• Tiina M Andersen, Anne Kristine Brekka, Zoe Fretheim-Kelly, Manel Lujan, John-Helge Heimdal, Hege H Clemm, Thomas Halvorsen, Ove Fondenes, Roy M Nilsen, Ola D Røksund, and Maria Vollsæter.
• Thoracic Department, Haukeland University Hospital, Bergen, Norway; The Faculty of Health and Social Sciences, Western Norway University of Applied Science, Bergen, Norway. Electronic address: tiina.andersen@helse-bergen.no.
• Chest. 2024 Aug 26.

BackgroundMechanical insufflation-exsufflation (MI-E) uses positive and negative pressures to assist weak cough and to help clear airway secretions. Laryngeal visualization during MI-E has revealed that inappropriate upper airway responses can impede its efficacy. However, the dynamics of pressure transmission in the upper airways during MI-E are unclear, as are the relationships among anatomic structure, pressure, and airflow.Research QuestionCan airflow resistance through the upper airway and the larynx feasibly be calculated during MI-E, and if so, how are the pressures transmitted to the trachea?Study Design And MethodsCross-sectional study of 10 healthy adults with and without active cough to whom MI-E was provided, using pressure settings +20/-40 cm H2O and ± 40 cm H2O. Airflow and pressure at the level of the facemask were measured using a pneumotachograph, whereas pressure transducers (positioned via transnasal fiber-optic laryngoscopy) recorded pressures above the larynx and within the trachea. Upper airway resistance (Ruaw) and translaryngeal resistance (Rtl) were calculated (in centimeters of water per liter per second) and were compared with direct observations via laryngoscopy.ResultsPositive pressures reached the trachea effectively, whereas negative tracheal pressures during exsufflation were approximately half of the intended settings. Insufflation pressure increased slightly when passing through the larynx. Participant effort influenced tracheal pressures and the resistances, with findings consistent with laryngoscopic observations. During MI-E, resistance seems to be dynamic, with Ruaw exceeding Rtl. Inappropriate laryngeal closure increased Rtl during both positive and negative pressures.InterpretationRuaw and Rtl can be calculated feasibly during MI-E. The findings indicate different transmission dynamics for positive and negative pressures and that resistances are influenced by participant effort. The findings support using lower insufflation pressures and higher negative pressures in clinical practice.Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

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