Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

Abstract: We have previously reported that lymph from the chronic sheep lung lymph preparation contains 25-60% lymph from nonpulmonary sources. In subsequent studies we found that the lymph flow rate from cannulated lymph vessels depends on the resistance and position of the lymph cannula. Because we did not account for these factors in our estimate of the amount of nonpulmonary lymph in the sheep lung lymph preparation, our data were not accurate. We probably overestimated the amount of nonpulmonary lymph. However, the presence of nonpulmonary lymph remains a potentially serious problem with the sheep lung lymph preparation.
Overestimation of sheep lung lymph contamination.