Fig. 2. Off-site coagulation downstream from the collagen and tissue factor patch (a) fibrin formation (magenta) was observed spreading along the channel in some devices, including at the outlet. The image shown is a representative image of a pressure relief device, and depicts the outlet situated downstream from the collagen and tissue factor patch. The image was taken 30 minutes after initiation of the experiment using a 4× objective. (b) Clots were observed emerging from the end of the waste tubing. Collecting into a vessel of concentrated sodium citrate was not sufficient to prevent this.