ARDSnet Ventilatory Protocol and Alveolar Hyperinflation: Role of Positive End-Expiratory Pressure

Am J Respir Crit Care Med. 2007 Oct 15;176(8):761-7. doi: 10.1164/rccm.200702-193OC. Epub 2007 Jul 26.

Abstract

Rationale: In patients with acute respiratory distress syndrome (ARDS), a focal distribution of loss of aeration in lung computed tomography predicts low potential for alveolar recruitment and susceptibility to alveolar hyperinflation with high levels of positive end-expiratory pressure (PEEP).

Objectives: We tested the hypothesis that, in this cohort of patients, the table-based PEEP setting criteria of the National Heart, Lung, and Blood Institute's ARDS Network (ARDSnet) low tidal volume ventilatory protocol could induce tidal alveolar hyperinflation.

Methods: In 15 patients, physiologic parameters and plasma inflammatory mediators were measured during two ventilatory strategies, applied randomly: the ARDSnet and the stress index strategy. The latter used the same ARDSnet ventilatory pattern except for the PEEP level, which was adjusted based on the stress index, a monitoring tool intended to quantify tidal alveolar hyperinflation and/or recruiting/derecruiting that occurs during constant-flow ventilation, on a breath-by-breath basis.

Measurements and main results: In all patients, the stress index revealed alveolar hyperinflation during application of the ARDSnet strategy, and consequently, PEEP was significantly decreased (P < 0.01) to normalize the stress index value. Static lung elastance (P = 0.01), plasma concentrations of interleukin-6 (P < 0.01), interleukin-8 (P = 0.031), and soluble tumor necrosis factor receptor I (P = 0.013) were significantly lower during the stress index as compared with the ARDSnet strategy-guided ventilation.

Conclusions: Alveolar hyperinflation in patients with focal ARDS ventilated with the ARDSnet protocol is attenuated by a physiologic approach to PEEP setting based on the stress index measurement.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Cardiac Output / physiology
  • Cohort Studies
  • Female
  • Humans
  • Interleukin-6 / blood
  • Interleukin-8 / blood
  • Male
  • Middle Aged
  • Positive-Pressure Respiration / methods*
  • Pulmonary Alveoli / physiopathology*
  • Pulmonary Gas Exchange / physiology
  • Receptors, Tumor Necrosis Factor, Type I / blood
  • Respiratory Distress Syndrome, Adult / physiopathology*
  • Respiratory Distress Syndrome, Adult / therapy
  • Respiratory Mechanics / physiology
  • Tidal Volume / physiology
  • Vascular Resistance / physiology

Substances

  • Interleukin-6
  • Interleukin-8
  • Receptors, Tumor Necrosis Factor, Type I