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Multiple pressure–volume loops recorded with sinusoidal low flow in a porcine acute respiratory distress syndrome model
Author(s) -
Bitzén Ulrika,
Enoksson Jens,
Uttman Leif,
Niklason Lisbet,
Johansson Leif,
Jonson Björn
Publication year - 2006
Publication title -
clinical physiology and functional imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.608
H-Index - 67
eISSN - 1475-097X
pISSN - 1475-0961
DOI - 10.1111/j.1475-097x.2006.00660.x
Subject(s) - ards , medicine , tidal volume , expiration , ventilation (architecture) , mechanical ventilation , pulmonary gas pressures , lung volumes , positive end expiratory pressure , anesthesia , elastance , transpulmonary pressure , respiratory system , acute respiratory distress , respiratory physiology , respiratory distress , lung , physics , thermodynamics
Summary Objectives: To develop a method for automatic recording of multiple dynamic elastic pressure–volume ( P el / V ) loops. To analyse the relationship between multiple dynamic P el / V loops and static P el / V loops in a porcine model of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). To test the hypothesis that increasing lung collapse and re‐expansion with decreasing positive end expiratory pressure (PEEP) can be characterized by hysteresis of the P el / V loops. Material and Interventions: In eight anaesthetized and paralysed pigs, ALI/ARDS was induced by inhalation of dioctyl sodium sulfosuccinate and large tidal volume ventilation. Measurements and Results: The physiological and histopathological findings indicated a status mimicking an early stage of ALI/ARDS. Automatically, a series of dynamic P el / V loops from different PEEP levels were recorded with the sinusoidal flow modulation method using a computer‐controlled ventilator. During expiration, resistance increased more than twofold. For each step of lower starting pressure, the inspiratory limb was displaced towards lower volume indicating derecruitment. Recruitment occurred between 20 and 40 cm H 2 O. The expiratory curves, all starting from 50 cm H 2 O, overlapped. Hysteresis increased significantly in loops recorded from lower PEEP levels. Viscoelasticity explained differences between static and dynamic P el / V loops. Conclusions: Automated multiple P el / V loop determination is feasible and provides comprehensive information on lung derecruitment and recruitment. It requires determination of volume dependence of expiratory resistance. An expiratory curve serves as a reference to inspiratory curves and provides information about hysteresis.