Realistic glottal motion and airflow rate during human breathing

• The glottal motion during breathing was examined on 20 subjects using laryngofibroscopy and synchronized oral airflow measurements.
• Two groups were sorted out: a “static” group, gathering subjects with a constant glottal area during the breathing cycle; a “dynamic” group, gathering subjects with a time-varying glottal area.
• A correlation motion related to the airflow dynamics was found during inspiration.
• The realistic breathing mode (mobile glottis, non-sinusoidal flow rate) was shown to be an energy saving maneuver compared to an idealized mode (steady glottis, sinusoidal flow rate).

The glottal geometry is a key factor in the aerosol delivery efficiency for treatment of lung diseases. However, while glottal vibrations were extensively studied during human phonation, the realistic glottal motion during breathing is poorly understood. Therefore, most current studies assume an idealized steady glottis in the context of respiratory dynamics, and thus neglect the flow unsteadiness related to this motion. This is particularly important to assess the aerosol transport mechanisms in upper airways.This article presents a clinical study conducted on 20 volunteers, to examine the realistic glottal motion during several breathing tasks. Nasofibroscopy was used to investigate the glottal geometrical variations simultaneously with accurate airflow rate measurements. In total, 144 breathing sequences of 30s were recorded.Regarding the whole database, two cases of glottal time-variations were found: “static” or “dynamic” ones. Typically, the peak value of glottal area during slow breathing narrowed from 217 ± 54 mm2 (mean ± STD) during inspiration, to 178 ± 35 mm2 during expiration. Considering flow unsteadiness, it is shown that the harmonic approximation of the airflow rate underevaluates the inertial effects as compared to realistic patterns, especially at the onset of the breathing cycle. These measurements provide input data to conduct realistic numerical simulations of laryngeal airflow and particle deposition.