title: The Effects of Prone with Respect to Supine Position on Stress Relaxation, Respiratory Mechanics, and the Work of Breathing Measured by the End-Inflation Occlusion Method in the Rat.
abstract: OBJECTIVE
  The working hypothesis is that the prone position with respect to supine may change the geometric configuration of the lungs inside the chest wall, thus their reciprocal mechanical interactions, leading to possible effects on stress relaxation phenomena and respiratory mechanics.
  
  
  METHODS
  The effects of changing body posture from supine to prone on respiratory system mechanics, particularly on stress relaxation, were investigated in the rat by the end-inflation occlusion method.
  
  
  RESULTS
  In the prone with respect to supine position, an increment of the frictional resistance of the airway (from 0.13 ± 0.01 to 0.19 ± 0.02 cm H2O/l sec(-1), p < 0.05) and a decrement of the stress relaxation-linked pressure dissipation (from 0.51 ± 0.05 to 0.45 ± 0.05 cm H2O/l sec(-1), p < 0.01) were found. Respiratory system elastance and total resistive pressure dissipation did not change significantly. Accordingly, a significant increase of the frictional "ohmic" mechanical inspiratory work of breathing and a decrease of the visco-elastic work of inspiration were demonstrated, while no significant changes occurred for the total mechanical work of breathing and its total resistive and elastic components.
  
  
  CONCLUSIONS
  It is concluded that postural changes affect the visco-elastic characteristics of the respiratory system and the related stress relaxation phenomena by influencing the disposition and relation of the lungs inside the chest wall and their relative geometrical configuration, and the interaction phenomena of the constitutive parenchymal structures, i.e., elastin and collagen fibers. Since the prone position resulted in no serious or disadvantageous respiratory system mechanical derangement, it is suggested it may be usefully applied in nursing or for therapeutic goals.
authors.affiliation: Physiology Section, Department of Biomedical Sciences, University of Padova, Via Marzolo 3, 35100, Padua, Italy. alessandro.rubini@unipd.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rubini
mesh_terms: D000403:Airway Resistance; D000818:Animals; D004548:Elasticity / Q000502:physiology; D005260:Female; D017276:Friction / Q000502:physiology; D008297:Male; D016684:Prone Position / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012063:Relaxation / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D013312:Stress, Physiological; D016683:Supine Position / Q000502:physiology*; D014939:Work of Breathing / Q000502:physiology*
keywords: Body posture; Rat; Respiratory mechanics; Stress relaxation; Work of breathing