Effect of Heimlich valve and underwater seal on lung expansion after pulmonary resection

Background: A study was undertaken to compare the physiologic and clinical effects of Under Water Seal (UWS) versus Heimlich Valve (HV) pleural drainage systems in the treatment of patients following pulmonary resection. Methods: Twenty patients post pulmonary resection (lobectomy - 13, wedge resections - 6, bullectomy - 1) were studied. The relative intrapleural pressures were measured by a flow meter that was subsequently connected to a UWS and to an HV through straight and curved chest tubes. The quantity of the air leak, if present, was also gauged by a flow meter, and the degree of lung expansion was recorded by chest radiography. Results: At resting tidal volume the relative intrapleural pressures measured when using an HV were more negative than those measured when using a UWS. The differences between end-inspiratory and endexpiratory relative intrapleural pressures were greater with a UWS than with an HV. The forced endexpiratory pressures were higher with an HV than a UWS. Conclusions: The HV maintains more negative intrapleural pressure than a UWS, promotes more effective removal of excess air from the pleural space and ensures more complete expansion of the lung. The HV is superior to a UWS in physiologic postoperative conditions, and may also be preferable in the management of patients with an air leak and residual spaces.