title: Quantifying the shape of maximal expiratory flow-volume curves in healthy humans and asthmatic patients.
abstract: Differences in the absolute flow and volume of maximal expiratory flow-volume (MEFV) curves have been studied extensively in health and disease. However, the shapes of MEFV curves have received less attention. We questioned if the MEFV curve shape was associated with (i) expiratory flow limitation (EFL) in health and (ii) changes in bronchial caliber in asthmatics. Using the slope-ratio (SR) index, we quantified MEFV curve shape in 84 healthy subjects and 8 matched asthmatics. Healthy subjects performed a maximal exercise test to assess EFL. Those with EFL during had a greater SR (1.15 ± 0.20 vs. 0.85 ± 0.20, p<0.05) yet, there was no association between maximal oxygen consumption and SR (r=0.14, p>0.05). Asthmatics average SR was greater than the healthy subjects (1.35 ± 0.03 vs. 0.90 ± 0.11, p<0.05), but there were no differences when bronchial caliber was manipulated. In conclusion, a greater SR is related to EFL and this metric could aid in discriminating between groups known to differ in the absolute size of MEFV curves.
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada. Electronic address: p.dominelli@alumni.ubc.ca.
authors.forename: Paolo B
authors.initials: PB
authors.lastname: Dominelli
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Molgat-Seon
authors.affiliation: Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Foster
authors.affiliation: University of British Columbia Division of Respiratory Medicine, Kelowna General Hospital, Kelowna, BC, Canada.
authors.forename: Giulio S
authors.initials: GS
authors.lastname: Dominelli
authors.affiliation: Department of Environmental & Health Sciences, Johnson State College, Johnson, VT, United States.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Haverkamp
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: William R
authors.initials: WR
authors.lastname: Henderson
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: A William
authors.initials: AW
authors.lastname: Sheel
mesh_terms: D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D002317:Cardiovascular Agents / Q000008:administration & dosage; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006371:Helium / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008449:Maximal Expiratory Flow-Volume Curves / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage; D012189:Retrospective Studies; D013147:Spirometry
chemical_list: D002317:Cardiovascular Agents; D006371:Helium; C038949:heliox; D010100:Oxygen
keywords: Expiratory flow limitation; Pulmonary system limitation; Ventilator constraints