Tidal Hyperinflation During Low Tidal Volume Ventilation in Acute Respiratory Distress Syndrome

Am J Respir Crit Care Med. 2007 Jan 15;175(2):160-6. doi: 10.1164/rccm.200607-915OC. Epub 2006 Oct 12.

Abstract

Rationale: Tidal volume and plateau pressure limitation decreases mortality in acute respiratory distress syndrome. Computed tomography demonstrated a small, normally aerated compartment on the top of poorly aerated and nonaerated compartments that may be hyperinflated by tidal inflation.

Objectives: We hypothesized that despite tidal volume and plateau pressure limitation, patients with a larger nonaerated compartment are exposed to tidal hyperinflation of the normally aerated compartment.

Measurements and main results: Pulmonary computed tomography at end-expiration and end-inspiration was obtained in 30 patients ventilated with a low tidal volume (6 ml/kg predicted body weight). Cluster analysis identified 20 patients in whom tidal inflation occurred largely in the normally aerated compartment (69.9 +/- 6.9%; "more protected"), and 10 patients in whom tidal inflation occurred largely within the hyperinflated compartments (63.0 +/- 12.7%; "less protected"). The nonaerated compartment was smaller and the normally aerated compartment was larger in the more protected patients than in the less protected patients (p = 0.01). Pulmonary cytokines were lower in the more protected patients than in the less protected patients (p < 0.05). Ventilator-free days were 7 +/- 8 and 1 +/- 2 d in the more protected and less protected patients, respectively (p = 0.01). Plateau pressure ranged between 25 and 26 cm H(2)O in the more protected patients and between 28 and 30 cm H(2)O in the less protected patients (p = 0.006).

Conclusions: Limiting tidal volume to 6 ml/kg predicted body weight and plateau pressure to 30 cm H(2)O may not be sufficient in patients characterized by a larger nonaerated compartment.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Female
  • Humans
  • Lung / diagnostic imaging
  • Male
  • Middle Aged
  • Respiration, Artificial / methods*
  • Respiration, Artificial / standards*
  • Respiratory Distress Syndrome, Adult / diagnostic imaging
  • Respiratory Distress Syndrome, Adult / therapy*
  • Tidal Volume
  • Tomography, X-Ray Computed