The double sigmoidal nature of the mouse pressure-volume (PV) curve is well recognized but largely ignored. This study systematically examined the effect of inflating the mouse lung to 40 cm H2O transrespiratory pressure (Prs) in vivo. Adult BALB/c mice were anesthetized, tracheostomized, and mechanically ventilated. Thoracic gas volume was calculated using plethysmography and electrical stimulation of the intercostal muscles. Lung mechanics were tracked during inflation-deflation maneuvers using a modification of the forced oscillation technique. Inflation beyond 20 cm H2O caused a shift in subsequent PV curves with an increase in slope of the inflation limb and an increase in lung volume at 20 cm H2O. There was an overall decrease in tissue elastance and a fundamental change in its volume dependence. This apparent "softening" of the lung could be recovered by partial degassing of the lung or applying a negative transrespiratory pressure such that lung volume decreased below functional residual capacity. Allowing the lung to spontaneously recover revealed that the lung required approximately 1 h of mechanical ventilation to return to the original state. We propose a number of possible mechanisms for these observations and suggest that they are most likely explained by the unfolding of alveolar septa and the subsequent redistribution of the fluid lining the alveoli at high transrespiratory pressure.

Item Type:	Refereed Article
Research Division:	Biomedical and Clinical Sciences
Research Group:	Cardiovascular medicine and haematology
Research Field:	Respiratory diseases
Objective Division:	Health
Objective Group:	Clinical health
Objective Field:	Clinical health not elsewhere classified
UTAS Author:	Zosky, GR (Professor Graeme Zosky)
ID Code:	89479
Year Published:	2008
Web of Science® Times Cited:	39
Deposited By:	Medicine
Deposited On:	2014-03-05
Last Modified:	2014-03-05
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