b. Exhalation Phase. When the rescuer removes his mouth from the casualty
(breaks the seal over the casualty's airway), the higher air pressure in the casualty's
respiratory system causes air to rush from the airway and into the atmosphere. The rib
cage and the diaphragm resume their normal positions (the chest falls and the
diaphragm pushes into the chest cavity by resuming its dome-like shape). These
actions result in air being forced out of the lungs, just as in normal exhalation.
EFFECTS OF CHEST COMPRESSIONS
a. The heart is located between the sternum and the spine. If the sternum is
pressed down (depressed) far enough into the chest cavity (1 1/2 to 2 inches in an
adult), the heart is compressed between the sternum and the spine (figure 2-1A). Blood
is then forced out of the ventricles and into the arteries.
Figure 2-1. Effects of chest compression. A Compression. B Release.