Nijmegen score and hyperventilation Test
A Nijmegen score ≥ 23 was considered positive.
The HVT was performed by a single operator and consisted of making the patient hyperventilate at a respiratory rate of 30 per min for a period of 3 min. The partial pressure of CO2 at the end of expiration (PETCO2) was measured continuously throughout the test using a capnograph. The basal PETCO2 at the start of the test and the minimum PETCO2 attained after the hyperventilation phase were measured. The symptoms reproduced were recorded after the hyperventilation phase (anxiety, paresthesia or tingling, dizziness, headache, visual blurring, chest tightness or pain, palpitations, ankylosis of the extremities or cold extremities, confusion, and cough). The duration of the return to the initial baseline PETCO2 was then determined. The HVT was considered positive if at least two of the following three criteria were present:
A positive HVT confirmed the diagnosis of HVS.