(E55) Tolerance of Binasal Prongs for Delivery of Non-invasive Ventilation to Foals

Abstract:

Background: Non-invasive ventilation (NIV) is a method of providing respiratory support without the need for airway intubation. NIV can be delivered by helmet, mask or nasal prongs. To date, studies in foals have used mask delivery, but the mask is poorly tolerated and associated with hypercapnia, possibly associated with the accumulation of carbon dioxide within equipment dead space and/or with expiratory flow limitations.

Objectives: This study was conducted to evaluate the tolerance of prototype binasal prongs (Figure 1) in healthy unsedated foals, and following light sedation. Animals Six healthy foals, < 1 week old.

Methods: Observational behavior study with NIV delivered at incremental pressures. Tolerance of binasal prongs was assessed using an ethogram to document behavior in unsedated foals, and subsequently following light sedation (diazepam 5mg IV). Thereafter, foals were subjected to NIV at incremental pressure support and peak end-expiratory pressure for sequential two-minute intervals. Results All foals tolerated NIV through binasal prongs, although increasing airway pressures were associated with increased inspiratory volume, duration of inspiration and air leakage in most foals. These changes preceded discontinuation / intolerance of NIV on the basis of behaviour changes consistent with discomfort. Increased circuit leakage was associated with reduced return of expired air to the ventilator and increasing disparity between inspiratory and expiratory times and tidal volumes. Conclusions and clinical importance: Binasal prongs were well tolerated and might be suitable for NIV, but design and fitting require further optimization. Behavior and ventilator variables should be monitored to predict patient tolerance of NIV.