Differential diagnosis of chronic airflow obstruction

Effect of emphysema on lung cancer risk in smokers: a computed tomography-based assessment

The contribution of emphysema to lung cancer risk has been recognized, but the effect size needs to be further defined. In this study, 565 primary lung cancer cases were enrolled though a prospective lung cancer cohort at Mayo Clinic, and 450 controls were smokers participating in a lung cancer screening study in the same institution using spiral computed tomography (CT). Cases and controls were frequency matched on age, gender, race, smoking status, and residential region. CT imaging using standard protocol at the time of lung cancer diagnosis (case) or during the study (control) was assessed for emphysema by visual scoring CT analysis as a percentage of lung tissue destroyed. The clinical definition of emphysema was the diagnosis recorded in the medical documentation. Using multiple logistic regression models, emphysema (≥ 5% on CT) was found to be associated with a 3.8-fold increased lung cancer risk in Caucasians, with higher risk in subgroups of younger (<65 years old, OR = 4.64), heavy smokers (≥ 40 pack-years, OR = 4.46), and small-cell lung cancer (OR = 5.62). When using >0% or ≥ 10% emphysema on CT, lung cancer risk was 2.79-fold or 3.33-fold higher than controls. Compared with CT evaluation (using criterion ≥ 5%), the sensitivity, specificity, positive and negative predictive values, and the accuracy of the clinical diagnosis for emphysema in controls were 19%, 98%, 73%, 84%, and 83%, respectively. These results imply that an accurate evaluation of emphysema could help reliably identify individuals at greater risk of lung cancer among smokers.

Evaluation of obstructive lung disease with vibration response imaging

As optimal treatment and prognosis differ between asthma and COPD, a new diagnostic approach to differentiating between the two disorders would be clinically desirable. We evaluated the utility of vibration response imaging in differentiating between asthma and COPD. Sixty-six subjects with asthma or COPD were recorded, before and after the administration of a short-acting bronchodilator, using a computerized lung sound analysis device. Gray-scale images of breath sound distribution in the lungs, quantitative data in breath sound graphs (timing, amplitude) and automatic crackle and wheeze detection programs were used to differentiate between asthma and COPD subjects. Imaging data were compared with the clinical diagnosis, made by the standard methods (medical history, physical examination, and spirometric indices). Blinded evaluation of images demonstrated a significantly higher rate of improvement in image dynamics, shape and overall improvement following bronchodilator in subjects with asthma compared with those with COPD. Quantitative data showed distinct patterns in timing and amplitude for these two pathologies. Combined analyses based on qualitative image evaluation and quantitative data demonstrated an overall 85% accuracy (84% for asthma, 86% for COPD) in differentiating between asthma and COPD. Combined qualitative and quantitative evaluations of lung sounds are quite sensitive in distinguishing between lung sound recordings of COPD and asthma individuals. Lung sound features of synchronization in timing and intensity provide objective data that may further differentiate these two airway disorders.

Patient selection for lung volume reduction surgery

LVRS represents a valid surgical option for a limited number of patients who have symptomatic emphysema. The results of recent controlled studies have provided a realistic view of LVRS outcomes and yielded a validated algorithm for selection of optimal candidates for surgery. Furthermore, the NETT has provided simultaneously collected cost data that have provided a unique view of the costs and benefits of LVRS in patients who have advanced emphysema. Additional data collection will better define the long-term benefits of such surgical intervention in patients who have COPD.

Expression of bronchodilator response: comparison of four indices

Several indices have been suggested to express the bronchodilator response but there is no agreement on what is the ideal expression. The forced expiratory volume in I s (FEV1) was measured in 190 patients of bronchial asthma before and after inhalation of 200 micrograms salbutamol. Four different indices of bronchodilator response were calculated. The change in FEV1 was expressed as absolute value (delta FEV1), as a percentage of initial FEV1 (delta FEV1% initial), as a percentage of the predicted normal value (delta FEV1% predicted) and as a percentage of maximum achievable reversibility, i.e. the difference between predicted and initial values (delta FEV1% [predicted-initial]). A significant negative correlation was observed between delta FEV1 initial and initial FEV1% predicted (r = -0.33, P < 0.0001) but not delta FEV1 and initial FEV1% predicted, or between delta FEV1% predicted and initial FEV1% predicted. The values of delta FEV1% [predicted-initial] tended to reach towards infinity as the initial FEV1% predicted approached 100%. delta FEV1% predicted had similar sensitivity but greater specificity than delta FEV1% initial in detecting a true bronchodilator response. It was concluded that being dependent on the initial value, delta FEV1% initial was not an appropriate method to express the bronchodilator response. Although all other methods had limitations, delta FEV1 and delta FEV1% predicted appeared to be better indices.

Obstructive lung diseases: COPD, asthma, and many imitators

Chronic obstructive pulmonary disease (COPD) is a common respiratory disorder that occurs in 10% to 15% of people who smoke, an estimated 16 million Americans. Asthma is also common. Spirometry is generally used to detect early COPD in smokers and to evaluate patients with respiratory symptoms. Although COPD and asthma account for most obstructive lung diseases, a broad spectrum of other disorders, including bronchiectasis, upper airway lesions, bronchiolar diseases, and some interstitial lung diseases, are associated with airflow obstruction. These less common forms of obstructive lung diseases are often misdiagnosed because of their uncommon occurrence and poor recognition. We describe the heterogeneous spectrum of disorders that can present with evidence of airflow obstruction and outline a diagnostic approach to obstructive lung disease.

Lung volume reduction surgery for emphysema

Over the past decades, extensive literature has been published regarding surgical therapies for advanced COPD. Lung-volume reduction surgery would be an option for a significantly larger number of patients than classic bullectomy or lung transplantation. Unfortunately, the initial enthusiasm has been tempered by major questions regarding the optimal surgical approach, safety, firm selection criteria, and confirmation of long-term benefits. In fact, the long-term follow-up reported in patients undergoing classical bullectomy should serve to caution against unbridled enthusiasm for the indiscriminate application of LVRS. Those with the worst long-term outcome despite favourable short-term improvements after bullectomy have consistently been those with the lowest pulmonary function and significant emphysema in the remaining lung who appear remarkably similar to those being evaluated for LVRS. With this in mind, the National Heart, Lung and Blood Institute partnered with the Health Care Finance Administration to establish a multicenter, prospective, randomized study of intensive medical management, including pulmonary rehabilitation versus the same plus bilateral (by MS or VATS), known as the National Emphysema Treatment Trial. The primary objectives are to determine whether LVRS improves survival and exercise capacity. The secondary objectives will examine effects on pulmonary function and HRQL, compare surgical techniques, examine selection criteria for optimal response, identify criteria to determine those who are at prohibitive surgical risk, and examine long-term cost effectiveness. It is hoped that data collected from this novel, multicenter collaboration will place the role of LVRS in a clearer perspective for the physician caring for patients with advanced emphysema.