Hyperventilation is breathing which occurs more deeply and/or more rapidly than normal.
Pathophysiology: CO 2 is ‘blown off ’, so that pCO 2 decreases.. Hyperventilation may be primary (‘psychogenic’) or secondary. A classical secondary cause is DKA — Kussmaul’s respiration represents respiratory compensation for a metabolic acidosis.
Secondary causes of hyperventilation
• Metabolic acidosis (eg DKA, uraemia, sepsis, hepatic failure).
• Poisoning (eg aspirin, methanol, CO, cyanide, ethylene glycol).
• Respiratory disorders (eg PE, asthma, pneumothorax).
Primary (psychogenic or inappropriate) hyperventilation
Typically, the patient is agitated and distressed with a past history of panic attacks or episodes of hyperventilation. They may complain of dizziness, circumoral paraesthesia, carpopedal spasm, and occasionally sharp or stabbing chest pain. Initial examination reveals tachypnoea with equal
air entry over both lung fields, and no wheeze or evidence of airway obstruction.
Investigations: It is always important to consider secondary causes (such as PE or DKA). Therefore, perform the following investigations:
• SpO 2.
• ABG if SpO 2 decreased , or if symptoms do not completely settle in a few minutes.
If symptoms do not completely settle in a few minutes, obtain:
• U&E, blood glucose, FBC.
- Do not sedate a patient who is hyperventilating.
- Once serious diagnoses have been excluded, reassure the patient with primary hyperventilation. Often this is all that is required, but it may be helpful to try simple breathing exercises (breathe in through nose — count of 8, out through mouth — count of 8, hold for count of 4 and repeat).
- Discharge the patient with advice for follow-up.
- If these simple measures fail, reconsider the diagnosis and refer the patient to the medical team for subsequent observation and treatment.