title: Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome.
abstract: The distribution of tidal volume (VT) and recruitment was investigated by chest computed tomography (CT) in eight sedated-paralyzed patients with the adult respiratory distress syndrome (ARDS). A CT section was obtained in the supine position at 0, 5, 10, 15, and 20 cm H2O positive end-expiratory pressure (PEEP) and at the corresponding inspiratory plateau pressure (21 +/- 1.8, 26 +/- 1.4, 31 +/- 1.8, 38 +/- 2.1, and 46 +/- 3.2 cm H2O [mean +/- SE]), keeping VT constant. Each CT section was divided along its ventral-dorsal height into 10 equally spaced intervals (levels). Vi(insp) and Vi(exp) were defined as the gas volume for level i (i = 1 to 10) at end-inspiration and at end-expiration, respectively. The following variables were computed at each lung level: (1) distribution of CT section tidal volume (VTct), i.e., the fraction of VT that inflates a given lung level; (2) the plateau-induced and PEEP-induced recruitment, i.e., the amount of lung tissue previously collapsed that inflates at plateau pressure and at PEEP, respectively; (3) the reopening-collapsing tissue, i.e., the amount of lung tissue that regains inflation at plateau pressure and collapses at PEEP. With increasing PEEP from 0 to 20 cm H2O, the VTct distribution decreased significantly (p < 0.01) in the upper levels, did not change in the middle levels, and increased significantly (p < 0.01) in the lower levels.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Istituto di Anestesia e Rianimazione, IRCCS Universitá degli Studi di Milano, Ospedale Maggiore, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Gattinoni
authors.forename: P
authors.initials: P
authors.lastname: Pelosi
authors.forename: S
authors.initials: S
authors.lastname: Crotti
authors.forename: F
authors.initials: F
authors.lastname: Valenza
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012128:Respiratory Distress Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D013990:Tidal Volume / Q000502:physiology*; D014057:Tomography, X-Ray Computed