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Surgical treatment of pulmonary emphysema
BASIC SCIENCE SPECIAL FEATURE
bodies (near the bifurcation of the common carotid artery) and the aortic bodies scattered around the aortic arch. The carotid body afferents pass to the brainstem in the glossopharyngeal (IXth cranial) nerve. The aortic body afferents travel in the vagus (Xth cranial) nerve. Low PO2 rather than low CaO2 stimulates these receptors and ventilation is not increased in the resting anaemic subject. The carotid bodies are much more important than the aortic bodies and the ventilatory response to hypoxia is usually permanently lost if they are surgically removed. Their response to increased PaCO2 is faster (but less potent) than that of the central chemoreceptors. If a person is chronically exposed to a high or low PCO2, compensatory mechanisms return the pH of blood and cerebrospinal fluid to normal after a few days. This explains why a subject with severe chronic obstructive pulmonary disease can tolerate a PCO2 of 9 kPa (68 mmHg), which would cause extreme breathlessness if produced acutely in a normal subject. It also plays a part in the acclimatization to high altitude when the gradual return of the pH of cerebrospinal fluid to normal allows ventilation to rise after a few days, with some improvement in the arterial PO2.
• stretch receptors which can inhibit inspiration (the Hering–Breuer reflex) and possibly protect the lung from overdistension • juxtapulmonary capillary receptors which may be involved in the rapid shallow pattern of breathing that can occur in congested lungs. Receptors from muscles and joints, pain receptors, facial and laryngeal receptors can all have reflex affects on breathing. Breathing can also be affected by inputs from other CNS regions such as the cerebral cortex and defence areas of the hypothalamus. u
CROSS REFERENCE Ward J. Physiology of breathing I. Surgery 2005; 23(11): 419–23. FURTHER READING Hughes J M B, Pride N B. Lung function tests. London: W B Saunders, 1999. Lumb A B. Nunn’s applied respiratory physiology. 5th edition. Oxford: Butterworth-Heinemann, 2000. Ward J P T, Ward J, Wiener C M, Leach R M. The respiratory system at a glance. Oxford: Blackwell Publishing, 2002. West J B. Respiratory physiology—the essentials. 7th edition. Philadelphia: Lippincott Williams and Wilkins, 2004.
Other receptors that affect breathing: apart from chemoreceptors, many other receptors send afferents to the respiratory areas of the brainstem. In the lung, these include: • irritant receptors, which initiate coughing sneezing and/or bronchoconstriction
Classification: in pathological terms, emphysema is subdivided into three types. Centrilobular – commonly associated with smoking and inflammation of the distal airway. It involves the proximal acini and respiratory bronchioles, predominantly within the upper lobes. Panacinar – involves the entire acinus uniformly, is commonly associated with deficiency of α1-antitrypsin, and predominantly affects the lower lobes. Paraseptal – commonly associated with bullae formation and pneumothorax, it involves the distal acinus and is often subpleural.
Surgical treatment of pulmonary emphysema Paul Vaughan David A Waller
Chronic obstructive pulmonary disease is a major burden on healthcare in the ‘developed’ world. About 600,000 people in the UK have the disease; the prevalence is about 5% in men aged 65–75 years, increasing to 10% in men aged >75 years. Chronic obstructive pulmonary disease is strongly associated with cigarette smoking, although other noxious gases, particles and cannabis may be implicated.
Main features: destruction of the alveolar wall results in loss of alveolar surface area and loss of elastic recoil within the lung parenchyma. This reduction in compliance means less pressure is required to inflate the affected area and, once inflated, the loss of elastic tissue results in limitation of expiratory airflow. This eventually results in hyperinflation (increased total lung capacity) and air trapping (increased residual volume). The hyperinflation causes the classical features of emphysema: a flattened diaphragm, widened intercostal spaces, and increased work of breathing due to adverse mechanics of the chest wall. This unrewarded effort may be the reason for the sensation of dyspnoea. Bullous emphysema develops when an area of destruction of the alveolar wall reaches a size at which it fills preferentially to the adjacent normal lung. The elastic recoil of the surrounding lung retracts it away from the dilated airspace, thus enlarging the bulla. (A bulla is an enlarged airspace of >1 cm in diameter.) The outer surface is formed from the visceral pleura, whereas the
Pathophysiology Pulmonary emphysema is the abnormal dilation of air spaces distal to the terminal respiratory bronchiole (acinus) and is associated with destruction of the alveolar wall.
