Final answer:
Sustained positive acceleration (+Gz) force leads to decreased blood flow to the brain, similar to orthostatic hypotension, due to blood pooling in the lower body and reduced cerebral blood pressure.
Step-by-step explanation:
One of the circulatory effects caused by a sustained positive acceleration (+Gz) force is decreased blood flow to the brain. During positive Gz acceleration, the force acts from the head toward the feet, which can cause blood to move away from the brain and pool in the lower parts of the body. This can lead to decreased blood pressure in the cerebral vessels and consequently, reduced blood flow to the brain. If this situation is sustained and the body can't compensate by increasing cardiac output or constricting blood vessels, it might result in a condition similar to orthostatic hypotension, where blood pressure drops as one stands up, potentially causing dizziness or fainting.