Hypocapnia

A state of decreased partial pressure of carbon dioxide in arterial blood (PaCO₂ <4.6 kPa or <35 mmHg), most often caused by alveolar hyperventilation and commonly associated with respiratory alkalosis.

Causes

• Psychological causes

  • Anxiety

  • Stress

  • Panic attacks

• Pulmonary causes

  • Asthma

  • Pneumonia

  • Pulmonary embolism

• Metabolic acidosis

  • Diabetic ketoacidosis (DKA)

  • Lactic acidosis

  • Renal failure-associated acidosis

• Physiological causes

  • Pain

  • Fever

  • Sepsis causing compensatory hyperventilation

  • High altitude exposure

  • Pregnancy

  • Strenuous exercise

• Mechanical overventilation during critical care