Simultaneously, however, PaO 2 and PaCO 2 should be measured, so that subsequent O 2 therapy can be applied rationally. This, however, gives no margin of safety. On the other hand, if PaO 2 is increased further, increases in arterial and venous saturation are much smaller and the risks of oxygen therapy increase. 60 mmHg breathing room air will seldom benefit from O 2 therapy. O 2 toxicity and CO 2 narcosis.
Oxygen toxicity has three chief manifestations.
Second, at lower levels and longer exposures O 2 causes pulmonary disease with capillary damage, leak, and ultimately fibrosis or scarring, which can be fatal. At sea level, breathing pure O 2 can cause symptoms of pulmonary O 2 toxicity within 24 hours. 150 mmHg can cause damage to retinal capillaries with subsequent fibrosis and blindness, called retrolental fibroplasia. Carbon dioxide narcosis occurs when hypoxemic patients are given O 2 to breathe and PaCO 2 increases sharply and progressively with severe respiratory acidosis, somnolence and eventually coma. Therefore PaO 2 rose and the patient stopped breathing.