The present invention is directed to a modular pressure infuser apparatus adapted to allow a user to modify the configuration of the pressure infuser apparatus by utilizing one or more interchangeable manual and/or automatic pumps to inflate a pressure infuser bag of the pressure infuser apparatus. The modular configuration of the pressure infuser apparatus permits the user to detach and reattach a motorized pump and/or a manual pump to the pressure infuser bag quickly, easily, and efficiently without decreasing the air pressure of the pressure infuser bag. By providing selectively removable pump modules, the user can select the configuration of the pressure infuser apparatus that is best adapted to the needs of the patient. A pressure release valve is configured to regulate the pressure of the pressure infuser bag.