To the Editor.—The article by Kurtz and Hsu in the Archives (115:73-74, 1980) regarding resolution of chylothorax after positive end-expiratory pressure (PEEP) ventilation is enlightening and a logical approach to the clinical problem. Several years ago, Bittar and I1 undertook to determine the mechanism by which patients receiving PEEP ventilation acquired a positive water balance.2 We envisioned PEEP as retarding lymphatic return to the central venous pool, thereby allowing fluid to accumulate in the more peripheral interstitium.
To test this hypothesis, we anesthetized dogs and cannulated the thoracic duct above the diaphragm in a manner that allowed us to measure the volume of lymph flowing per unit of time. We measured lymph flow during mechanical ventilation before, during, and after PEEP and found that there was a highly significant relationship between application of PEEP and reduction of lymph flow. Furthermore, when PEEP was removed lymphatic flow