Abstract
There is no consensus neither literature nor constructor to define inspiratory rise time (Tmpi) which is equally called “pressure ramp slope” or “pressurization rate”. The purpose of this study was to evaluate on a test bench the Tmpi of four home ventilators, versus different resistances.
SMARTAIR ST (Airox), TRILOGY100 (Respironics), VIVO40 (Breas, GE) and VPAPIII (Resmed) were tested in a bilevel pressure support mode. All Tmpi available were tested. Simulations were performed on an ASL 5000 (Ingmar Medical, Pittsburgh, USA) which simulates normal and obstructive lung. Tmpi has been defined as the delay between return to EPAP (Expiratory Positive Airway Pressure) after begin of inspiratory effort and time where pressure reaches 90% of maximal pressure. For each setting versus resistance, value of Tmpi and slope of “pressure and flow” curves in their linear segment were calculated.
Only Tmpi of VPAPIII and TRILOGY100 don't vary according to resistances. However, values measured are always above than specified, particularly TRILOGY100. Tmpi measured for SMARTAIR ST and VIVO40 decrease when resistances increase. Pulmonary dynamics can explain this results. In order to control this Tmpi, four strategies are observed. Resmed uses a fixed pressure slope, whereas Breas set a fixed flow slope. SMARTAIR maintain a fixed pressure slope until a preset time (300ms), after what slope vary versus resistance. Lastly, curve's TRILOGY is an exponential. This ventilator seems to maintain a fixed time constant on the pressure curve.
We prove that ventilators have different strategies to achieve targeted maximal pressure. This is a first step in elaboration of standardized test lung protocols to compare ventilators.
- © 2011 ERS
