Late-breaking abstract: Bi-level positive airway pressure (Bipap) effects on regional distribution of lung ventilation in COPD

Aim: To assess changes on distribution of lung ventilation before and after Bipap, in patients (pts) with chronic respiratory failure (CRF) due to severe COPD. Methods: 11 COPD pts (mean age 69.3±7.5), in stable conditions, underwent two successive ventilation scans (V) with a radiolabeled aerosol (99mTc nanocolloid albumin,Venticoll, GE). The first ventilation was done using FAI device (Fasteras, MPR), and the second one using an adapted nasal mask system (FA2), which allows evaluation of (V) distribution after Bipap. Clinical symptoms and arterial blood gas analysis were observed before and after treatment. The images of (V) before and after Bipap were quantified by a semi-automatic procedure which divides each lung in 3 regions of interest (ROI): upper, medium and lower lung field, to obtain the upper/lower (U/L) ratio. An automatic iso-level ROI procedure enabled radioactivity measurement (counts) of ventilated area (Va 5% and 30%), on the right posterior and on the right lateral lung. A ventilation distribution inhomogeneity index (INI) was defined as the ratio count/pixels, calculated on isoROI 5% and 30% (INI 5 and 30%). Results: A significant reduction of U/L ratio (F=12.12; p Conclusions: A significant improvement of the physiologic gradient (U/L), an increment of ventilated areas (Va 5%,30%), and a reduction of regional ventilation inhomogeneity distribution (INI) are likely underlying the therapeutic effect of the Bipap in COPD.