The signs and symptoms of respiratory failure depend on its underlying cause and the levels of oxygen and carbon dioxide in the blood.
A low oxygen level in the blood can cause shortness of breath and air hunger (feeling like you can't breathe in enough air). If the level of oxygen is very low, it also can cause a bluish color on the skin, lips, and fingernails. A high carbon dioxide level can cause rapid breathing and confusion.
Some people who have respiratory failure may become very sleepy or lose consciousness. They also may develop arrhythmias (ah-RITH-me-ahs), or irregular heartbeats. These symptoms can occur if the brain and heart are not getting enough oxygen.