The pulmonary bleb is a small subpleural collection of air located within the layers of the visceral pleura. Such lesions usually present symptomatically, heralded by a spontaneous pneumothorax. Blebs represent the coalescence of air from small ruptures of terminal alveoli that have dissected through the interstitium to form a small subpleural collection. Lesions that result in spontaneous pneumothorax are located predominantly in the apex of the upper lobe or the apex of the superior segment. Multiple blebs are often identified. Most patients with blebs are without significant underlying lung disease. Pathologically, bleb formation occurs secondary to mechanical stress from increased intrathoracic pressure in the lung tissue that is predisposed to deformation by congenital weakness of the connective tissue. The bleb often forms at the lung apex, where there is increased mechanical stress.1 Surgical therapy thus is oriented to the apex of the lung.
The bulla is a larger (>1 cm) airspace collection that forms within the parenchyma. The bulla has a fibrous wall and remnants of lung parenchyma, as evidenced by septations and fragments of the alveolar septa. A significant bulla usually presents with symptoms of dyspnea; however, patients also may have pneumothorax, infection, or carcinoma. The practical classification of bullous disease separates patients into two primary groups: those with normal underlying lung and a predominant single bulla versus those with diffuse underlying emphysema and very often multiple bullae. A large single bulla that encompasses more than 30% of the hemithorax is defined as a giant bulla.
The physiology of bulla growth is associated with a parenchymal weakness in the lung that fills preferentially with air. Secondarily, the force of elastic recoil in adjacent lung produces retraction of the surrounding lung and further enlargement of the bulla.2 Thus, the adjacent nonbullous lung tissue becomes atelectatic and nonfunctional. Identification and restoration of this potentially normal underlying lung are keys to patient selection and surgical therapy.
General Principles and Patient Selection
Virtually, all operative interventions for blebs, bullae, and giant bullae should now be performed using minimally invasive thoracoscopic techniques.
Operative procedures for bleb resection are primarily indicated secondary to the pneumothorax. Thus, the operative principle involves identification of the pulmonary bleb, stapled resection, and a procedure to increase pleural symphysis. Initial treatment of patients with spontaneous pneumothorax should be nonoperative therapy, with chest tube placement. Smaller percutaneous tubes are now available that may function as well as larger tubes and are less painful for the patient. Swift resolution of the pneumothorax and air leak should follow, permitting rapid removal of the tube. Failure of the pneumothorax or air leak to resolve in 4 to 7 days warrants consideration of operative intervention. Pneumothorax recurs at a rate of 20% to 30% with nonoperative therapy, with the greatest incidence in the first 2 years.3 Patients who present with recurrent pneumothorax should have surgical intervention because the recurrence rate after failure of initial conservative therapy approaches 50%. Occasionally, patients with high-risk occupations, such as pilots and scuba divers, may be considered for surgical resection at initial presentation. This author does not believe any evidence exits to support operative intervention at the initial presentation until the patient has failed conservative therapy. In addition, there is no evidence to support pre-emptive thoracoscopy on the contralateral side that has been unaffected by pneumothorax.
While patients with bulla (single or multiple) may present with pneumothorax or dyspnea, patients with giant bulla are more likely to present with dyspnea alone. Surgical resection with therapy for pleural symphysis should be offered to patients who present with pneumothorax and a previously identified bulla. Patients presenting with dyspnea, however, require careful and deliberate preoperative evaluation to quantify the risks and potential benefits of resection. Determining the extent and viability of compromised nonbullous lung tissue is essential to this evaluation because the primary goal of resection is to return gas exchange to more normal values, improve mechanical pulmonary function, and preserve normal lung parenchyma.
Bullous lesions can be easily approached with thoracoscopy. Studies of bleb resection and pleural abrasion have documented similar results for thoracoscopy and thoracotomy, and the feasibility of giant bulla resection with thoracoscopy is well documented.4–6 In addition to reducing pain in the postoperative interval and permitting a more rapid recovery, thoracoscopy may enhance operative examination of the lung and diaphragm. Essential elements of the horoscopic approach include the use of buttressed stapling lines in patients with bullous disease or giant bulla, port placement that avoids injury to the intercostal nerve bundles, and removal of lung tissue from the chest in a protected specimen bag to avoid seeding of potentially occult carcinoma.
