title: Forced expiratory capnography and chronic obstructive pulmonary disease (COPD).
abstract: This report proposes a potentially sensitive and simple physiological method to detect early changes and to follow disease progression in obstructive pulmonary disease (COPD) based upon the usual pulmonary function test. Pulmonary function testing is a simple, although relatively insensitive, method to detect and follow COPD. As a proof-of-concept, we have examined the slope of the plateau for carbon dioxide during forced expiratory capnography in healthy (n = 10) and COPD subjects (n = 10). We compared the change in the rate of exhalation of carbon dioxide over time as a marker of heterogeneous ventilation of the lung. All subjects underwent pulmonary function testing, body-plethysmography, and forced exhalation capnography. The subjects with COPD also underwent high-resolution computed tomography of the chest. Regression lines were fitted to the slopes of the forced exhalation capnogram curves. There was no difference in the mean levels of exhaled carbon dioxide between the COPD and the healthy groups (p > 0.48). We found a significant difference in the mean slope of the forced exhalation capnogram for the COPD subjects compared to the healthy subjects (p = 0.01). Most important, for the COPD subjects, there was a significant positive correlation between the slope of the forced exhaled capnogram and a defined radiodensity measurement of the lung by high-resolution computed tomography (r(2) = 0.49, p = 0.02). The slope of the forced exhalation capnogram may be a simple way to determine physiological changes in the lungs in patients with COPD that are not obtainable with standard pulmonary function tests. Forced exhalation capnography would be of great clinical benefit if it can identify early disease changes and at-risk individuals.
authors: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA. rbrown@jhsph.edu
authors: Robert H
authors: RH
authors: Brown
authors: Allison
authors: A
authors: Brooker
authors: Robert A
authors: RA
authors: Wise
authors: Curt
authors: C
authors: Reynolds
authors: Claudio
authors: C
authors: Loccioni
authors: Adolfo
authors: A
authors: Russo
authors: Terence H
authors: TH
authors: Risby
mesh_terms: D000328:Adult; D000368:Aged; D019296:Capnography / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism; D016022:Case-Control Studies; D045853:Exhalation / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012720:Severity of Illness Index; D013147:Spirometry; D014057:Tomography, X-Ray Computed; D014797:Vital Capacity / Q000502:physiology
chemical_list: D002245:Carbon Dioxide