The present study was undertaken to assess the feasibility of an integrated approach that combines direct laryngoscopy and measuring airflow and pressures throughout the upper airway and the larynx during MI-E cycles. We aimed to assess how MI-E pressures reach the trachea and to calculate airflow resistance at different anatomical levels, specifically from the mask to the larynx and then through the larynx to the trachea (translaryngeally). The overarching objective was to acquire knowledge that enhances the effectiveness, tolerance, and safety of MI-E in patient care.
This was a cross-sectional study of ten healthy adults, where MI-E was provided with and without active cough, employing pressure settings +20/-40 and ±40 cmH2O. Airflow and pressure at the level of the facemask were measured using a pneumotachograph, while pressure transducers (positioned via transnasal fiberoptic laryngoscopy) recorded pressures above the larynx and within the trachea. Upper airway resistance (Ruaw) and translaryngeal resistance (Rtl) were calculated (cmH2O/L/sec) and compared to direct observations via laryngoscopy.
The positive insufflation pressures remained relatively stable throughout the upper airway and trachea, providing the larynx remained open. In contrast, the negative exsufflation pressures decreased and were less negative in the trachea compared to the facemask, indicating a significant absorption of negative pressures by the upper airway above the larynx during exsufflation. The Ruaw was higher than the Rtl, especially during exsufflation, indicating that the upper airway plays a significant role in the conveyance of pressure during MI-E. Laryngeal adduction, observed during both insufflation and exsufflation, increased Rtl, highlighting the impact of laryngeal function on airflow resistance during MI-E. These dynamic resistances reflected the movements as they were observed laryngoscopically and were clearly influenced by the participants’ effort.
Upper airway and translaryngeal resistance can feasibly be calculated 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.
The findings deepen our understanding of how airway pressures induced by MI-E propagate dynamically through different sections of the upper airway, larynx, and trachea, as well as how resistance is distributed prior to exerting therapeutic effects in the lungs.
mechanical insufflation-exsufflation
mechanically assisted cough
