Ventilation-perfusion mismatch after methacholine challenge in patients with mild bronchial asthma.
To investigate the effects of methacholine (MTH) challenge on spirometry, lung mechanics, respiratory gases, and ventilation-perfusion (VA/Q) distributions, 16 subjects 16 to 58 yr of age with stable mild asthma (FEV1, 92 +/- 5% [SEM] predicted; FEF25-75, 71 +/- 7% predicted; respiratory system resistance (Rrs) at 4 Hz, 4.6 +/- 0.4 cm H2O/L-1 s; PaO2, 88 +/- 3 mm Hg; AaPO2, 23 +/- 3 mm Hg) were recruited. Baseline VA/Q distributions were unimodal and relatively narrow in 12 patients and modestly bimodal in the other four. The dispersion of pulmonary blood flow (log SD Q) was slightly enlarged (0.71 +/- 0.09) and that of ventilation (log SD V) was normal (0.57 +/- 0.04) (normal range, 0.3 to 0.6); an index of overall VA/Q heterogeneity (DISP R-E*) was also mildly abnormal (5.3 +/- 0.8) (normal values less than 3.0). After MTH challenge, FEV1, FEF25-75, and PaO2 fell (to 62 +/- 3 and 35 +/- 3% predicted, and to 71 +/- 1 mm Hg, respectively), whereas Rrs (p less than 0.001 each), minute ventilation (p less than 0.02), heart rate (p less than 0.01), and AaPO2 increased (p less than 0.001). VA/Q relationships mildly to moderately worsened (log SD Q increased to 0.98 +/- 0.04 [p less than 0.01], log SD V to 0.79 +/- 0.04, and DISP R-E* to 9.8 +/- 0.6 [p less than 0.001 each]). Qualitatively, the pattern of blood flow distribution was broadly unimodal in 13 patients and modestly bimodal in three, of whom only one had a bimodal baseline distribution.(ABSTRACT TRUNCATED AT 250 WORDS)
Rodriguez-Roisin
R
R
Servei de Pneumologia, Hospital Clinic, Facultat de Medicina, Universitat de Barcelona, Spain.
Ferrer
A
A
Navajas
D
D
Agusti
A G
AG
Wagner
P D
PD
Roca
J
J
D000293:Adolescent; D000328:Adult; D000420:Albuterol / Q000494:pharmacology; D001249:Asthma / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008450:Maximal Midexpiratory Flow Rate / Q000187:drug effects; D016210:Methacholine Chloride; D008875:Middle Aged; D011652:Pulmonary Circulation / Q000187:drug effects; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D013997:Time Factors; D014692:Ventilation-Perfusion Ratio / Q000187:drug effects
D016210:Methacholine Chloride; D000420:Albuterol