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

## TL;DR

This study measures how noninvasive ventilation affects airway resistance in healthy adults, showing that resistance increases with higher pressure settings.

## Contribution

The study introduces a novel method combining laryngoscopy and pressure measurements to quantify dynamic airway resistance during noninvasive ventilation.

## Key findings

- Upper airway resistance was significantly higher than translaryngeal resistance during both inspiration and expiration.
- Airway resistance increased with higher inspiratory positive airway pressure (IPAP) levels.
- Laryngoscopic observations aligned with the measured resistance changes during noninvasive ventilation.

## Abstract

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 (Ruaw) and translaryngeal (Rtl) resistance were calculated and compared with laryngoscopic findings. During IPAP10/EPAP4, the Ruaw was 4.25/4.21 and Rtl 2.20/3.45. During IPAP15/EPAP4, the Ruaw was 5.18/5.73, and the Rtl was 2.31/3.83. Ruaw was significantly higher than Rtl 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.

NIV modulates both upper airway and translaryngeal resistance. Our findings demonstrate that direct laryngoscopic observations align with the dynamic changes measured in resistance curves.