Preoperative assessment of patients presenting with bleb disease and spontaneous pneumothorax may be limited. Presently, however, given the low-dose nature of CT scans, all patients presenting with spontaneous pneumothorax should have CT assessment. In younger patients without risk factors, such as smoking, CT is used to rule out congenital lesions and/or high-risk bilateral blebs or bullae. In older patients or those with a significant smoking history, CT scan of the chest should be performed to rule out possible occult carcinoma or bulla. Patients with any evidence of interstitial lung disease or an inflammatory process also should undergo CT scan evaluation and preoperative assessment to discern any possible predisposing medical conditions, such as lymphangiomyotosis (LAM), sarcoid, and other connective tissue disorders. Patients who are immunocompromised (e.g., by immunosuppression or HIV infection) or who have a high suspicion of Pneumocystis pneumonia or other infectious disease should be investigated and treated before operative intervention.
Female patients with recurrent pneumothorax should be evaluated in regard to the timing of their menstrual cycle to assess the possibility of catamenial pneumothorax. If the patient has had recurrent pneumothoraces or pain associated in a regular manner with their menses, then endometriosis and/or systemic hormonal effects may be an important causative agent in the pneumothorax. This is critically important to determine preoperatively, as the treatments, both medical and surgical, are substantially changed if catamenial pneumothorax is suspected. In patients with catamenial pneumothorax, operative intervention is directed at the diaphragm to rule out fenestration defects.
For surgery to be successful in patients with giant bullae, the atelectatic lung must be able to expand and regain function after resection of the bulla or bullous disease. Thus, patients who have a single giant bulla with relatively normal although atelectatic residual lung are ideal candidates for bullectomy. Unfortunately, most patients with bullous disease also have varying degrees of underlying emphysema and compromised lung parenchyma. Radiographic and physiologic testing is used to quantify the extent and viability of the nonbullous compromised lung tissue to define suitable candidates for bullectomy.7 A CT angiogram may facilitate the identification of lung parenchyma and vasculature that is viable but compressed. Quantitative ventilation/perfusion determination should be used to help quantify hypoperfusion to the target areas of bullectomy and flow to the relatively compressed viable lung tissue. Patients with no evidence of viable lung tissue, the so-called vanishing lung, are not candidates for bullectomy. Patients who experience hypercarbia and hypoxia with exercise have been shown in general to have less benefit.8 However, definitive results are best predicted by anatomy, and ideal anatomy may trump even very low forced expiratory volume in 1 second (FEV1) (e.g., <20%). Diffusing capacity of the lung for carbon monoxide (DLCO) is a predictable reflection of the viability of nonbullous lung tissue, and patients with preserved DLCO tend to have better results.9 Finally, complete cardiopulmonary exercise testing and distance walked in 6 minutes may help to quantitate the preoperative reserve of the patient and further assess the risk of the procedure. Patients undergoing elective surgery should undergo pulmonary rehabilitation and should not be active smokers.
All patients require double-lumen endotracheal intubation for single-lung ventilation. Patients with bullous disease who have underlying emphysema should have an epidural catheter placed preoperatively; ideally, the catheter should be used during the procedure. Patients with emphysema also should undergo bronchoscopy before the endotracheal tube is placed to clear the airway of significant secretions before the procedure. Great care should be taken by the anesthesiologist to avoid high peak airway pressures and barotrauma. This may require permissive hypercapnia as well as tolerance of hypoxemia. It is critical and should be the expectation of the operative team that patients will be extubated in the OR, thus avoiding continued positive-pressure ventilation that exacerbates pulmonary air leak.
Thoracoscopy is ideally suited for the resection of blebs, bullae, and giant bullous disease. All patients should be in the lateral decubitus position and optimally flexed at the hip to maximize rib separation. The superior arm should be supported above the plane of the shoulder to permit access to the chest anterior to the scapula with access to the axillary fold. In general, ports should be placed as far anteriorly as possible to take advantage of the wider intercostal interspaces on the anterior chest wall, thus decreasing torsion injury to the intercostal nerves. I almost never place port access posterior to the scapula. Before the ports are placed, Marcaine and epinephrine should be used for intercostal nerve block to limit the nuisance of blood dripping from the port sites and to enhance pain control. A general depiction of port placement is given below; however, after initial camera port placement, definitive placement of the manipulating port and stapling ports should be directed by the thoracoscopic exploration. This can be done by placing a needle into the chest at the proposed port access sites. An additional caveat: Lung tissue that is not intended for resection should never be grasped during the conduct of the operation because of the risk of inadvertent air leaks caused by manual manipulation.