Am. J. Respir. Crit. Care Med., Volume 164, Number 2, July 2001, 216-218

Airway Narrowing Associated with Inhibition of Deep Inspiration during Methacholine Inhalation in Asthmatics

GREGORY G. KING, BARBARA J. MOORE, CHUN Y. SEOW, and PETER D. PARÉ

University of British Columbia McDonald Research Laboratories and the i-CAPTURE Center, St. Paul's Hospital, Vancouver, British Columbia, Canada; Institute of Respiratory Medicine, University of Sydney, Sydney, Australia; and Department of Anatomy and Department of Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada

Reduced bronchodilatation in response to deep inspiration (DI) has been demonstrated in asthmatics. We have previously shown that inhibition of DI for 10 min or more during methacholine inhalation increases airway narrowing in normals. We tested the hypothesis that inhibition of DIs during methacholine inhalation in asthmatics would not affect the magnitude of airway narrowing. We administered the PC₁₅ dose of methacholine to eight asthmatics every 5 min for 5 doses and measured spirometry after each dose. On four separate days, subjects received either 2, 3, 4, or 5 doses selected randomly, but DIs were inhibited during the challenge and spirometry was measured only at the start and after the final dose. Geometric mean PC₁₅ was 1.6 mg/ml. Mean values for FEV₁ (± SEM) after Doses 2 through 5 were 84 ± 4, 78 ± 6, 79 ± 5, and 81 ± 3% of baseline, respectively, when DIs were allowed. During inhibition of DIs, they were 73 ± 6, 67 ± 5, 64 ± 6, and 61 ± 7% of baseline values. Decreases in FEV₁ after Doses 4 and 5 were significantly greater when DIs were inhibited (p < 0.05). We conclude that in this group of asthmatics, inhibition of DI for 15 min is associated with increased airway narrowing in response to methacholine inhalation, and therefore, DI may be an important factor limiting induced airway narrowing in asthmatics as well as in normal subjects.

This article has been cited by other articles:

				S. S. An, T. R. Bai, J. H. T. Bates, J. L. Black, R. H. Brown, V. Brusasco, P. Chitano, L. Deng, M. Dowell, D. H. Eidelman, et al. Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma Eur. Respir. J., May 1, 2007; 29(5): 834 - 860. [Abstract] [Full Text] [PDF]

				N. Scichilone, S. Permutt, V. Bellia, and A. Togias Inhaled Corticosteroids and the Beneficial Effect of Deep Inspiration in Asthma Am. J. Respir. Crit. Care Med., September 15, 2005; 172(6): 693 - 699. [Abstract] [Full Text] [PDF]

				G.G. King, J.D. Carroll, N.L. Muller, K.P. Whittall, M. Gao, Y. Nakano, and P.D. Pare Heterogeneity of narrowing in normal and asthmatic airways measured by HRCT Eur. Respir. J., August 1, 2004; 24(2): 211 - 218. [Abstract] [Full Text] [PDF]

				N. Scichilone, R. Marchese, F. Catalano, A. M. Vignola, A. Togias, and V. Bellia Bronchodilatory Effect of Deep Inspiration Is Absent in Subjects With Mild COPD Chest, June 1, 2004; 125(6): 2029 - 2035. [Abstract] [Full Text] [PDF]

				M. J. TOBIN Asthma, Airway Biology, and Nasal Disorders in AJRCCM 2001 Am. J. Respir. Crit. Care Med., March 1, 2002; 165(5): 598 - 618. [Full Text] [PDF]

				J. Latourelle, B. Fabry, and J. J. Fredberg Dynamic equilibration of airway smooth muscle contraction during physiological loading J Appl Physiol, February 1, 2002; 92(2): 771 - 779. [Abstract] [Full Text] [PDF]