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This Article Full Text Full Text (PDF) All Versions of this Article: 106/6/1902    most recent 00085.2009v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Rodríguez-Roisin, R. Articles by Wagner, P. D. PubMed PubMed Citation Articles by Rodríguez-Roisin, R. Articles by Wagner, P. D.

Ventilation-perfusion imbalance and chronic obstructive pulmonary disease staging severity

¹Servei de Pneumologia (Institut del Tòrax), Hospital Clinic, Institut d'Investigacions Biomédiques August Pi i Sunyer, ²Fundació Clinic de Recerca Biomèdica, and ³Ciber Enfermedades Respiratorias, Universitat de Barcelona, Barcelona, Spain; and ⁴Division of Physiology, University of California, San Diego, California

Submitted 28 January 2009 ; accepted in final form 9 April 2009

Chronic obstructive pulmonary disease (COPD) is characterized by a decline in forced expiratory volume in 1 s (FEV₁) and, in many advanced patients, by arterial hypoxemia with or without hypercapnia. Spirometric and gas exchange abnormalities have not been found to relate closely, but this may reflect a narrow range of severity in patients studied. Therefore, we assessed the relationship between pulmonary gas exchange and airflow limitation in patients with COPD across the severity spectrum. Ventilation-perfusion (_A/) mismatch was measured using the multiple inert gas elimination technique in 150 patients from previous studies. The distribution of patients according to the GOLD stage of COPD was: 15 with stage 1; 40 with stage 2; 32 with stage 3; and 63 with stage 4. In GOLD stage 1, AaPO₂ and _A/ mismatch were clearly abnormal; thereafter, hypoxemia, AaPO₂, and _A/ imbalance increased, but the changes from GOLD stages 1–4 were modest. Postbronchodilator FEV₁ was related to Pa_O2 (r = 0.62) and Pa_CO2 (r = –0.59) and to overall _A/ heterogeneity (r = –0.48) (P < 0.001 each). Pulmonary gas exchange abnormalities in COPD are related to FEV₁ across the spectrum of severity. _A/ imbalance, predominantly perfusion heterogeneity, is disproportionately greater than airflow limitation in GOLD stage 1, suggesting that COPD initially involves the smallest airways, parenchyma, and pulmonary vessels with minimal spirometric disturbances. That progression of _A/ inequality with spirometric severity is modest may reflect pathogenic processes that reduce both local ventilation and blood flow in the same regions through airway and alveolar disease and capillary involvement.

airflow limitation; arterial blood gases; chronic respiratory failure; global initiative for COPD; pulmonary gas exchange