title: Severity grading of chronic obstructive pulmonary disease: the confounding effect of phenotype and thoracic gas compression.
abstract: Current guidelines recommend severity of chronic obstructive pulmonary disease be graded by using forced expiratory volume in 1 s (FEV1). But this measurement is biased by thoracic gas compression depending on lung volume and airflow resistance. The aim of this study was to test the hypothesis that the effect of thoracic gas compression on FEV1 is greater in emphysema than chronic bronchitis because of larger lung volumes, and this influences severity classification and prognosis. FEV1 was simultaneously measured by spirometry and body plethysmography (FEV1-pl) in 47 subjects with dominant emphysema and 51 with dominant chronic bronchitis. Subjects with dominant emphysema had larger lung volumes, lower diffusion capacity, and lower FEV1 than those with dominant chronic bronchitis. However, FEV1-pl, patient-centered variables (dyspnea, quality of life, exercise tolerance, exacerbation frequency), arterial blood gases, and respiratory impedance were not significantly different between groups. Using FEV1-pl instead of FEV1 shifted severity distribution toward less severe classes in dominant emphysema more than chronic bronchitis. The body mass, obstruction, dyspnea, and exercise (BODE) index was significantly higher in dominant emphysema than chronic bronchitis, but this difference significantly decreased when FEV1-pl was substituted for FEV1. In conclusion, the FEV1 is biased by thoracic gas compression more in subjects with dominant emphysema than in those with chronic bronchitis. This variably and significantly affects the severity grading systems currently recommended.
authors.affiliation: Allergologia e Fisiopatologia Respiratoria, ASO S. Croce e Carle, Cuneo, Italy;
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pellegrino
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Università di Genova, Genova, Italy;
authors.forename: Emanuele
authors.initials: E
authors.lastname: Crimi
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy;
authors.forename: Alessandro
authors.initials: A
authors.lastname: Gobbi
authors.affiliation: Laboratorio di Fisiopatologia Respiratoria e Centro Disturbi Respiratori nel Sonno, Ospedale S. Luigi, Orbassano, Torino, Italy;
authors.forename: Roberto
authors.initials: R
authors.lastname: Torchio
authors.affiliation: Allergologia e Fisiopatologia Respiratoria, ASO S. Croce e Carle, Cuneo, Italy;
authors.forename: Andrea
authors.initials: A
authors.lastname: Antonelli
authors.affiliation: Malattie Apparato Respiratorio, Ospedale S. Luigi, Orbassano, Torino; and.
authors.forename: Carlo
authors.initials: C
authors.lastname: Gulotta
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Università di Genova, Genova, Italy;
authors.forename: Michele
authors.initials: M
authors.lastname: Baroffio
authors.affiliation: Unità Respiratoria, Ospedale San Paolo, Università degli Studi di Milano, Milano, Italy.
authors.forename: Giuseppe Francesco Sferrazza
authors.initials: GF
authors.lastname: Papa
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy;
authors.forename: Raffaele
authors.initials: R
authors.lastname: Dellacà
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Università di Genova, Genova, Italy; vito.brusasco@unige.it.
authors.forename: Vito
authors.initials: V
authors.lastname: Brusasco
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008875:Middle Aged; D010641:Phenotype; D010993:Plethysmography, Whole Body / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods*; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014109:Total Lung Capacity
keywords: chronic bronchitis; emphysema; forced expiratory volume in 1 s; plethysmography