Impact of high- and low-flow nebulised saline on airway hydration and mucociliary transport.

Background: Nebulised drugs, including osmotic agents and saline, are increasingly used during noninvasive respiratory support, including nasal high-flow therapy. The authors conducted an Methods: In a perfused organ bath, 10 sheep tracheas were exposed to 7.5 mL nebulised 0.9% and 7.0% saline entrained into heated (38°C) and humidified air delivered at high and low flow (20 and 7 L·min Results: The airway surface liquid height increased significantly with both 0.9% and 7.0% saline: at low-flow by 37.2±10.0 µm and 152.7±10.9 µm, respectively, and at high-flow by 62.3±5.6 µm and 163.4±25.4 µm, respectively (p<0.001). Mucus velocity was increased by both 0.9% and 7.0% saline from a baseline of 8.2±0.8 mm·min Conclusions: The findings demonstrate that nebulised isotonic 0.9% saline, like hypertonic 7.0% saline, significantly stimulates basal mucociliary transport, and the use of high-flow delivery had no significantly different hydration effects compared with low-flow delivery. Hypertonic 7.0% saline suppressed ciliary beating, indicating an increase in airway surface liquid osmolarity, which may have negative effects on the airway surface with frequent use.