Relationship between quasi-static pulmonary hysteresis and maximal airway narrowing in humans.
Two groups of subjects were studied: one with (group 1: 5 healthy and 4 mildly asthmatic subjects) and another without (group 2:9 moderately and severely asthmatic subjects) a plateau of response to methacholine (MCh). We determined the effect of deep inhalation by comparing expiratory flows at 40% of forced vital capacity from maximal and partial flow-volume curves (MEF40M/P) and the quasi-static transpulmonary pressure-volume (Ptp-V) area. In group 1, MEF40M/P increased from 1.58 +/- 0.23 (SE) at baseline up to a maximum of 3.91 +/- 0.69 after MCh when forced expiratory volume in 1 s (FEV1) was decreased on plateau by 24 +/- 2%. The plateau of FEV1 was always paralleled by a plateau of MEF40M/P. In group 2, MEF40 M/P increased from 1.58 +/- 0.10 at baseline up to a maximum of 3.48 +/- 0.26 after MCh when FEV1 was decreased by 31 +/- 3% and then decreased to 2.42 +/- 0.24 when FEV1 was decreased by 46 +/- 2%. Ptp-V area was similar in the two groups at baseline yet was increased by 122 +/- 9% in group 2 and unchanged in group 1 at MCh end point. These findings suggest that the increased maximal response to MCh in asthmatic subjects is associated with an involvement of the lung periphery.
Brusasco
V
V
Servizio di Fisiopatologia Respiratoria, Ospedale A. Carle, Cuneo, Italy.
Pellegrino
R
R
Violante
B
B
Crimi
E
E
D000328:Adult; D001249:Asthma / Q000503:physiopathology; D016084:Bronchoconstriction / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000502:physiology*; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology
D016210:Methacholine Chloride