Paul Vaughan is a Clinical Research Fellow in Thoracic Surgery at Glenfield Hospital, Leicester, UK. David A Waller is a Consultant Thoracic Surgeon at Glenfield Hospital, Leicester, UK.
SURGERY 23:12
435
© 2005 The Medicine Publishing Company Ltd
BASIC SCIENCE
• •
inner layer consists of fibrous tissue formed from the destroyed adjacent lung. The inside of the bulla is crisscrossed by trabeculae of fibrotic interlobular and alveolar septae. Patients with emphysema experience a progressive decline in FEV1. Up to 40% of patients have increased pulmonary vascular resistance which may develop into secondary pulmonary hypertension (an increase in pulmonary artery pressure of 3–5 mmHg/year) and, ultimately, cor pulmonale. The abnormal pulmonary vascular resistance is thought to be due to a combination of hypoxic pulmonary vasoconstriction and pulmonary vascular remodelling, resulting in right ventricular dysfunction.
(V:Q) mismatch (see ‘Physiology of breathing II’, page 430). Surgery also has a part to play in the treatment of the commonest complication of emphysema—secondary spontaneous pneumothoraces. Surgery is not done for symptomatic improvement, but for treating the underlying defect, and creating pleural symphysis to prevent recurrence. Surgery may also be indicated if other complications (e.g. infected bulla, haemoptysis, carcinoma within the bulla (rare)) develop. Selection criteria: the main aim of patient selection is to: • identify those who remain significantly disabled despite maximal medical therapy • identify those with an acceptable surgical risk • exclude those predicted to have a poor outcome. Preoperative investigations consist of full pulmonary function testing (including body box plethysmography), analysis of arterial blood gases, an inspiratory posteroanterior erect radiograph of the chest, ECG, echocardiography, high-resolution CT of the chest and radionuclide perfusion scan to identify ‘functional target areas’ (Figure 1). Selection criteria for patients undergoing lung-volume reduction surgery have been developed over the last ten years (Figure 2).
Medical treatment There is no effective medical treatment to slow or reverse the decline in lung function associated with emphysema. Medical treatment involves smoking cessation, bronchodilator therapy (β2-agonists, anticholinergic bronchodilators, theophylline), corticosteroids, pulmonary rehabilitation and supplemental oxygen (if indicated).
Surgical treatment The aims of lung-volume reduction surgery and bullectomy are identical: symptomatic improvement. Bullectomy also treats the complications of chronic obstructive pulmonary disease (e.g. infected bulla, pneumothorax). The most severely affected areas are functionless in terms of gas exchange and occupy excess volume within the thorax; resection of these areas reduces the amount of functionless lung and also the degree of hyperinflation. Such procedures improve the mechanics of the chest wall and the range of diaphragmatic movement. The restoration of elastic recoil, and excision of non-functioning tissue improves the forced expiratory flow rate in one second (FEV1) and the ventilation:perfusion
Lung-volume reduction surgery was described by Brantigan (Maryland, USA) in 1956.1 Cooper (Missouri, USA) described a bilateral pneumectomy (Figure 3) via median sternotomy, which resulted in significant improvements in FEV1, total lung capacity, residual volume, six-minute walk test, dyspnoea, oxygen requirement and quality of life.2 Results differed between centres, causing doubts over its effectiveness, and led to a randomized controlled clinical trial of lung-volume reduction surgery—the National Emphysema Treatment Trial, published in 2003.3 National Emphysema Treatment Trial – 1200 patients with severe emphysema underwent pulmonary rehabilitation and were
a Anterior view.
b Posterior view.
