Treatment of patients with lung cancer and severe emphysema: lessons from lung volume reduction surgery

Theoretical diagnosis of emphysema by aerosol bolus inhalation

BACKGROUND

The present contribution deals with the theoretical description of aerosol bolus dispersion in lungs being affected by different manifestations of emphysema. The work constructs the hypothesis that each manifestation of emphysema exhibits specific properties with regard to the dispersion of inhaled and exhaled aerosol boluses as well as the deposition of particles from the aerosol pulse.

METHODS

For an appropriate simulation of single emphysematous manifestations, a previously developed model assuming (I) a random variation of alveolar diameters, (II) an exact localization of diseased structures, and (III) a realistic balance between alveolar air volume and number of air sacs was applied. Dispersion of inhaled and exhaled aerosol boluses was simulated by using the mathematical concept of effective diffusivities. Computations were conducted for an average adult lung (FRC =3,300 mL), symmetric breath-cycles with a length 8 s, and inhalation flow rates of 250 mL/s. Particles used for the model predictions had a uniform diameter of 0.84 µm and a density of 1 g/cm³.

RESULTS

According to the theoretical data obtained from the model highest aerosol bolus dispersion may be observed in lungs affected by panacinar and bullous emphysema, whereas centriacinar and paraseptal emphysema cause a significant reduction of the phenomenon. Also other statistical parameters exhibit partly remarkable differences among the studied manifestations. Particle deposition in lungs affected by bullous emphysema falls below that of lungs impaired by the other types of emphysema by 2%-50%.

CONCLUSIONS

From the hypothetical results presented in this study it may be concluded that aerosol bolus inhalation bears a certain potential for the diagnosis of emphysematous structures and, if applied with sufficient accuracy, also for the distinction of single manifestations of emphysema. For a successful use of the technique, however, all statistical bolus parameters and particle deposition have to be subjected to a detailed evaluation.

Stochastic simulation of alveolar particle deposition in lungs affected by different types of emphysema

In the present study, disease-specific stochastic models were developed for the computation of particle deposition in lungs affected by COPD, emphysema, or both, distinguishing between four types of pulmonary emphysema-centriacinar, paraseptal, panacinar, and bullous. To simulate COPD, airway calibers of the tracheobronchial tree were randomly reduced between 20% and 50% in each airway. For the study of pure COPD ("blue bloaters"), alveolated airway dimensions of the healthy lung were used, while for the simulation of emphysema without COPD ("pink puffers"), normal conductive airway diameters were assumed. Deposition calculations in diseased lungs were carried out by assuming (a) identical inspiration and expiration times (no breath-hold time) and (b) a continuous increase of the functional residual capacity (from 3,300 to 5,000 mL), accompanied by a simultaneous drop of the tidal volume (from 1,000 to 500 mL). Independent of particle size, total alveolar deposition in emphysematous lungs was significantly decreased relative to normal lungs. In particular, the deposition maximum at large particle sizes, which is a characteristic for healthy subjects, completely disappeared. Among the various emphysema models, deposition was smallest in lungs with bullous emphysema due to strongly enhanced settling and diffusion distances within the alveolar structures. A change of the lung volume caused a further decrease in particle deposition. Alveolar deposition in "blue bloaters" and "pink puffers" was very similar to the deposition in patients suffering from COPD and emphysema. Alveolar deposition per acinar airway generation was also strongly reduced in diseased lungs compared to normal lungs. Besides this reduction, deposition patterns became more uniform throughout the alveolar region.

Management strategies for the solitary pulmonary nodule

PURPOSE OF REVIEW

The challenge of diagnosis and management of solitary pulmonary nodules is among the most common yet most important areas of pulmonary medicine. Ideally, the goal of diagnosis and management is to promptly bring to surgery all patients with operable malignant nodules while avoiding unnecessary thoracotomy in patients with benign disease.

RECENT FINDINGS

Effective management of the solitary pulmonary nodule depends upon an understanding of decision analysis principles so that diverse technologies can be integrated into a systematic approach.

SUMMARY

In almost all patients computed tomography (CT) is the best first step. Three key questions can then help guide the workup of the SPN. These are what is the pretest probability of cancer, what is the risk of surgical complications, and does the appearance of the nodule on CT scan suggest a benign or malignant etiology. In patients with average surgical risk, positron emission tomography (PET) scan is warranted when there is discordance between pretest probability of cancer and the appearance of the nodule on CT scan. Thus, when either the patient has a low risk of cancer and the CT suggests a malignant origin, or when there is high risk of cancer and the CT appears benign, PET scan will be cost effective. In most other situations, PET scanning is only marginally more effective than CT and fine needle aspiration strategies but costs much more.

Operative techniques for lung volume reduction surgery

Recently, LVRS has received renewed public interest. Various surgical approaches and techniques exist, and each has challenges, advantages, and disadvantages. Stapled techniques have been used more commonly than plication techniques or lasers. The choice of staple buttressing material has not been shown to affect outcome. For most patients who are suitable for LVRS, a bilateral procedure is appropriate. Minimally invasive techniques are gaining in popularity and have demonstrated good results. Of the approaches discussed above, bilateral thoracoscopy in the supine position is likely to be the most expeditious with the lowest incision-related morbidity and dysfunction.