Temporal evolution of pneumothorax: respiratory mechanical and histopathological study

Respiratory mechanics, chest wall configuration, and lung morphometry were determined in rats before and at 30 (PTX.30) and 60 (PTX.60) min after pneumothorax induction (intrathoracic injection of 8 ml of room air; 50% collapse). Pneumothorax increased respiratory system and lung elastances and viscoelastic/inhomogeneous pressures in both groups, but respiratory system and lung resistive pressures increased only in PTX.60 group. Antero-posterior diameters at the third intercostal space and xiphoid levels, circumference at xiphoid level, and thoracic cephalo-caudal diameter increased significantly after pneumothorax induction independently of temporal evolution. In both groups lung collapse, hyperinflation, and interstitial and alveolar edema were present. Additionally, in PTX.60 group the central airways calibre diminished in relation to PTX.30. In conclusion pneumothorax yields changes in respiratory system and lung elastic and viscoelastic parameters, which are related to alveolar collapse and edema, respectively. Temporal evolution of pneumothorax also leads to changes in lung resistive pressure, probably because of airway narrowing.