Quantitative radionuclide perfusion scintigraphy showing a anterior and b posterior views of the lung. The ‘target area’ is in the right upper zone. 1
SURGERY 23:12
436
© 2005 The Medicine Publishing Company Ltd
BASIC SCIENCE
Indications and contraindications for lung volume reduction surgery Indications Pulmonary function tests FEV1 20–40% RV >120%, TLC >120% DLCO >25%, pCO2 <7kPa Symptoms Dyspnoea MRC 3–5 ‘Target areas’ Anatomical Functional
General Smoking cessation Compliance with pulmonary rehabilitation programme Objective exercise test
Obstruction Distension Destruction
High-resolution CT Radionuclide perfusion scintigraphy
6-minute walk test or shuttle walk test
Fitness for surgery Nutritional state
Contraindications Radiographic Homogeneous emphysema/no target areas on high-resolution CT and perfusion scintigraphy Pulmonary Giant bulla Pulmonary nodule of unknown histology Pulmonary hypertension Recurrent infections of the lower respiratory tract Bronchiectasis Hypercapnia (pCO2 >7 kPa) KCO <25% predicted Ventilator dependent Cardiovascular Recent myocardial infarction (within 6 weeks) Impaired left or right ventricular function Significant arrhythmia Others Disease reducing life expectancy Previous chest surgery
FEV1: Forced expiratory volume in one second; RV: Residual volume; TLC: Total lung capacity; DLCO: Carbon monoxide diffusion in the lung; pCO2: Partial pressure of carbon dioxide; MRC: Maximum recycling capacity; KCO: Transfer coefficient. 2
randomized to receive continued best medical treatment or undergo lung-volume reduction surgery. Overall, lung-volume reduction surgery offered no survival benefit when compared to medical therapy—even when a subgroup of ‘high risk’ surgical patients was excluded from the comparison. Patients who received surgery were more likely to show improvements in exercise capacity and quality of life. Through a secondary analysis of the data, two factors were identified as having potential value in predicting benefit from lung-volume reduction surgery: distribution of the emphysema in the upper lobe, and low exercise capacity. The two risk factors are additive, thus surgery in a patient with both factors may even reduce mortality. Conversely, patients without disease of the upper lobe and a preserved exercise capacity had a higher risk of death with surgery and no evidence of a reduction in morbidity. Procedure – lung-volume reduction surgery may be done by open or video-assisted thoracic surgery; on both lungs at the same operation or in two stages; the best surgical approach has not been determined. Lung-volume reduction surgery is done on the previously identified target areas and entails a stapled resection of peripheral lung tissue (Figure 4). The staple lines may be buttressed using bovine pericardial strips. Prolonged leaks of air are the commonest source of morbidity; mortality rates are relatively low (3–8%).3, 4 Early mobilization and good analgesia are critically important in the postoperative period. A thoracic epidural catheter is placed peroperatively to facilitate intra- and postoperative analgesia, while one-way flutter-valve drainage systems enable early mobilization. Outcome is assessed by spirometry and health (and even nutritional) status. The FEV1 improves by about 50% after a bilateral
Lung-volume reduction surgery
Non-anatomical resection of 30–50% of peripheral lung tissue in the affected lobe, excised from the apex of the upper lobe. Black arrows indicate the pericardial buttressed staple line. The dotted line indicates the extent of resection from the right upper lobe.
3
SURGERY 23:12
437
© 2005 The Medicine Publishing Company Ltd
BASIC SCIENCE
4 Resected specimen from a patient undergoing lung-volume reduction surgery. Black arrows indicate the free edge of the right upper lobe. White arrows indicate the bovine pericardial buttressed linear staples.
