Cluster Headache: The Peripheral Chemosensitivity as Indicated by the Single-Breath CO2 Test

SYNOPSIS
A single-breath CO₂ test was carried out in cluster headache patients both during bout and remission, and in matchedhealthy individuals (n = 10 for each group) to assess peripheral chemosensitivity. The test subjects inhaled one tidal breath of13% CO₂ in air. The response was expressed as the maximal increase in inspiratory minute ventilation (V_I) within 20 secondsfrom the exposure to CO₂, divided by the increase in end-tidal PCO₂ (P_ETCO₂) (the difference in PCO₂ between the testbreath and the preceding control breaths): DV_I/DP_ETCO₂.
Under the initial resting condition, cluster headache patients within the bout showed a slight hyperventilation in that therewas a significantly reduced P_ETCO₂ (P < 0.05, Student's paired t-test), and during remission, higher V_I, and a lower P_ETCO₂ (P < 0.05, Wilcoxon signed rank test), in comparison with the controls. There was no statistically significantdifference as regards the peripheral chemosensitivity between cluster headache and control groups. These results indicatethat cluster headache patients have an intact and properly-functioning carotid body.