In spontaneous or accidental pneumothorax with increased tension, it is frequently necessary to relieve the intrapleural pressure. In certain cases, aspiration suffices. In other cases, the air reaccumulates so rapidly that it is necessary to provide for its continuous escape. This is best accomplished by inserting an intercostal tube and using one-way valve drainage.
The cannula here illustrated was devised to replace the usual drainage tube. It is a silver tube 4 mm. in diameter and 4 cm. in length, with a flange near the outer end and perforations near the inner end. The flange has two slits, one on each side of the tube. The cannula is fitted with a steel trocar.
The length of the cannula projecting through the chest wall may be varied by placing different thicknesses of sterile gauze beneath the flange before it is inserted. Continuous escape of air is insured by perforations in the