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 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 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 lung 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

Operative procedures for bleb resection are primarily indicated secondary to 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 4–7 days warrants consideration of operative intervention. Pneumothorax recurs at a rate of 20–30% 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.

While patients with bulla (single or multiple) may present with pneumothorax or dyspnea, patients with giant bullectomy 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.

A bullous lesion can be approached via minithoracotomy or, preferably, 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 thorascopic 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

Preoperative assessment of patients presenting with bleb disease and spontaneous pneumothorax may be limited. If the patient is a nonsmoker, less than 30 years, and without history of carcinoma, sarcoma, or immunodeficiency, a chest x-ray with evidence of normal lung parenchyma should suffice. However, if the patient is older or has 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. Patients who are immunocompromised (e.g., by immunosupression 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.

For the surgery to be successful, 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, 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 (D_LCO) is a predictable reflection of the viability of nonbullous lung tissue, and patients with preserved D_LCO 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.

TECHNIQUE

Anesthesia

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.

Surgical Management

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 thorascopic 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.

SURGICAL TECHNIQUES FOR SPONTANEOUS PNEUMOTHORAX

Bleb Resection

Figure 86-1 illustrates possible port placement for patients presenting with spontaneous pneumothorax. Note that the "operative triangle" is placed in the anterior axillary region; the largest stapling port is placed in the anterior position. Exploration is begun with a 5-mm 30-degree scope. The posterior axillary port may either be a 5-mm port or an incision to place a curved sponge stick. This access port is used to manipulate the lung for exploration. Examination of the entire lung parenchyma is undertaken with explicit attention to the apical segment of the upper lobe and the superior segment of the lower lobe. Identified blebs are stapled using a 35-mm device with 3.5-mm "blue" stapler loads and with resection of minimal lung tissue.

In a multi-institutional study reported by Naunheim and colleagues,¹⁰ blebs were identified in more than one lobe in 10% of the patients, and in 9% of patients, no bleb could be identified. When no discrete bleb is identified, great care should be taken to look for areas of scarring or visceral pleural changes on the lung that could represent changes from a decompressed bleb. Even if no abnormalities are found, apical stapling of the upper lobe still should be performed. Specimens are removed from the chest either in a protected bag or within the confines of the largest port. Pleural abrasion then should be performed; my preference is mechanical abrasion with the aid of a folded Bovie scratch pad or endoscopic peanut device. Talc insufflation should be avoided because the long-term effects are not well defined, and the severe granulomatous reaction may impede future possible thoracic interventions. Pleurectomy usually is not necessary and may add to the risk of bleeding or complicate future chest interventions. A single no. 24 chest tube is placed into the most inferior (5-mm) port; thoracoscopic visualization of the tube placement is always performed. To minimize barotrauma to the dependent lung, the contralateral "down" lung is clamped during reexpansion of the operative lung. Active expansion of the lung during ventilation is observed. The chest tube is placed on suction and kept on suction during postoperative day 1 to help promote pleural symphysis. The tube may be removed and the patient discharged on postoperative day 2, provided that there are no persistent air leaks.

Resection of Bullous and Giant Bullous Disease

After initial placement of the double-lumen tube, single-lung ventilation should commence as soon a possible to avoid further hyperinflation of the bullous disease on the operative side and to facilitate decompression of the bulla. Figure 86-2 illustrates operative port placement for giant bullous disease (Fig. 86-3). Note that the "operative triangle" is shifted more caudad but still maintains an anterior orientation. If the bullous lesion is based in an inferior portion of the chest, the triangle may be shifted even lower. Again, a 5-mm 30-degree scope is placed to explore the chest initially. Relatively normal or spared lung should become atelectatic at a faster rate than lung tissue with bullous disease, exaggerating the demarcation between the most diseased and the relatively normal lung parenchyma. The operative course is enhanced by early decompression of the giant bulla or bullous area using a long Bovie-tip electrocautery (Fig. 86-4). The now deflated bulla is grasped at its apex, and the demarcation between bullous and nonbullous disease is delineated with either a sponge stick or thorascopic Landreneau masher (Pilling Surgical, Teleflex, Inc., Research Triangle Park, NC) (Fig. 86-5). The base of the bulla then is plicated using a 45-mm-long linear stapler with buttressed support (Fig. 86-6). Great care is taken to plicate the bulla completely to avoid any residuum while retaining as much normal tissue as possible. The resected bulla then is placed in an endoscopic bag and removed from the chest in a protected fashion. It is important to remove the tissue in this manner to avoid seeding the chest or chest wall in the case of occult carcinoma or infection. Pleural management with abrasion then should be performed. In patients with limited lung reexpansion, consideration may be given to the development of an apical pleural tent. Two no. 24 chest tubes are left in place; preferentially, these should be placed on water seal.

POSTOPERATIVE MANAGEMENT

Postoperative management is straightforward for primary bleb resection for pneumothorax. In these patients, the chest tube is left on suction during postoperative day 1 to promote pleural symphysis. The tube may be removed on postoperative day 2 if no leak is apparent, and the patient can be discharged to home. The patient is instructed to limit activities that significantly increase intrathoracic pressure for 4 weeks.

