title: Relation of concavity in the expiratory flow-volume loop to dynamic hyperinflation during exercise in COPD.
abstract: Active expiration during exercise can increase intrathoracic pressure yielding concavity in the expiratory flow-volume loop in COPD. We investigated the relationship between this concavity and dynamic hyperinflation (DH). 17 COPD patients (FEV1: 38±10%pred, GOLD stage 3-4) and 12 healthy subjects performed cycle ergometer incremental exercise. Expiratory limb of the spontaneous flow-volume loop was analyzed breath-by-breath using a geometric approach (rectangular area ratio (RAR), Respir. Med., 104(3):389-96, 2010). RAR below 0.5 demonstrates expiratory limb concavity. DH was determined with serial inspiratory capacity maneuvers. 5 of 17 patients displayed little end-exercise concavity (RAR=0.52±0.04, group LCONC). 12 patients had concavity at rest and end-exercise RAR reached 0.40±0.03 (group HCONC). Healthy subjects showed no concavity. End-exercise RAR correlated with resting FEV1%pred (R2=0.81, P<0.05). Group HCONC, compared to groups LCONC and H, reached significantly lower work rate, minute ventilation, and more dyspnea. DH inversely correlated with RAR (R2=0.81, P<0.05). Detection of concavity in spontaneous flow-volume loops may help assess DH and exercise limitation in COPD.
authors: Department of Pulmonology, University of Szeged, Deszk, Hungary; Department of Pulmonary Rehabilitation, National Koranyi Institute for TB and Pulmonology, Budapest, Hungary.
authors: Janos
authors: J
authors: Varga
authors: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA. Electronic address: casaburi@ucla.edu.
authors: Richard
authors: R
authors: Casaburi
authors: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.
authors: Shuyi
authors: S
authors: Ma
authors: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.
authors: Ariel
authors: A
authors: Hecht
authors: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.
authors: David
authors: D
authors: Hsia
authors: Department of Pulmonology, University of Szeged, Deszk, Hungary.
authors: Attila
authors: A
authors: Somfay
authors: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.
authors: Janos
authors: J
authors: Porszasz
mesh_terms: D000368:Aged; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012129:Respiratory Function Tests; D013223:Statistics as Topic; D013997:Time Factors
keywords: Chronic obstructive pulmonary disease; Dynamic hyperinflation; Exercise tolerance; Flow-volume loop; Rectangular area ratio