Study design: Literature review. Objectives: The recognized effect of breathing on venous return and cardiac output has not been assessed in the spinal cord injury (SCI) patient. To test this effect indirectly, the breathing capacity and blood pressure have been compared at various levels of SCI. Setting: SCI service, Massachusetts, USA. Methods: Spinal cord-injured subjects with complete motor paralysis were studied. The forced vital capacity (FVC) (one study, 455 subjects, 91% male) was compared with the mean blood pressure (MBP) (one study, 461 subjects, 100% male) of subjects by level of paralysis.