5 CT reconstruction shows a single ‘giant’ bulla (arrows) affecting the left upper lobe in a 50-year-old male smoker.
procedure and 30% after a unilateral procedure. The latter has the advantages of being less invasive (particularly if done by videoassisted thoracic surgery), a smoother postoperative recovery, with a slower rate of decline in FEV1 postoperatively. Further surgery on the contralateral lung can be done if symptoms deteriorate, but the timing of such surgery has not been determined. Body mass index is significantly increased for up to three years after lung-volume reduction surgery and has been correlated with the increase in FEV1.
Endobronchial therapy: recent research has been directed towards bronchoscopic lung-volume reduction surgery because of the morbidity and mortality associated with surgery. In this procedure, one-way valves that obstruct segmental bronchi are placed permanently in the airway. Valves can be removed using graspers through the working channel of the bronchoscope. The lung tissue distal to the valve collapses due to resorption of the air into the pulmonary circulation, reducing the hyperinflation associated with emphysema. Emphysema is a non-anatomical destruction of peripheral airways, thus in some cases functioning lung may be lost by segmental collapse. The future of this less invasive procedure remains to be determined by long-term follow-up studies. Airway bypass is another promising concept. This endoscopic procedure is based upon the concept of ‘collateral ventilation’ (i.e. the ability of gas to move from one part of the lung to another through non-anatomical pathways). Artificial communications are created using a radiofrequency catheter and stent between emphysematous lung parenchyma and a segmental bronchus, facilitating deflation of the obstructed hyperinflated segment. Improvements in FEV1 have been shown, but short-term results from one clinical trial are controversial. u
Bullectomy: after complete mobilization of the lung, video-assisted thoracoscopic bullectomy is facilitated by controlled deflation of the affected area, followed by stapling of the controlled puncture site. Excision of the deflated bulla is done with a rim of normal lung tissue. Patient selection is one of the most important aspects of successful surgery for bullous emphysema. Patients who will benefit the most from bullectomy can be predicted using the deVries–Wolfe classification of bullous disease. Those patients with stage I or II (single or multiple ‘giant’ bullae with relatively normal underlying lung tissue) disease are ideal candidates for surgery and have the best improvement in function. Patients with stage III (homogeneous bullous) disease must be carefully evaluated and selected because the functional outcomes are less predictable. Elective bullectomy improves symptoms and respiratory function in patients with moderate-to-severe dyspnoea and bullae occupying more than one-third of the hemithorax (Figure 5).
REFERENCES 1 Brantigan O C, Mueller E, Kress M B. A surgical approach to pulmonary emphysema. Am Rev Respir Dis 1956; 80: 194–206. 2 Cooper J D, Trulock E P, Triantafillou A N et al. Bilateral pneumectomy (volume reduction) for chronic obstructive pulmonary disease. J Thorac Cardiovasc Surg 1995; 109: 106–16. 3 National Emphysema Treatment Trial Research Group. A randomized trial comparing lung-volume-reduction surgery with medical therapy for severe emphysema. New Engl J Med 2003; 348: 2059–73. 4 Oey I F, Waller D A, Bal S et al. Lung volume reduction surgery—a comparison of the long term outcome of unilateral vs bilateral approaches. Eur J Cardiothorac Surg 2002; 22: 610–14. 5 Henry M, Arnold T, Harvey J; Pleural Diseases Group, Standards of Care Committee, British Thoracic Society. BTS guidelines for the management of spontaneous pneumothorax. Thorax 2003; 58(Suppl 2): 39–52.
