An occlusion catheter system for occlusion or partial occlusion of a relatively large vessel having an internal surface, the occlusion catheter system comprising: an inflation catheter member having a stiffener member including a lumen therein, a first inflation lumen, a proximal catheter end, and a distal catheter end, the inflation catheter member defining a longitudinal axis, the inflation catheter member having an atraumatic tip on the distal catheter end; an occlusion balloon having an internal balloon space, an external balloon surface, a proximal balloon end and a distal balloon end, the proximal and distal balloon ends (1840c,1840d) connected to the inflation catheter member between the proximal catheter end and the distal catheter end, the occlusion balloon centered along the longitudinal axis in an inflated configuration, the first inflation lumen being in fluid communication with the internal balloon space; a proximal sensor mounted to the catheter member proximally relative to the occlusion balloon; said occlusion catheter system being characterized in that it further comprises: a distal side port comprising a port configured to sense a parameter or comprising a distal sensor, the distal side port being attached to the inflation catheter member and being positioned distally of the occlusion balloon and being in fluid communication with the lumen in the stiffener member a controller in communication with the proximal sensor and the distal side port; and a pump in fluid communication with the occlusion balloon, the controller configured to one of introducing pressurized fluid into the occlusion balloon and withdrawing fluid from the occlusion balloon based on measurements from the proximal sensor and the distal side port. an inflation catheter member having a stiffener member including a lumen therein, a first inflation lumen, a proximal catheter end, and a distal catheter end, the inflation catheter member defining a longitudinal axis, the inflation catheter member having an atraumatic tip on the distal catheter end; an occlusion balloon having an internal balloon space, an external balloon surface, a proximal balloon end and a distal balloon end, the proximal and distal balloon ends (1840c,1840d) connected to the inflation catheter member between the proximal catheter end and the distal catheter end, the occlusion balloon centered along the longitudinal axis in an inflated configuration, the first inflation lumen being in fluid communication with the internal balloon space; a proximal sensor mounted to the catheter member proximally relative to the occlusion balloon; said occlusion catheter system being characterized in that it further comprises: a distal side port comprising a port configured to sense a parameter or comprising a distal sensor, the distal side port being attached to the inflation catheter member and being positioned distally of the occlusion balloon and being in fluid communication with the lumen in the stiffener member a controller in communication with the proximal sensor and the distal side port; and a pump in fluid communication with the occlusion balloon, the controller configured to one of introducing pressurized fluid into the occlusion balloon and withdrawing fluid from the occlusion balloon based on measurements from the proximal sensor and the distal side port. a distal side port comprising a port configured to sense a parameter or comprising a distal sensor, the distal side port being attached to the inflation catheter member and being positioned distally of the occlusion balloon and being in fluid communication with the lumen in the stiffener member a controller in communication with the proximal sensor and the distal side port; and a pump in fluid communication with the occlusion balloon, the controller configured to one of introducing pressurized fluid into the occlusion balloon and withdrawing fluid from the occlusion balloon based on measurements from the proximal sensor and the distal side port.