Km. Hurwitz et al., REFRACTORY PERIOD DURING PROVOCATION WITH EUCAPNIC HYPERVENTILATION AND METHACHOLINE, American journal of respiratory and critical care medicine, 149(6), 1994, pp. 1452-1456
Citations number
29
Categorie Soggetti
Emergency Medicine & Critical Care","Respiratory System
Eucapnic voluntary hyperventilation (EVH) and methacholine inhalation
challenge (MIC) both cause bronchoconstriction in asthmatics. A refrac
tory period, or time when the response to bronchoprovocation in a seri
es of challenges is diminished, has been found after hyperventilation
or exercise but not after MIC. We investigated whether EVH or MIC blun
ted the response to the other test. Sixteen asthmatics were studied on
2 d, taking both tests each day. They were randomized to either EVH o
r MIV first on Day 1, then the opposite order on Day 2, 6 to 14 d apar
t. After EVH as a first test, the mean decline in FEV(1) from base-lin
e was 18.66 +/- 4.76% (mean +/- SEM), but when EVH followed MIC, the r
esponse to EVH was reduced by 30%, to a decline in FEV(1) of only 13.0
2 +/- 3.75% (p = 0.0026). During MIC, the mean provocation dose to cau
se 20% decrease in FEV(1) (PD20) given as the initial challenge was 54
.77 +/- 21.60 breath units, compared with 46.94 +/- 19.55 breath units
when MIC followed EVH (p = 0.54). However, the subset of patients mos
t sensitive to methacholine (PD20 < 0.1 breath unit) had changes sugge
stive of a refractory period after EVH, with a mean increase in the PD
20 from 0.06 +/- 0.01 to 3.35 +/- 1.43 (p = 0.069). Our data show that
MIC attenuates the response to subsequent challenge with EVH. Convers
ely, EVH may only affect subsequent MIC in those most sensitive to met
hacholine.