Spontaneous pneumothorax: secondary spontaneous pneumothorax is thought to represent a significant marker of mortality. The surgical principles are outlined above (closure of the defect causing the air leak, and the creation of pleural symphysis by parietal pleurectomy or talc insufflation). Treatment using video-assisted thoracic surgery is established, but controversy exists regarding the optimum timing of surgical intervention, surgical approach, and the ideal method of pleurodesis. The latest guidelines from the British Thoracic Society advise referral to a thoracic surgeon after 3–5 days in cases of persistent air leak or failure of the lung to re-expand despite adequate intercostal drainage.5
SURGERY 23:12
438
© 2005 The Medicine Publishing Company Ltd
bodies (near the bifurcation of the common carotid artery) and the aortic bodies scattered around the aortic arch. The carotid body afferents pass to the brainstem in the glossopharyngeal (IXth cranial) nerve. The aortic body afferents travel in the vagus (Xth cranial) nerve. Low PO2 rather than low CaO2 stimulates these receptors and ventilation is not increased in the resting anaemic subject. The carotid bodies are much more important than the aortic bodies and the ventilatory response to hypoxia is usually permanently lost if they are surgically removed. Their response to increased PaCO2 is faster (but less potent) than that of the central chemoreceptors. If a person is chronically exposed to a high or low PCO2, compensatory mechanisms return the pH of blood and cerebrospinal fluid to normal after a few days. This explains why a subject with severe chronic obstructive pulmonary disease can tolerate a PCO2 of 9 kPa (68 mmHg), which would cause extreme breathlessness if produced acutely in a normal subject. It also plays a part in the acclimatization to high altitude when the gradual return of the pH of cerebrospinal fluid to normal allows ventilation to rise after a few days, with some improvement in the arterial PO2.
• stretch receptors which can inhibit inspiration (the Hering–Breuer reflex) and possibly protect the lung from overdistension • juxtapulmonary capillary receptors which may be involved in the rapid shallow pattern of breathing that can occur in congested lungs. Receptors from muscles and joints, pain receptors, facial and laryngeal receptors can all have reflex affects on breathing. Breathing can also be affected by inputs from other CNS regions such as the cerebral cortex and defence areas of the hypothalamus. u
CROSS REFERENCE Ward J. Physiology of breathing I. Surgery 2005; 23(11): 419–23. FURTHER READING Hughes J M B, Pride N B. Lung function tests. London: W B Saunders, 1999. Lumb A B. Nunn’s applied respiratory physiology. 5th edition. Oxford: Butterworth-Heinemann, 2000. Ward J P T, Ward J, Wiener C M, Leach R M. The respiratory system at a glance. Oxford: Blackwell Publishing, 2002. West J B. Respiratory physiology—the essentials. 7th edition. Philadelphia: Lippincott Williams and Wilkins, 2004.
Other receptors that affect breathing: apart from chemoreceptors, many other receptors send afferents to the respiratory areas of the brainstem. In the lung, these include: • irritant receptors, which initiate coughing sneezing and/or bronchoconstriction
Classification: in pathological terms, emphysema is subdivided into three types. Centrilobular – commonly associated with smoking and inflammation of the distal airway. It involves the proximal acini and respiratory bronchioles, predominantly within the upper lobes. Panacinar – involves the entire acinus uniformly, is commonly associated with deficiency of α1-antitrypsin, and predominantly affects the lower lobes. Paraseptal – commonly associated with bullae formation and pneumothorax, it involves the distal acinus and is often subpleural.
Surgical treatment of pulmonary emphysema Paul Vaughan David A Waller
Chronic obstructive pulmonary disease is a major burden on healthcare in the ‘developed’ world. About 600,000 people in the UK have the disease; the prevalence is about 5% in men aged 65–75 years, increasing to 10% in men aged >75 years. Chronic obstructive pulmonary disease is strongly associated with cigarette smoking, although other noxious gases, particles and cannabis may be implicated.
Main features: destruction of the alveolar wall results in loss of alveolar surface area and loss of elastic recoil within the lung parenchyma. This reduction in compliance means less pressure is required to inflate the affected area and, once inflated, the loss of elastic tissue results in limitation of expiratory airflow. This eventually results in hyperinflation (increased total lung capacity) and air trapping (increased residual volume). The hyperinflation causes the classical features of emphysema: a flattened diaphragm, widened intercostal spaces, and increased work of breathing due to adverse mechanics of the chest wall. This unrewarded effort may be the reason for the sensation of dyspnoea. Bullous emphysema develops when an area of destruction of the alveolar wall reaches a size at which it fills preferentially to the adjacent normal lung. The elastic recoil of the surrounding lung retracts it away from the dilated airspace, thus enlarging the bulla. (A bulla is an enlarged airspace of >1 cm in diameter.) The outer surface is formed from the visceral pleura, whereas the
Pathophysiology Pulmonary emphysema is the abnormal dilation of air spaces distal to the terminal respiratory bronchiole (acinus) and is associated with destruction of the alveolar wall.
