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.