title: Analysis of nonlinear volume-dependent respiratory system mechanics in pediatric patients.
abstract: OBJECTIVE
  Analysis of dynamic respiratory system mechanics is generally based on a resistance-compliance model in which nonlinearities of the respiratory mechanics indices are not considered. The recently developed SLICE method analyzing consecutive volume slices of the tidal volume was used for determination of non-linear volume-dependent respiratory system mechanics. Volume-dependent compliance C(Slice) and resistance R(Slice) were compared with C(MLR) and R(MLR) obtained by standard multiple linear regression analysis (MLR).
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Pediatric intensive care unit in a university hospital.
  
  
  METHODS
  Fifteen pediatric patients, aged 24 days to 9.6 yrs, weighing 3-67.5 kg.
  
  
  METHODS
  None.
  
  
  RESULTS
  With respect to their pulmonary status, the patients were grouped into three clinical groups: patients with no lung diseases, patients with restrictive lung diseases, and patients with obstructive lung diseases. All patients were mechanically ventilated via a cuffed endotracheal tube in the pressure-controlled mode. Flow and airway pressure were measured at the proximal end of the tube and tracheal pressure was continuously calculated. Respiratory mechanics were determined either with the SLICE method or, as reference, by using standard MLR. In most patients, the pressure-volume relationship was nonlinear, particularly in patients with restrictive and obstructive lung diseases. In the presence of considerable nonlinearity, the volume-dependent respiratory mechanics indices obtained by the SLICE method showed better agreement between recalculated and original pressure-volume loops compared with the MLR results. Furthermore, signs of overdistension of the patient's lung became obvious when using the SLICE method, whereas they were undetected by MLR.
  
  
  CONCLUSIONS
  The SLICE method is well suited for the analysis of nonlinear volume-dependent respiratory system mechanics in pediatric patients. The SLICE method may be used as a first step toward an adaptation of ventilator settings with respect to the actual mechanical status of the patient's respiratory system, and, to prevent pulmonary overdistension.
authors.affiliation: Section of Experimental Anesthesiology, Department of Anesthesiology and Critical Care Medicine, University of Freiburg, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Kessler
authors.forename: C J
authors.initials: CJ
authors.lastname: Newth
authors.forename: J
authors.initials: J
authors.lastname: Guttmann