Paul Vaughan is a Clinical Research Fellow in Thoracic Surgery at Glenfield Hospital, Leicester, UK. David A Waller is a Consultant Thoracic Surgeon at Glenfield Hospital, Leicester, UK.
SURGERY 23:12
435
© 2005 The Medicine Publishing Company Ltd
BASIC SCIENCE
• •
inner layer consists of fibrous tissue formed from the destroyed adjacent lung. The inside of the bulla is crisscrossed by trabeculae of fibrotic interlobular and alveolar septae. Patients with emphysema experience a progressive decline in FEV1. Up to 40% of patients have increased pulmonary vascular resistance which may develop into secondary pulmonary hypertension (an increase in pulmonary artery pressure of 3–5 mmHg/year) and, ultimately, cor pulmonale. The abnormal pulmonary vascular resistance is thought to be due to a combination of hypoxic pulmonary vasoconstriction and pulmonary vascular remodelling, resulting in right ventricular dysfunction.
(V:Q) mismatch (see ‘Physiology of breathing II’, page 430). Surgery also has a part to play in the treatment of the commonest complication of emphysema—secondary spontaneous pneumothoraces. Surgery is not done for symptomatic improvement, but for treating the underlying defect, and creating pleural symphysis to prevent recurrence. Surgery may also be indicated if other complications (e.g. infected bulla, haemoptysis, carcinoma within the bulla (rare)) develop. Selection criteria: the main aim of patient selection is to: • identify those who remain significantly disabled despite maximal medical therapy • identify those with an acceptable surgical risk • exclude those predicted to have a poor outcome. Preoperative investigations consist of full pulmonary function testing (including body box plethysmography), analysis of arterial blood gases, an inspiratory posteroanterior erect radiograph of the chest, ECG, echocardiography, high-resolution CT of the chest and radionuclide perfusion scan to identify ‘functional target areas’ (Figure 1). Selection criteria for patients undergoing lung-volume reduction surgery have been developed over the last ten years (Figure 2).
Medical treatment There is no effective medical treatment to slow or reverse the decline in lung function associated with emphysema. Medical treatment involves smoking cessation, bronchodilator therapy (β2-agonists, anticholinergic bronchodilators, theophylline), corticosteroids, pulmonary rehabilitation and supplemental oxygen (if indicated).
Surgical treatment The aims of lung-volume reduction surgery and bullectomy are identical: symptomatic improvement. Bullectomy also treats the complications of chronic obstructive pulmonary disease (e.g. infected bulla, pneumothorax). The most severely affected areas are functionless in terms of gas exchange and occupy excess volume within the thorax; resection of these areas reduces the amount of functionless lung and also the degree of hyperinflation. Such procedures improve the mechanics of the chest wall and the range of diaphragmatic movement. The restoration of elastic recoil, and excision of non-functioning tissue improves the forced expiratory flow rate in one second (FEV1) and the ventilation:perfusion
Lung-volume reduction surgery was described by Brantigan (Maryland, USA) in 1956.1 Cooper (Missouri, USA) described a bilateral pneumectomy (Figure 3) via median sternotomy, which resulted in significant improvements in FEV1, total lung capacity, residual volume, six-minute walk test, dyspnoea, oxygen requirement and quality of life.2 Results differed between centres, causing doubts over its effectiveness, and led to a randomized controlled clinical trial of lung-volume reduction surgery—the National Emphysema Treatment Trial, published in 2003.3 National Emphysema Treatment Trial – 1200 patients with severe emphysema underwent pulmonary rehabilitation and were
a Anterior view.
b Posterior view.
