Severe Centrilobular Emphysema in a Patient Without Airflow Obstruction

Abstract

To the Editor: Emphysema is a pathologic diagnosis that often accompanies the clinical finding of chronic airflow limitation. Although these two components often coexist, they may not necessarily progress in synchrony. We report a patient with severe smoking-related centrilobular emphysema and hypoxemic respiratory failure, whose pulmonary function was normal except for a low diffusing capacity of the lung for carbon monoxide (Dlco). An 81-year-old white woman, a 30-pack-year ex-smoker, had progressive and marked exertional dyspnea, and resting hypoxemia requiring supplemental oxygen. She was slightly overweight with no chest wall deformity and no clubbing. Breath sounds were normal with no wheezes and only few inspiratory crackles in both bases. There was an accentuated pulmonic component of the second heart sound but no evidence of left- or right-heart failure. Expiratory flow rates were normal (FEV1, 1.3 L[ 108%]; FVC, 2.0 L [107%]). Lung volumes via dilution were all slightly elevated. Dlco was severely reduced, at 4 mL/mm Hg/min (23%). The expiratory flow-volume loop is shown in Figure 1 . Chest radiographic findings were normal. Radionucleotide ventilation-perfusion lung scan findings were low probability for thromboembolism, and ultrasound revealed patent leg veins. Resting room air blood gases showed the following findings: Pao2, 52 mm Hg; Paco2, 37 mm Hg; arterial oxygen saturation, 88%, which decreased to 78% following a brief walk. Hemoglobin level was 16.6 g/dL. High-resolution CT scan (HRCT) showed diffuse centrilobular emphysema, with no bullae or interstitial disease (Fig 2). Home oxygen therapy was continued, and treatment with inhaled bronchodilation was initiated in attempt to improve her dyspnea. She remained in clinically stable condition and was oxygen dependent.Figure 2Representative HRCT slice of lung. Note the diffuse centrilobular emphysema.View Large Image Figure ViewerDownload (PPT) This case is unusual in that emphysema was severe enough to cause marked dyspnea, resting hypoxemia, and a severely reduced Dlco, despite normal chest radiographic findings, normal expiratory flows, and near-normal static lung volumes. Since this is physiologically possible1Gelb A Hogg J Muller N et al.Contribution of emphysema and small airways in COPD.Chest. 1996; 109: 353-359Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar2Nagai A Yamawaki I Takizawa T et al.Alveolar attachments in emphysema of human lungs.Am Rev Respir Dis. 1991; 144: 888-891Crossref PubMed Scopus (28) Google Scholar3Pride N Ingram R Lim T Interaction between parenchyma and airways in chronic obstructive pulmonary disease in asthma.Am Rev Respir Dis. 1991; 143: 1446-1449Crossref Scopus (10) Google Scholar but clinically uncommon, other causes of dyspnea, hypoxemia, and decreased Dlco were considered and excluded. The classic teaching holds that emphysema causes loss of elastic recoil and thereby “functional” airways obstruction. Although emphysematous airspace destruction commonly occurs with airflow obstruction, the two are not interdependent processes.1Gelb A Hogg J Muller N et al.Contribution of emphysema and small airways in COPD.Chest. 1996; 109: 353-359Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar2Nagai A Yamawaki I Takizawa T et al.Alveolar attachments in emphysema of human lungs.Am Rev Respir Dis. 1991; 144: 888-891Crossref PubMed Scopus (28) Google Scholar3Pride N Ingram R Lim T Interaction between parenchyma and airways in chronic obstructive pulmonary disease in asthma.Am Rev Respir Dis. 1991; 143: 1446-1449Crossref Scopus (10) Google Scholar Results of the HRCT of the chest correlate well with histologic emphysema4Klein J Gamsu G Webb W et al.High-resolution CT diagnosis of emphysema in symptomatic patients with normal chest radiographs and isolated low diffusing capacity.Radiology. 1992; 182: 817-821Crossref PubMed Scopus (182) Google Scholar5Gould G Redpath M Ryan M et al.Lung CT density correlates with measurements of airflow limitation and the diffusing capacity.Eur Respir J. 1991; 4: 141-146PubMed Google Scholar and have helped to identify patients with emphysema but not airflow obstruction. To our knowledge, other reported patients have had mild clinical disease, without resting hypoxemia. This patient is unusual because of the severity of her symptoms and hypoxemia, despite normal expiratory airflow. This patient demonstrates that although emphysema and airflow limitation commonly occur together, they are actually separate disease processes.