The normal value of partial pressure of carbon dioxide is 35-45 mmHg. The partial pressure of carbon dioxide is a relatively important indicator of respiratory acid-base balance disorders and can be used in clinical practice to assess whether a patient has respiratory failure problems. If the partial pressure of carbon dioxide is reduced, it indicates hyperventilation, mainly alveolar hyperventilation, with more exhaled carbon dioxide, which is seen in asthma, pneumonia and pulmonary infarction. Elevated partial pressure of carbon dioxide is seen in pulmonary edema, pulmonary heart disease, emphysema, severe asthma attacks, and can also be caused by large pulmonary atelectasis, thoracic disease, and pleural disease.