Exploring upper airway and laryngeal resistance to noninvasive ventilation in healthy awake adults

The interaction between anatomical structures, pressure, and airflow impacts the airway resistance. The airflow during noninvasive ventilation (NIV) relies on the upper airway and laryngeal patency. This study aimed to quantify the airflow resistance at these levels during NIV. In this cross-sectional study examining 10 healthy, awake adults, we established a NIV setup incorporating a continuous video-recorded transnasal laryngoscopy and simultaneous airway pressure measurement using a transducer positioned above and below the vocal folds. Airflow and mask pressure were recorded by a pneumotachograph at the mask. NIV was delivered with inspiratory positive pressure (IPAP)/expiratory positive pressure (EPAP) set to 10/4 and 15/4 cmH₂O. Upper airway (R_uaw) and translaryngeal (R_tl) resistance were calculated and compared with laryngoscopic findings. During IPAP10/EPAP4, the R_uaw was 4.25/4.21 and R_tl 2.20/3.45. During IPAP15/EPAP4, the R_uaw was 5.18/5.73, and the R_tl was 2.31/3.83. R_uaw was significantly higher than R_tl for inspiration at both IPAP levels (p = 0.001 and p = 0.012), and for expiration with IPAP15/EPAP4 (p = 0.048). The resistance appeared dynamic during the NIV cycle, and the findings aligned with the laryngoscopic observations. NIV modulates upper airway and translaryngeal resistance. Resistance increases with elevated IPAP levels, particularly within the upper airway.