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 pneu mothorax induction (intrathoracic injection of 8 ml of room air; 50% collap se). Pneumothorax increased respiratory system and lung elastances and visc oelastic/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 significan tly after pneumothorax induction independently of temporal evolution. In bo th groups lung collapse, hyperinflation, and interstitial and alveolar edem a were present. Additionally, in PTX.60 group the central airways calibre d iminished in relation to PTX.30. In conclusion pneumothorax yields changes in respiratory system and lung elastic and viscoelastic parameters, which a re related to alveolar collapse and edema, respectively. Temporal evolution of pneumothorax also leads to changes in lung resistive pressure, probably because of airway narrowing. (C) 2000 Published by Elsevier Science B.V. A ll rights reserved.