DOUBLE-BLIND PLACEBO-CONTROLLED STUDY OF THE HYPERVENTILATION PROVOCATION TEST AND THE VALIDITY OF THE HYPERVENTILATION SYNDROME

Background Hyperventilation syndrome (HVS) describes a set of somatic and psychological symptoms thought to result from episodic or chronic hyperventilation. Recognition of symptoms during the hyperventilation provocation test (HVPT) is the most widely used criterion for diagnosi s of HVS. We have investigated the validity of the HVPT and of the con cept of HVS. Methods in a randomised, double blind, crossover design, the ability of 115 patients with suspected HVS to recognise symptoms d uring the HVPT was compared with the ability to recognise symptoms dur ing a placebo test (isocapnic overbreathing, with carbon dioxide level s maintained by manual titration). 30 patients who had positive result s on the HVPT underwent ambulatory transcutaneous monitoring of pCO(2) to ascertain whether they hyperventilated during spontaneous symptom attacks. Findings Of the 115 patients who underwent the HVPT and the p lacebo test, 85 (74%) reported symptom recognition during: the HVPT (p ositive diagnosis HVS). Of that subset, 56 were also positive on the p lacebo test (false-positive), and 29 were negative on the placebo test (true-positive). False-positive and true-positive patients did not di ffer in symptom profile or in physiological variables. During ambulato ry monitoring (15 true-positive, 15 false-positive) 22 attacks were re gistered. Transcutaneous end-tidal pCO(2) decreased during only seven. The decreases were slight and apparently followed the onset of the at tack, which suggests that hyperventilation is a consequence rather tha n a cause of the attack. There were no apparent differences between fa lse-positive and true-positive patients. Interpretation The HVPT is in valid as a diagnostic lest for HVS. Hyperventilation seems a negligibl e factor in the experience of spontaneous symptoms. The term HVS shoul d be avoided.