Sampling of lung interstitial fluid in intact dog

Abstract

This paper reports a method of sampling fluid from the peribronchial—perivascular space (PBVS) of the lungs in intact closed chest dogs. The PBVS was sampled by introducing a wick catheter into the PBVS through a mediastinoscope. The right lymph duct was cannulated by the method of Vriem and Ohkuda [J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 54:199, 1983] for collection of lymph to compare to peribronchial fluid. The colloid osmotic pressure (COP) of PVBS and right lymph duct fluid (RLDF) were compared in a series of dogs infused with lactated Ringer's solution (LR) and lactated Ringer's combined with three other conditions: left atrial balloon inflation (LRB), oleic acid infusion (LRO), and oleic acid infusion and left atrial balloon inflation (LROB). Prior to LR infusion, the volume of samples of fluid from the PBVS wicks was inadequate for measuring COP (<4 μl). This difference was significant only in the later samples at 3, 4, and 5 hr in the LR and LRB groups. In the LRO and LROB groups, protein content and amount of fluid sampled were greater than in the LR and LRB groups, but the mean COPs of the wick PBVS and RLDF were not significantly different. This method of directly sampling interstitial fluid from the lungs of dogs without thoracotomy confirms the high COP of fluid from the lung interstitium. This method of PBVS fluid sampling is potentially feasible in a human patient undergoing mediastinoscopy.