Respiratory and non-respiratory airflow characteristics across ingestive and non-ingestive swallowing tasks

Respiratory-swallowing coordination is critical for safe swallowing. Respiratory phase patterns, indicating the direction of respiration bracketing swallowing, appear minimally altered when oral airflow is measured alongside nasal airflow. Measures from an oronasal facemask also demonstrate broader features of swallowing non-respiratory flow (SNRF) associated with the respiratory-swallowing pause than previously reported. Additionally, nasal and oronasal flow estimates show variability in within-individual respiratory phase patterning. In this study, an oronasal facemask and separate nasal-only mask were used to assess healthy individuals, exploring how instrumentation influences respiratory phase pattern estimates across swallowing tasks. Characteristics of SNRF and variability of respiratory phase patterns were also investigated. Adding oral flow to nasal flow appeared to reduce estimated exhale-swallow-exhale patterning by 13% and increased the estimated frequency of alternative patterns, although this may include some genuine variance between the datasets due to asynchronous data acquisition from each mask. SNRF occurred in 87-97% of swallows, with inward and outward flow occurring at the onset and offset of the respiratory-swallowing pause. Test-retest reliability of respiratory phase patterns within individuals ranged from κ = 0.4 - 0.54, with ≥2 patterns observed across four trials >40% of the time. Findings suggest that adding oral to nasal flow alters estimates of respiratory phase patterns, particularly during ingestive swallowing tasks. SNRF is observed more frequently when measured through a closed system, presenting as inwardly- or outwardly-directed airflow at the beginning or end of the respiratory-swallowing pause. Finally, there appears to be considerable variability in respiratory phase patterning across trials of the same swallowing condition.