Evaluation of extracorporeal perfusion catheters using a standardized measurement technique--the M-number

Cannulas used for extracorporeal circulating devices are made in many shapes and sizes. Side hole placement, length, and wall thickness can make the pressure-flow characteristics of catheters with similar French sizes quite different in their actual performance. A single value, the M-number, has been developed that describes the pressure-flow characteristics of an individual cannula. This number can be used to compare catheters and assess their potential utility for given bypass requirements. The M-numbers for commonly used catheters that are placed by extrathoracic dissections are determined. Clinical situations are presented that demonstrate applications of the M-number.