A bulla is defined as an air space in the lung measuring more than one centimeter in diameter in the distended state; the term giant bulla is used for bullae that occupy at least 30 percent of a hemithorax [1-3]. A single giant bulla may be surrounded by normal lung tissue or may be accompanied by a number of smaller adjacent bullae. Bullectomy involves the surgical removal of one or more giant bullae to improve symptoms and respiratory function in patients with bullous emphysema [4,5].
The indications and contraindications for bullectomy, as well as the perioperative management and operative technique of bullectomy will be reviewed here. The evaluation and medical management of giant bullae in patients with chronic obstructive pulmonary disease (COPD) and the roles of lung volume reduction surgery and lung transplantation in the management of advanced COPD are discussed separately. (See "Evaluation and medical management of giant bullae in COPD" and "Lung volume reduction surgery in COPD" and "Lung transplantation: General guidelines for recipient selection".)
Giant bullae adversely affect respiratory physiology in several ways. They occupy a large volume of the chest cavity and compress adjacent, more normal lung tissue. The compressed areas have reduced aeration and reduced elastic recoil. In addition, giant bullae can exert pressure on the diaphragm, leading to a flatter and less efficient shape. During exercise, bullae that communicate with the tracheobronchial tree increase in size due to dynamic hyperinflation and further impair respiratory function. (See "Dynamic hyperinflation in patients with COPD", section on 'Pathophysiology'.)
The proposed mechanisms by which excising a giant bulla and relieving lung compression improve lung function include [5-7]:
- Reducing the size mismatching between the hyperinflated lungs and the chest cavity, which restores the outward circumferential pull on the bronchioles (ie, increases elastic recoil).
- With improved elastic recoil, airway resistance is decreased and expiratory airflow improved, thus reducing air trapping.
- Removing the space occupying effect of the bulla and reducing air trapping help to restore the diaphragm to a more domed shape, which is more efficient.
- Reinflation of compressed areas decreases the physiologic dead space that was caused by compression of normal lung by the inflated bulla and improves matching of ventilation and perfusion.
- Reducing airway resistance, air trapping, and physiologic dead space decreases the work of breathing.