Volume-pressure curve of the respiratory system predicts effects of PEEP in ARDS: "occlusion" versus "constant flow" technique

Am J Respir Crit Care Med. 1994 Jan;149(1):19-27. doi: 10.1164/ajrccm.149.1.8111581.

Abstract

The effects of positive end-expiratory pressure (PEEP) on static ("rapid airway occlusion" technique) and dynamic ("constant flow" technique) volume-pressure (V-P) curves were studied in 19 patients with adult respiratory distress syndrome (ARDS). To describe the shape of both curves, the nonlinear coefficient of a second-order polynomial equation fitted to the static (static nonlinear coefficient) and dynamic (dynamic nonlinear coefficient) V-P curves on zero end-expiratory pressure (ZEEP) was used. Two distinct patterns were observed: (1) in ten patients, the static and dynamic V-P curves on ZEEP exhibited a convex shape with a progressive decrease in slope with increasing inflation volume (nonlinear coefficients: negative). In these patients PEEP induced a volume displacement along the static and dynamic V-P curves on ZEEP (hyperinflation). (2) In nine patients, the static and dynamic V-P curves on ZEEP showed a concave shape with a progressive increase in slope with increasing volume (nonlinear coefficients: positive) and PEEP shifted both curves upward along the volume axis (alveolar recruitment). A correlation (p < 0.0001) between static and dynamic nonlinear coefficients was found at all levels of PEEP. Both static and dynamic nonlinear coefficients on ZEEP were correlated (p < 0.0001) with the amount of lung volume recruited with PEEP, and the variations of cardiac index (CI), O2 delivery (DO2), right-to-left venous admixture (Qs/Qt), and PaO2 with PEEP. Besides, the effects of PEEP on Cl, DO2, Qs/Qt, and PaO2 were less pronounced (p < 0.001) in patients with convex V-P curves than in patients with concave V-P curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Analysis of Variance
  • Blood Gas Analysis
  • Female
  • Hemodynamics*
  • Humans
  • Least-Squares Analysis
  • Lung Compliance
  • Male
  • Mathematics
  • Middle Aged
  • Positive-Pressure Respiration / methods*
  • Predictive Value of Tests
  • Pressure
  • Pulmonary Alveoli / physiopathology*
  • Pulmonary Gas Exchange
  • Residual Volume*
  • Respiratory Distress Syndrome, Adult / blood
  • Respiratory Distress Syndrome, Adult / mortality
  • Respiratory Distress Syndrome, Adult / physiopathology*
  • Respiratory Distress Syndrome, Adult / therapy*
  • Survival Rate