examined with image-analysis software. The optimized MI-E maneuver resulted in a much lower PIF (37.5 L/min [interquartile range, 24.9-47.9 L/min] vs 101.8 L/min [interquartile range, 89.1-115.7 L/min], < .001). Consequently, the expiratory flow bias, expressed by PEF:PIF and the PEF-PIF difference, was much higher in the optimized maneuver. The higher expiratory flow bias in the optimized maneuver displaced the mucus outward, with a difference of 2.6 cm compared with the standard maneuver. Multivariate analysis revealed that the type of maneuver (optimized vs standard), PEF-PIF difference and MI-E pressure gradient were significantly correlated with mucus displacement (r = 0.817, < .001), whereas the PEF was not. PEF:PIF and the PEF-PIF difference were lower in the obstructive lung scenario when compared with the restrictive and normal lung scenarios. The optimized MI-E maneuver, applied with slow insufflation, resulted in a higher expiratory flow bias, which made the therapy more effective at moving mucus outward, compared with the standard MI-E maneuver, typically applied with fast insufflation.