| Central nervous system | Pain Hyperventilation syndrome Anxiety and panic disorders Psychosis Fever Intracranial pathology (eg, stroke, meningitis encephalitis, tumors, traumatic injury) Drug withdrawal |
| Drugs and toxins | Overdoses of salicylate, methylxanthine, catecholamines, nicotine Progesterone and medroxyprogesterone Doxapram Toxic shock |
| Pulmonary | Hypoxemia Pneumothorax Pneumonia Pulmonary edema Pulmonary embolism Aspiration Interstitial lung disease |
| Miscellaneous | High altitude Right-to-left shunts Pregnancy Hyperthyroidism Severe anemia Hyperventilation on mechanical ventilation Recovery phase metabolic acidosis Chronic liver disease Prolonged paralysis |
