A surgical fastening instrument is provided. The pump may further include electrolysis electrodes within the first chamber for causing generation of a gas therein and to thereby expand the expandable diaphragm so that fluid is forced from the second chamber into a cannula. When tandem compressor assemblies are used, the pair of upwardly extending flanges provide clearance for a pair of rails which interconnect the tandem compressors without having to modify the foot plates.