title: Volume-dependent compliance in ARDS: proposal of a new diagnostic concept.
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).
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Intensive care unit of a university hospital.
  
  
  METHODS
  14 ARDS patients, 2 patients with ALI.
  
  
  METHODS
  None.
  
  
  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.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, University of Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany. mols@ana1.ukl.uni-freiburg.de
authors.forename: G
authors.initials: G
authors.lastname: Mols
authors.forename: I
authors.initials: I
authors.lastname: Brandes
authors.forename: V
authors.initials: V
authors.lastname: Kessler
authors.forename: M
authors.initials: M
authors.lastname: Lichtwarck-Aschoff
authors.forename: T
authors.initials: T
authors.lastname: Loop
authors.forename: K
authors.initials: K
authors.lastname: Geiger
authors.forename: J
authors.initials: J
authors.lastname: Guttmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001784:Blood Gas Analysis; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D016014:Linear Models; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D015588:Observer Variation; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012128:Respiratory Distress Syndrome / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology* / Q000628:therapy; D013990:Tidal Volume