Upper airway and translaryngeal resistance during mechanical insufflation-exsufflation

<bold>Background:</bold> Mechanical insufflation-exsufflation (MI-E) use positive and negative pressures to assist weak cough. Laryngeal visualization during MI-E has highlighted that inappropriate upper airway responses can impede efficacy. The dynamics of pressure transmission in the upper airways during MI-E is unclear, as are the relationships between anatomical structure and airflow. <bold>Objectives:</bold> To assess feasibility of calculating resistance during MI-E, evaluate resistance across the upper airway, and elucidate the pressures reaching the trachea. <bold>Methods:</bold> Ten healthy adults performed MI-E sessions with and without active cough, with pressure settings of +20/-40 and ±40 cmH₂O. A pneumotachograph was used to measure airflow and pressure in the facemask, whereas pressure transducers, positioned via transnasal fiberoptic laryngoscopy, recorded pressures above the larynx and within the trachea. Upper airway resistance (R_uaw) and translaryngeal resistance (R_tl) were calculated (cmH₂O/L/sec) and compared to the visual images. <bold>Results:</bold> Positive pressures reach the trachea effectively, while negative pressures in the trachea were approximately half of the settings. Insufflation pressure increased slightly when passing through the larynx. Participant effort influenced pressures and resistance, with findings consistent with laryngoscopic observations. During MI-E, resistance appears dynamic, with R_uaw exceeding R_tl. Inappropriate laryngeal closure increased R_tl. <bold>Conclusions:</bold> Calculating resistance in the upper airways during MI-E is feasible. The upper airway absorbs significant parts of the negative pressure during exsufflation. The findings may prove clinically significant for optimizing MI-E pressure settings.