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[Comparative study of different methods of pleural drainage in an experimental model of pneumothorax].

OBJECTIVE
To observe the usefulness of several procedures for draining pneumothorax in an animal model and to identify the best pleural drainage system with minimal impairment of respiratory function.


METHOD
Thirty-four New Zealand white rabbits weighting 1687 +/- 78 g and aged a mean 59 days were randomly placed in groups as follows. Unilateral pneumothorax was induced in the first problem group (P1) rabbits (n = 10) by thoracostomy, with pleural drainage. In the second problem group (P2) of rabbits (n = 10), bilateral pneumothorax was similarly induced by thoracostomy with pleural drainage. The control groups underwent unilateral (C1; n = 7) and bilateral (C2; n = 7) thoracostomy and drainage. Every 7 minutes the chest tube was connected successfully in each animal to an underwater seal with a dead-space volume of 35.58 ml (neonatal Bülau unit) or to a 3,940 ml system (chest drainage unit) and to pleural aspirations of -5 and -20 cmH2O. We analyzed mortality, fluctuations of the hydrostatic column of the underwater seal, heart rate (HR), respiratory rate (RR), PaCO2, SaO2, pH and arterial blood gas measures.


RESULTS
Intraoperative mortality was significantly higher (particularly in the P2 group) when connection was to a large volume system without aspiration. Recovery after pneumothorax was more satisfactory with aspiration of -5 and -20 cmH2O.


CONCLUSIONS
The results suggest that a pleural drainage unit with a large dead space between the pleural cavity and the underwater seal is a frequent cause of respiratory failure or insufficiency. We believe that when an underwater seal without pleural suction is applied, the Bülau unit should be used with the smallest possible volume.