Effects of Mechanical Insufflation-Exsufflation With Different Pressure Settings on Respiratory Mucus Displacement During Invasive Ventilation

Abstract

Background: Mechanical insufflation-exsufflation (MI-E) has been proposed as a potential strategy to generate high expiratory flows and simulate cough in the critically ill. However, efficacy and safety of MI-E during invasive mechanical ventilation are still to be fully elucidated. This study in intubated and mechanically ventilated pigs aimed to evaluate the effects of 8 combinations of insufflation-exsufflation pressures during MI-E on mucus displacement, respiratory flows, as well as respiratory mechanics and hemodynamics.

Methods: Six healthy Landrace-Large White female pigs were orotracheally intubated, anesthetized, and invasively ventilated for up to 72 h. Eight combinations of insufflation-exsufflation pressures (+40/-40, +40/-50, +40/-60, +40/-70, +50/-40, +50/-50, +50/-60, +50/-70 cm H₂O) were applied in a randomized order. The MI-E device was set to automatic mode, medium inspiratory flow, and an inspiratory-expiratory time 3 and 2 s, respectively, with a 1-s pause between cycles. We performed 4 series of 5 insufflation-exsufflation cycles for each combination of pressures. Velocity and direction of movement of a mucus simulant containing radio-opaque markers were assessed through sequential lateral fluoroscopic images of the trachea. We also evaluated respiratory flows, respiratory mechanics, and hemodynamics before, during, and after each combination of pressures.

Results: In 3 of the animals, experiments were conducted twice; and for the remaining 3, they were conducted once. In comparison to baseline mucus movement (2.85 ± 2.06 mm/min), all insufflation-exsufflation pressure combinations significantly increased mucus velocity (P = .01). Particularly, +40/-70 cm H₂O was the most effective combination, increasing mucus movement velocity by up to 4.8-fold (P < .001). Insufflation pressure of +50 cm H₂O resulted in higher peak inspiratory flows (P = .004) and inspiratory transpulmonary pressure (P < .001) than +40 cm H₂O.

Conclusions: MI-E appeared to be an efficient strategy to improve mucus displacement during invasive ventilation, particularly when set at +40/-70 cm H₂O. No safety concerns were identified although a transient significant increase of transpulmonary pressure was observed.

Keywords: ICU; mechanical insufflation-exsufflation; mechanical ventilation; mucus displacement; respiratory mechanics; respiratory physiotherapy.