Other noninvasive devices were developed during the polio epidemics to assist ventilation and to facilitate weaning from the iron lung. Two of these, the rocking bed and the intermittent abdominal pressure ventilator, work on the principle of movement of the abdominal contents and diaphragm to facilitate breathing.

 

The intermittent abdominal pressure ventilator has a motorized inflatable bladder that fits over the abdomen. The motor inflates the bladder, which pushes the diaphragm upward to facilitate exhalation.When the bladder deflates, the diaphragm returns to its resting position, allowing for passive inhalation.

 

The rocking bed is a motorized bed that moves continously in a longitudinal plane from the Tredelenburg position to the reverse Tredelenburg position. In the reverse Tredelenburg position, the diaphragm and abdominal contents are pulled downward, which assists inhalation. When the bed rocks to the Trendelenburg position, the abdominal contents and diaphragm are pushed upward, which assists expiration.