VOLUNTARY HYPERVENTILATION - THE INFLUENCE OF DURATION AND DEPTH ON THE DEVELOPMENT OF SYMPTOMS

Hyperventilation is considered an important factor in the development of somatic symptoms or even panic attacks, though its role has recentl y been disputed. Arguments are often based on findings from the so-cal led Hyperventilation Provocation Test (HVPT), which is a procedure con sisting of voluntarily overbreathing. The HVPT has been widely used fo r diagnosing Hyperventilation Syndrome and for experimentally elicitin g panic attacks. Almost no attention, however, has been paid to standa rdizing the test and determining critical values with respect to depth and duration of hyperventilation. In the present study, symptom devel opment was examined in 16 healthy subjects who underwent four HVPTs th at differed in depth of hyperventilation (end-tidal PCO2 < 2.4 kPa or < 1.9 kPa), as well as duration of hyperventilation (2 or 5 min). Both depth and duration appeared to have an independent effect on the deve lopment of symptoms. In the 5-min condition, symptoms appeared mainly within the first 3 min. To be sure that the HVPT is long enough and de ep enough to elicit symptoms in most people, a minimum duration of 3 m in is advised, with end-tidal PCO2 decreasing to at least 1.9 kPa or d ropping well over 50% of baseline.