Hyperventilation syndrome

What it is

Hyperventilation syndrome is listed among the neuropsychiatric diseases that sit on the differential diagnosis of anaphylaxis, beside fright and panic disorder, somatoform disorder such as psychogenic dyspnea and vocal cord dysfunction, and dissociative disorder and conversion such as globus hystericus.

The word also names a maneuver. In typical absence seizures the investigation of choice is the EEG and the maneuver that helps make the diagnosis is hyperventilation; the classical finding is 3 Hz spike and wave discharges per second. Absence is the type of epilepsy precipitated by hyperventilation.

How it presents

The case written out is a 29-year-old woman who comes to the ED for hyperventilation. Her respiratory rate is 28 breaths per minute with an oxygen saturation of 100% on room air. She is able to speak in full sentences, and she says that she cannot breathe and that her hands and feet are cramping up. She denies any trauma, past medical history or illicit drug use. Chest auscultation reveals clear breath sounds bilaterally and the chest radiograph is normal. On reevaluation she reports that she is breathing better, with a respiratory rate of 12 and a saturation of 100% on room air.

Those extremity symptoms are typical of carpal-pedal spasm seen with tetany, which is a result of a transient decrease in calcium serum levels secondary to a respiratory alkalosis. Put the other way round, the alkalemic environment decreases ionized calcium levels, and what follows is paresthesias, carpal spasm and tetany. So the cramping hands are not a second complaint beside the breathing: they are what the respiratory alkalosis does to the ionized calcium.

As a physical finding, hyperventilation on examination points to acidosis, sepsis, salicylate poisoning or anxiety. The other findings separate from it: absent or diminished breath sounds mean decreased air movement, in COPD, severe asthma, pneumothorax, tension pneumothorax or hemothorax; accessory muscle use means muscle weakness and fatigue, in respiratory failure, severe COPD or severe asthma; expiratory or mixed stridor means air flow obstruction below the vocal cords, in croup, foreign body or bacterial tracheitis; and inspiratory stridor means air flow obstruction above the vocal cords, in foreign body, epiglottitis or angioedema.

Where the picture is a panic attack, the attack is a discrete period of intense fear or discomfort in which four or more of the following symptoms develop acutely and peak within 10 minutes: accelerated HR, palpitations, pounding heart, diaphoresis, trembling or shaking, sensation of shortness of breath or a choking feeling, chest pain, nausea, dizziness, lightheadedness, paresthesias, fear of dying, chills, or hot flushes. Such a person will often present to multiple EDs and be discharged after a workup is normal.