Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome

Am J Respir Crit Care Med. 1995 Jun;151(6):1807-14. doi: 10.1164/ajrccm.151.6.7767524.


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)

MeSH terms

  • Adult
  • Female
  • Humans
  • Lung / diagnostic imaging
  • Lung / physiopathology*
  • Male
  • Positive-Pressure Respiration* / adverse effects
  • Positive-Pressure Respiration* / methods
  • Pulmonary Gas Exchange / physiology
  • Respiratory Distress Syndrome / diagnostic imaging
  • Respiratory Distress Syndrome / physiopathology
  • Respiratory Distress Syndrome / therapy*
  • Tidal Volume / physiology*
  • Tomography, X-Ray Computed