The postoperative care of patients with bullous or giant bullous disease may be more challenging depending on the extent of the underlying emphysema. The operative and anesthetic plan should provide for extubation in the OR. Postoperative hypercarbia should be tolerated unless it is accompanied by systemic acidosis. Oxygen supplementation should be used only as needed to keep saturations above 90%. Excellent pain control, preferably with an epidural, is essential to avoid splinting, atelectasis, and retained secretions. IV nonsteroidal anti-inflammatory medication may enhance pain control significantly. The patient should be mobilized out of bed as early as possible starting on the day of surgery, and physical therapy should begin on postoperative day 1. The chest tubes are preferentially placed on water seal as long as there is pleural apposition on chest x-ray. For patients with extensive air leaks, early placement of the chest tube to Heimlich valve may facilitate resolution of the leak. Patients with persistent leak with Heimlich valve in place may be discharged to home and assessed on a weekly basis.

COMPLICATIONS

Prolonged air leak is the primary morbidity of patients undergoing significant bullectomy and occurs in 30–50% of patients. Intraoperative techniques, including the use of buttressed sutures and strict adherence to a no-touch technique with respect to all lung tissue that is not intended for resection, may help to decrease the severity and duration of air leaks. Early placement to water seal and Heimlich valve will facilitate earlier resolution of air leaks. Frequently, significant air leaks are accompanied by subcutaneous emphysema. Subcutaneous emphysema is a benign process predominantly, but it can be palliated by placing the chest tubes to suction. In severe cases, subcutaneous emphysema also may be palliated by venting/incising the skin and decompressing the patient. With time, air leaks virtually always resolve, and one should be able to avoid reoperation.

Respiratory failure may occur postoperatively and primarily reflects high-risk patients with lower FEV₁ and/or low D_LCO values. Patients with a bronchial component to their symptoms may require frequent postoperative bronchoscopy and may have a higher incidence of respiratory complications. Pneumonia is often encountered during an extended hospital course and should be treated aggressively. Other common complications include atrial fibrillation and bowel complications. Gastrointestinal complications may include Ogilvie's type colonic distention, ischemic colitis, and Clostridium difficile colitis. Aggressive early intervention and attention to these issues may reduce potential morbidity and mortality significantly. Adequate pain control is an essential component of the patient's postoperative pulmonary function and airway clearance. Even with thoracoscopy, a well-functioning epidural is essential.

Uncommon complications may include bleeding, reexpansion pulmonary edema,¹¹ and even chronic pain. These complications may be avoided with careful surgical technique and gentle reexpansion of the lung. Most chronic pain can be avoided by placing the ports in anterior portions of the chest to take advantage of wider interspaces and by placing torque on the intercostal vessels and nerves.

RESULTS

The results of treatment of spontaneous pneumothorax are well documented. Present-day techniques with video-assisted thoracic surgery should be considered the standard of care. Naunhiem and colleagues have reported their early results using video-assisted thoracic surgery (VATS).¹⁰ Of 113 patients, there were no deaths, no episodes of postoperative bleeding, and the incidence of recurrent pneumothorax was only 4.1%. The only predictor for recurrence was failure to identify and ablate a bleb at operation, resulting in a 23% recurrence rate versus 1.8% when the bleb was identified properly and ablated. A larger and more recent publication by Liu and colleagues reported 757 patients treated by VATS for spontaneous pneumothorax.¹² In 49 patients of this series, no blebs or bullae were identified. A recurrence rate of 2.1% was reported for the entire cohort. Increased recurrence was documented in patients with no blebs identified at initial operation and, to a lesser extent, for patients with multiple blebs.

The group at Barnes-Jewish Hospital in St. Louis, Missouri, has reported outcomes after resection of giant emphysematous bulla.¹³ Forty-three patients with giant emphysematous bullae were reported, with a mean patient follow-up of 4.5 years. Reflecting the severity of the underlying lung disease in these patients, 79% had nonfatal complications, consisting predominantly of air leak. One patient died (4.3%). Physiologic results included an increase in FEV₁ from 32% at baseline to 55% at 1 year and 49% at 3 years. D_LCO and distance walked in 6 minutes increased significantly at 6 months and 3 years. Continuous use of oxygen decreased from 42% at baseline to 7% at 6 months and 21% at 3 years. Dyspnea score also was reported, with 86% reporting relief of dyspnea at 1 year and 81% at 3 years. Similar increases in pulmonary function values using minimally invasive techniques have been documented by Divisi and colleagues.⁴

EDITOR'S COMMENT

The localized deformation of lung parenchyma can be very similar in both normal and emphysematous patients. In addition to reducing the risk of pneumothorax, resecting bullous disease removes nonfunctioning lung tissue and allows the expansion of more functional regions of the lung. This principle can be similarly applied to lung volume reduction surgery.

–SJM

REFERENCES