V. V. Dobaria1, R. Cameron1, E. Aguayo1, K. Bailey1, Y. Seo1, Y. Sanaiha1, P. Benharash1 1University Of California – Los Angeles,Cardiac Surgery,Los Angeles, CA, USA
Introduction:
Chest drainage systems are routinely used to achieve proper drainage of the pleural space after cardiac and thoracic operations. The ideal chest drainage system would evacuate air and fluid, creating a negative intrapleural pressure that would facilitate lung expansion and induction of adhesions to prevent accumulation of matter in this potential space. While the appropriate level of suction that would create the most rapid resolution of air leaks and pleural collections has been debated, data on the actual intrapleural pressure during the use of chest drainage systems is lacking. Columns of fluid collecting in the drainage tube may alter the transmission of optimal pressure to the patient. The present study was performed to evaluate differences along the length of the chest drain circuit using an ex-vivo model.
Methods:
An ex-vivo apparatus coupled to a commercial pleural drainage system was devised to provide calibrated manometer measurements and user-defined levels of suction and air leak. Simultaneous pressure measurements were obtained at the outlet of the drainage system and at the simulated entry site into the patient where air could be introduced. Systematic trials were conducted with increasing levels of water between the patient and drainage modules and at various levels of suction and air leak rates. Signals were recorded at 100Hz on a PC and analyzed using two-way t-tests. Significance was taken at P-value < 0.05.
Results:
With no obstruction, the pleural drainage system provided precise levels of negative pressure at the patient level (10-40 cm H2O). Addition of fluid in the drainage tubing as a water trap caused significant differences in levels of transmitted suction as shown in Figure. With increasing air leakage and fluid volume, the pressure differential between the drainage system and patient increased significantly (1.14 ± 0.04 to 36.69 ± 0.15cm H2O, P<0.001). While off suction increasing levels of obstruction from 0 to 22 cm of water, led to a development of positive intrapleural pressures varying from 2.6 ± 0.4 to 12.1 cm H2O, P< 0.001).
Conclusion:
The findings of the study suggest that while commercially available pleural drainage systems provide predictable levels of suction at the level of the device, intrapleural pressures can be highly variable and depend on complete patency of connecting tubes. In fact, high levels of positive pressure may develop and precipitate lung collapse and therefore prolong the duration of air leaks. This finding may explain the highly variable rates of reported postoperative air leak. Systems able to modulate the level of suction based on actual intrapleural pressures may enhance recovery after procedures requiring tube thoracotomy.
