Journal of Applied Physiology, Vol 67, Issue 6 2622-2626, Copyright © 1989 by American Physiological Society
Airways responsiveness determined by consecutive histamine challenges in asymptomatic asthmatics
M. Kung, G. C. Scott and N. K. Burki
Department of Medicine, College of Medicine, University of Kentucky, Lexington 40536.
The effect of two consecutive histamine inhalation challenges on airways
responsiveness was assessed in a group of eight nonsmoking nonmedicated
asthmatics aged 19-27 yr. All subjects had a base-line forced expiratory
volume in 1 s (FEV1) of greater than 80% of their predicted normal value
before the initial challenge and were allowed to recover to greater than
95% of the initial base-line FEV1 value before the second challenge was
initiated. The average airways recovery time after the first challenge was
44 min but ranged between 30 and 90 min. The mean +/- SD values of
cumulative histamine dose units provoking a 20% decrease of the FEV1 from
the buffer control value (PD20FEV1) were 10.79 +/- 5.95 determined with the
first and 30.50 +/- 46.36 with the second challenge (P greater than 0.05).
We conclude that sequential histamine challenges performed in mild
asthmatics with closely controlled prechallenge airways function are well
tolerated. Although some variance does exist in intersubject airways
recovery time and in intra-subject histamine airways responsiveness
determined by sequential challenges, our data do not support recent
observations (J. Appl. Physiol. 63: 1572-1577, 1987) that histamine
tolerance is a characteristic finding associated with bronchial asthma.
