Recurrent hyperventilation tetany due to mild asthma

Abstract

There is uncertainty about the boundaries, definition and diagnosis of disorders related to hyperventilation (1,2). The original definition of the hyperventilation syndrome implied an association between anxiety and hyperventilation (3), but more recent reports suggest that severe symptomatic hyperventilation can occur in the absence of reported anxiety and psychiatric morbidity (4-6). The interrelationship of anxiety, panic and hyperventilation is complex and controversial (7). Hyperventilation implies excessive respiratory drive and hypocapnia. Many organic disorders are associated with hypocapnia (2) which can occur in the early stages of most respiratory diseases, left ventricular failure, pulmonary embolus, chronic pain, most major system failures, and drug overdoses (e.g. aspirin). Hypocapnia also occurs with physiological states such as prolonged talking, pyrexia, pregnancy and in the second half of the menstrual cycle. Hyperventilation can cause the sudden onset of alarming symptoms due to both increased chest wall movement, and vasoconstriction and nervous hyperirritability induced by hypocapnic alkalosis. Hypocapnia is only of clinical relevance if it is associated with symptoms, and it has been suggested that hyperventilation only becomes self perpetuating and ultimately chronic if the patient misattributes these symptoms to serious disease, especially if the physician fails to recognise the true nature of the complaints (8). Such misattribution may prove to be the key to the etiology of the hyperventilation syndrome. Mild and moderate asthma can cause profound hypocapnia (9) and clinical experience suggests that asthma is often one of a number of factors contributing to the etiology of recurrent symptomatic hyperventilation (10). However, there is no evidence that an asthmatic, in the absence of other factors, can present with symptoms of hypocapnia sufficiently severe to overshadow the symptoms of airflow obstruction and