[Tetany, spasmophilia, hyperventilation syndrome: theoretical and therapeutic synthesis].

The hyperventilation syndrome (HVS), characterised by multiple somatic symptoms induced by inappropriate hyperventilation, constitutes the physiopathological manifestation of a common disorder in general medicine. As a synonym of spasmophilia or tetany, it has the advantage of offering diagnostic criteria, even though the latter are still vaguely defined. But its definition allows for objective measurements: indeed, a decrease in PCO2 during a hyperventilation provoking test and an abnormally low PCO2 rate at rest can be easily quantified. Moreover, the HVS concept offers a treatment which is both structured (respiratory reeducation, psychotherapy and pharmacology) and efficient. Yet, a number of scientific uncertainties still exist. There is no general agreement regarding the criteria which should be taken into account in a hyperventilation provoking test in order to diagnose an hyperventilation syndrome; the specificity of such a test is weak and a placebo can induce as many symptoms as can a HVS. Respiratory reeducation has good results but does not necessarily have an effect on PCO2. Some therapists see in it no more than a mechanism of relaxation and a rational explanation of frightening symptoms. This has led some authors to reject the term "hyperventilation syndrome" and to prefer the expression "chronic hyperventilation of unknown origin".