Respiratory failure is generally not graded; instead, it is classified into types. There are two types, Type I and Type II. Type I is characterized by an oxygen tension lower than 60 mmHg, at which point, there is no increase in carbon dioxide, and the carbon dioxide level is normal. Type II respiratory failure is when the oxygen tension is below 60 mmHg, accompanied by an increase in carbon dioxide, which is then termed Type II respiratory failure. Regarding respiratory failure, it is classified by type and not by severity grade. This means that once it meets these criteria, it is referred to as respiratory failure, and at this point, some emergency treatments to improve low oxygen levels are necessary. Therefore, respiratory failure is generally not graded into mild, moderate, or severe degrees. It is only differentiated into different types. Of course, there are different severity levels in respiratory failure, but we generally do not apply a specific degree of severity.