title: The volume dependence of stress relaxation in the rat respiratory system.
abstract: OBJECTIVE
  To investigate the volume dependence of respiratory system stress relaxation in anesthetized, positive-pressure ventilated rats.
  
  
  METHODS
  The effects on respiratory system stress relaxation of changing the end inflation volume while keeping tidal volume constant, and of changing the tidal volume while maintaining constant end inflation volume, were separately studied by the end-inflation occlusion method. These changes were obtained by inflating the respiratory system starting from different volumes above functional residual capacity.
  
  
  RESULTS
  We found that: (1) a simple exponential equation well describe the visco-elastic pressure drop for different inflation modalities; (2) the stress relaxation-linked, visco-elastic pressure drop, increases with increasing the tidal volume and keeping the end-inflation volume constant, but is independent from the end-inflation lung volume at constant tidal volumes; (3) time constant values show a significant increment with end-inflation volume at constant tidal volume but result independent from tidal volume variation at constant end-inflation volume.
  
  
  CONCLUSIONS
  Stress relaxation-linked pressure dissipation increases with increasing tidal volume independently from end-inspiratory volume.
authors.affiliation: 1Department of Biomedical Sciences, Section Physiology, University of Padova , Padova , Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rubini
authors.forename: Emanuele Luigi
authors.initials: EL
authors.lastname: Carniel
mesh_terms: D000818:Animals; D005260:Female; D008170:Lung Compliance; D008176:Lung Volume Measurements; D008297:Male; D008954:Models, Biological; D011175:Positive-Pressure Respiration; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012063:Relaxation; D012143:Respiratory Physiological Phenomena; D013312:Stress, Physiological; D013990:Tidal Volume