Acute respiratory failure refers to a situation in which the patient's original respiratory function is normal, but due to some sudden reasons, such as airway obstruction, drowning, drug poisoning, and central nervous and muscular diseases, breathing is suppressed, and the body often has no time to compensate. If it is not diagnosed in time and effective control measures are not taken as soon as possible, it can often be life-threatening. However, the original respiratory function of patients with this type of respiratory failure is usually good. If rescued in time and effectively, the prognosis is often better than that of chronic respiratory failure. However, it is also common to see patients with poor original respiratory function in clinical practice. Due to some sudden reasons, common respiratory infections can cause airway obstruction, which can cause a sharp increase in PaCO2 and a sharp decrease in PaO2. Clinically, this type of respiratory failure is usually classified as acute exacerbation of chronic respiratory failure.