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Pulmonary & Critical Care Bulletin
Vol. VII, No. 3, July 15, 2001
In this issue :
From Editor's Desk
Bullous Disease of the lung
Bullous lung disease is defined as the occurrence of bullae in the lung with normal intervening lung parenchyma. Bullous emphysema on the other hand denotes the formation of multiple bullae in the background of diseased lungs (emphysema). Bullae can also occur in stage III sarcoidosis and in vanishing lung disease.
Definition of bulla
Bulla is a large, air containing space within the substance of lung that results from destruction, dilatation and confluence of the air spaces distal to terminal bronchiole. On the other hand, blebs are formed within the layers of visceral pleura.
Etiology and pathogenesis
Bullae are seen more commonly among the smokers and drug abusers, but are also found in patients with fibrosis of the lung (stage III sarcoidosis and pneumoconiosis), and in alpha -1 antitrypsin deficiency state.
Bullae are formed as a result of weakness of the alveolar wall, especially in the lung apices where pleural pressure is more negative. These bullae get filled during inspiration and due to ball-valve like mechanism, air trapping within the bullae occurs.
Usually, patients are asymptomatic with bullous lung disease. Patient can develop progressive dyspnoea and chest pain as a result of rapid increase in the size of the bullae or due to pneumothorax. Chest X-ray shows areas of increased radiolucency sharply delineated by a fine radiopaque line.
CT scan helps in assessing the size, site, number of bullae and condition of the intervening lung.
Pulmonary function testing is used to assess the volume of air trapped in the bulla (volume of air trapped in the bulla = FRC determined by body box - FRC by open circuit method).
Combination of decreased DLCO and decreased elastic recoil pressure favours the diagnosis of widespread emphysema. Infection, pain, haemorrhage, pneumothorax are some of the important complications. Very rarely, lung cancer can develop.
I. Medical treatment : On asymptomatic patient with bullous lung disease, annual chest x-ray should be obtained; asked to quit smoking and avoid competitive sports. If the infection is suspected in the bulla, antibiotics should be used according to gram stain and culture report. If there is no response to adequate medical therapy, surgery should be considered.
2. Surgical treatment: In a patient with localised disease with well preserved lung function, surgery provides symptomatic relief, improves exercise tolerance and improves lung function.
Surgical outcome depends on the size of the bullae (if the size is greater than 50% of hemithorax, the improvement recorded will be maximum). Surgery is indicated in patients with :
a. Large bullae causing dyspnoea
The various surgical approaches used are : median sternotomy, lateral thoracotomy or video assisted thoracoscopic surgery. The bulla is/are either resected (bullectomy), plicated or excised. Sometimes, laser (CO2 or Nd-YAG) is used to cause fibrosis of the bulla. Unilateral/bilateral stapling techniques can be useful.
Lung volume reduction Surgery (LVRS)
This surgical technique is useful in patient with bullous emphysema who are not fit for lung transplantation (or don't meet the criteria) or do badly on medical therapy. In this procedure, about 20-30% of the diseased lung is removed. The qualifying candidates or LVRS are:
i. General: Marked disability before and after completing pulmonary rehabilitation programme; cessation of smoking for more than 6 months; age <75 yrs and able to provide informed consent.
ii. Anatomic (CXR, CT and V/Q scan): Patient with marked hyperinflation and emphysema.
iii. Physiologic : FEV1 <35% of predicted.
Evidence of thoracic hyperinflation in the form of residual volume > 220% of predicted; total lung capacity > 120% of predicted, and TGV > 180% of predicted, DLCO < 50% of predicted, Pa CO2 < 55 and Pa O2 > 55 mm Hg.
LVRS in emphysematous lung disease :
a. Improves elastic recoil pressure of the lung and prevents air trapping.
Future directions for LVRS
1. To wean ventilator dependant COPD
Dr. Dharam Pal, MD, DM
Dr. Dharam Pal, MD, DM
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