DDx

Acute

• Asthma, pneumonia, pulmonary edema, pneumothorax, pulmonary embolus, metabolic acidosis, acute respiratory distress syndrome, panic attack

• Airflow obstruction (asthma, chronic obstructive pulmonary disease, upper airway obstruction), restrictive lung disease (interstitial lung disease, pleural thickening or effusion, respiratory muscle weakness, obesity), pneumonia, pneumothorax, pulmonary embolism, aspiration, acute respiratory distress syndrome

• Myocardial ischemia, congestive heart failure, valvular obstruction, arrhythmia, cardiac tamponade

• Acidosis, hypercapnia, sepsis

• Anemia, methemoglobinemia

• Anxiety