To the Editor.—As the senior author of the article on filtration characteristics of the Bentley micropore blood filter (Arch Surg 112:222-225, 1977), I was most interested to read of the complication of embolization of air retained in the filter cited by Dr Wuller (Arch Surg 112:1020, 1977). We have primed all of our micropore filters by inverting them in-line so as to fill the filter against the flow of gravity. This has allowed air to be expelled from the filters. While this should obviate the complication referred to by Dr Wuller, it nevertheless remains a possibility and represents a complication we have not previously recognized.
I do not believe, however, that it is either desirable or necessary to set up controlled double-blind human experiments to demonstrate that formed debris administered during blood transfusions is harmful. This has already been scientifically demonstrated in animals (Ann Surg, 185:92-99, 1977). To perform