Symptom reporting during voluntary hyperventilation and mental load: implications for diagnosing hyperventilation syndrome.

Hyperventilation is considered an important factor in the production of a variety of somatic symptoms. This complex of symptoms is called the Hyperventilation Syndrome (HVS). Recognition of symptoms during the hyperventilation provocation test (HVPT) is a widely used criterion for diagnosing HVS. The validity of this criterion is tested in the present study. Twenty-three patients suspected of HVS performed a HVPT (hyperventilation during 3 min) and a mental load task (Stroop Color Word Test; CWT). It appeared that about the same number of patients (61%) recognized symptoms during the HVPT as during the CWT (52%), despite severe hypocapnia in the first test and normocapnia in the second. Reporting of symptoms was significantly related to psychological state and trait measures (SCL-90 and STAI scores) and unrelated to the degree of hypocapnia. These data have far reaching consequences, as they not only undermine the validity of the HVPT, but also question the tenability of the concept of HVS.