Purpose: The purpose of this study is to describe and test a modified Boussignac system for non-invasive continuous positive airway pressure, aimed at reducing the decrease in inspiratory oxygen fraction (FiO(2)) with higher inspiratory peak flow rates.
Methods: We modified a Boussignac circuit by inserting a T-piece between the Boussignac valve and the face mask. The T-piece was connected to a reservoir balloon receiving oxygen by an independent source. The system was tested in a bench study, consisting of five steps, with increasing inspiratory peak flow rates (V(insp)) Three levels of PEEP were tested: 7, 10 and 13 cmH(2)O. The following devices were tested: Boussignac, Boussignac with reservoir but without supplementary oxygen, Boussignac with reservoir and 10 (SUPER-Boussignac(10)) and 30 l/min (SUPER-Boussignac(30)) of supplementary oxygen. In each step we measured FiO(2), tidal volumes, and airway pressure.
Results: FiO(2) increased with PEEP and decreased at increasing V(insp) with all the systems. However, FiO(2) increased with SUPER-Boussignac(10) (7-10%) and with SUPER-Boussignac(30) (10-30%). Moreover, in the latter case, for V(insp) values up to 60 l/min, FiO(2) became independent of V(insp). The SUPER-Boussignac allowed also smaller drop in airway pressure during inspiration and higher tidal volumes.
Conclusions: The SUPER-Boussignac represents a simple way to significantly improve the performance of the Boussignac device.