Gj. Argyros et al., THE REFRACTORY PERIOD AFTER EUCAPNIC VOLUNTARY HYPERVENTILATION CHALLENGE AND ITS EFFECT ON CHALLENGE TECHNIQUE, Chest, 108(2), 1995, pp. 419-424
To evaluate whether there is a refractory period (RP) after hyperventi
lation challenge, we compared the bronchoconstrictive response to repe
titive eucapnic voluntary hyperventilation challenge with dry, room te
mperature air (EVH). The serial challenges were identical with 11 know
n asthmatics hyperventilating for 6 min at a target minute ventilation
of 30 times their FEV(1) measured before either challenge. There was
a significant difference between the mean postchallenge fall in FEV(1)
to the initial EVH challenge (27.4+/-9.8%) and the response to the se
cond EVH challenge (16.1+/-5.9%) (p=0.0001), indicating refractoriness
. We then evaluated whether 6 min of uninterrupted EVH challenge gives
a similar bronchospastic response to that which results from an equiv
alent (by total minute ventilation) interrupted challenge of 2 min of
EVH repeated three times. The mean postchallenge fall in FEV(1) in res
ponse to this interrupted challenge was 18.9+/-10.6%, which was signif
icantly different from the 27.4% fall in response to 6 consecutive min
utes of EVH (p=0.036). This study demonstrates that there is a refract
ory period after repeated EVH challenges and this refractoriness affec
ts the response to interrupted, or dosed, EVH challenge.