Volume-dependent Compliance in ARDS: Proposal of a New Diagnostic Concept

Intensive Care Med. 1999 Oct;25(10):1084-91. doi: 10.1007/s001340051016.

Abstract

Objective: Adaptation of ventilator settings to the individual's respiratory system mechanics requires information about the pressure-volume relationship and the change of compliance which is dependent on inflated volume. Unfortunately, established methods of obtaining this information are invasive and time-consuming, and, therefore, not well suited for clinical routine. We propose a new standardized diagnostic concept based on the recently developed slice method. This multiple linear regression method (MLR) determines volume-dependent respiratory system compliance (C(SLICE)) within the tidal volume (V(T)) during ongoing mechanical ventilation. The impact of a ventilator strategy, recommended by a consensus conference, on the course of compliance within V(T) was investigated in patients with the acute respiratory distress syndrome (ARDS) or acute lung injury (ALI).

Design: Prospective observational study.

Setting: Intensive care unit of a university hospital.

Patients: 14 ARDS patients, 2 patients with ALI.

Interventions: None.

Measurements and results: After measurement of flow and airway pressure and calculation of tracheal pressure, C(SLICE) was determined. The resulting course of C(SLICE) within V(T) was estimated using a mathematical algorithm. C(SLICE) data were compared to those obtained by standard MLR. We found decreasing C(SLICE) mainly in the upper part of V(T) in all patients. In 7 patients, we found an additional increasing C(SLICE) mainly in the lower part of V(T).

Conclusions: C(SLICE) was not constant in patients with ARDS/ALI whose lungs were ventilated according to consensus conference recommendations. The proposed diagnostic concept may serve as a new tool to obtain a standardized estimation of respiratory system compliance within V(T) non-invasively without interfering with ongoing mechanical ventilation.

MeSH terms

  • Adolescent
  • Adult
  • Algorithms
  • Blood Gas Analysis
  • Diagnosis, Computer-Assisted / methods*
  • Female
  • Humans
  • Linear Models
  • Lung Compliance*
  • Male
  • Middle Aged
  • Monitoring, Physiologic / methods*
  • Observer Variation
  • Positive-Pressure Respiration / methods*
  • Prospective Studies
  • Reproducibility of Results
  • Respiratory Distress Syndrome, Adult / diagnosis*
  • Respiratory Distress Syndrome, Adult / etiology
  • Respiratory Distress Syndrome, Adult / metabolism
  • Respiratory Distress Syndrome, Adult / physiopathology*
  • Respiratory Distress Syndrome, Adult / therapy
  • Tidal Volume*