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Changes in the lung after prolonged positive pressure ventilation in normal baboons
S G Simonson1, Y C Huang, P J Fracica
1Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Journal of Critical Care
|June 1, 1997
Summary
Prolonged mechanical ventilation in baboons worsened gas exchange and decreased lung compliance. Minor lung ultrastructural changes and mild inflammation were observed.
Area of Science:
- Pulmonary Medicine
- Critical Care Medicine
- Respiratory Physiology
Background:
- Positive pressure ventilation is a cornerstone of respiratory support in critically ill patients.
- However, the long-term effects of mechanical ventilation on lung ultrastructure and function in primates remain incompletely understood.
Purpose of the Study:
- To investigate the cardiopulmonary and morphological consequences of 4-day mechanical ventilation in healthy baboons.
- To assess the impact of positive pressure ventilation on lung ultrastructure and gas exchange.
Main Methods:
- Six baboons were mechanically ventilated for 96 hours with PEEP of 2.5 cm H2O and tidal volume of 12-15 mL/kg.
- Physiological parameters, ventilation-perfusion (VA/Q) distribution, and lung morphometry were assessed serially and at the study's conclusion.
Main Results:
- Mechanical ventilation led to decreased arterial Po2, increased shunt fraction, and worsened VA/Q mismatch.
- Respiratory system compliance decreased by 30%, with no significant changes in lung edema or surfactant composition.
- Morphological analysis revealed increased polymorphonuclear cells, type II cell volume, vacuolated endothelial cells, and bare basement membranes.
Conclusions:
- Four days of positive pressure ventilation impairs gas exchange and reduces lung compliance in healthy baboons.
- These functional changes are associated with minimal ultrastructural alterations and mild inflammatory responses in the lung.