[Dynamics of pressure and flow curves of various expiratory pressure valves]. / Dynamik von Druck- und Flusskurven verschiedener Auslassventile.

ABSTRACT

BACKGROUND: Flow dynamics of exhalation valves in home care ventilators (CPAP-, BiLevel-, and autoadjust machines) are determined by their physical properties. The flow characteristic implies distinct curves leading to expiratory increase and inspiratory decay of pressure depending on flow rate. MATERIAL AND METHODS: For examination of pressure/flow characteristic we examined several valves (one and two circular holes, Sullivan-, Whisper-Swivel-, Silence-valve). Expiratory peak and inspiratory trough assessed at constant pressure (10 mbar) were measured with varying flow rates. RESULTS: Valves differ with their pressure characteristics up to 1.2 mbar for inspiratory and 1.0 mbar for expiratory flow at 2.0 1/s. CONCLUSION: The specific characteristic for each valve is part of the total efficiency of a home care ventilator. Their pressure flow relationship has to be taken into account for titration process and for exchange between different machines and accessories.