Extreme air pressure variations or unusually light or heavy air pressure can cause barotraumatic injuries to pressure-sensitive organs, such as the ear and sinuses. Organs may be indirectly injured if too fast an atmospheric pressure change induces nitrogen to form gas bubbles in the blood. This happens to divers who surface too quickly after scuba diving while breathing compressed oxygen, and is called Caisson disease or the bends. Symptoms include pain in the joints and paralysis. It can be fatal.
Any change in the air pressure is likely to affect the density of oxygen in the air. If the air becomes thin, then the lungs cannot extract oxygen as efficiently as usual, causing high-altitude anoxia.