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:
- PETCO2 at rest or after 5 min of recovery <
30 mmHg
- Time to return to the baseline PETCO2 > 3
min
- Reproduction of more than two symptoms
A positive HVT confirmed the diagnosis of HVS.