Oxygen therapy has the best effect on hypotonic hypoxia. The partial pressure of blood oxygen in hypotonic hypoxic patients is continuously reduced, at this time, oxygen therapy can be used to inhale different concentrations of oxygen, so that the concentration of inhaled oxygen and the partial pressure of oxygen in alveolar gas can gradually increase, which can raise the partial pressure of arterial blood oxygen and achieve the purpose of alleviating or correcting hypoxemia. Oxygen therapy is one of the methods to treat hypoxemia. Within certain limits, oxygen therapy can prevent or treat hypoxemia, but it cannot reverse the primary lung disease. Due to the increased respiratory and cardiac work caused by hypoxemia, the correction of hypoxemia after oxygen therapy reduces the stimulation of respiratory center and heart, which can reduce respiratory or cardiac work and oxygen consumption. Therefore, oxygen therapy is more effective for hypoxia, especially hypotonic hypoxia.