Quantitative radionuclide perfusion scintigraphy showing a anterior and b posterior views of the lung. The ‘target area’ is in the right upper zone. 1
SURGERY 23:12
436
© 2005 The Medicine Publishing Company Ltd
BASIC SCIENCE
Indications and contraindications for lung volume reduction surgery Indications Pulmonary function tests FEV1 20–40% RV >120%, TLC >120% DLCO >25%, pCO2 <7kPa Symptoms Dyspnoea MRC 3–5 ‘Target areas’ Anatomical Functional
General Smoking cessation Compliance with pulmonary rehabilitation programme Objective exercise test
Obstruction Distension Destruction
High-resolution CT Radionuclide perfusion scintigraphy
6-minute walk test or shuttle walk test
Fitness for surgery Nutritional state
Contraindications Radiographic Homogeneous emphysema/no target areas on high-resolution CT and perfusion scintigraphy Pulmonary Giant bulla Pulmonary nodule of unknown histology Pulmonary hypertension Recurrent infections of the lower respiratory tract Bronchiectasis Hypercapnia (pCO2 >7 kPa) KCO <25% predicted Ventilator dependent Cardiovascular Recent myocardial infarction (within 6 weeks) Impaired left or right ventricular function Significant arrhythmia Others Disease reducing life expectancy Previous chest surgery
FEV1: Forced expiratory volume in one second; RV: Residual volume; TLC: Total lung capacity; DLCO: Carbon monoxide diffusion in the lung; pCO2: Partial pressure of carbon dioxide; MRC: Maximum recycling capacity; KCO: Transfer coefficient. 2
randomized to receive continued best medical treatment or undergo lung-volume reduction surgery. Overall, lung-volume reduction surgery offered no survival benefit when compared to medical therapy—even when a subgroup of ‘high risk’ surgical patients was excluded from the comparison. Patients who received surgery were more likely to show improvements in exercise capacity and quality of life. Through a secondary analysis of the data, two factors were identified as having potential value in predicting benefit from lung-volume reduction surgery: distribution of the emphysema in the upper lobe, and low exercise capacity. The two risk factors are additive, thus surgery in a patient with both factors may even reduce mortality. Conversely, patients without disease of the upper lobe and a preserved exercise capacity had a higher risk of death with surgery and no evidence of a reduction in morbidity. Procedure – lung-volume reduction surgery may be done by open or video-assisted thoracic surgery; on both lungs at the same operation or in two stages; the best surgical approach has not been determined. Lung-volume reduction surgery is done on the previously identified target areas and entails a stapled resection of peripheral lung tissue (Figure 4). The staple lines may be buttressed using bovine pericardial strips. Prolonged leaks of air are the commonest source of morbidity; mortality rates are relatively low (3–8%).3, 4 Early mobilization and good analgesia are critically important in the postoperative period. A thoracic epidural catheter is placed peroperatively to facilitate intra- and postoperative analgesia, while one-way flutter-valve drainage systems enable early mobilization. Outcome is assessed by spirometry and health (and even nutritional) status. The FEV1 improves by about 50% after a bilateral
Lung-volume reduction surgery
Non-anatomical resection of 30–50% of peripheral lung tissue in the affected lobe, excised from the apex of the upper lobe. Black arrows indicate the pericardial buttressed staple line. The dotted line indicates the extent of resection from the right upper lobe.
3
SURGERY 23:12
437
© 2005 The Medicine Publishing Company Ltd
BASIC SCIENCE
4 Resected specimen from a patient undergoing lung-volume reduction surgery. Black arrows indicate the free edge of the right upper lobe. White arrows indicate the bovine pericardial buttressed linear staples.
5 CT reconstruction shows a single ‘giant’ bulla (arrows) affecting the left upper lobe in a 50-year-old male smoker.
procedure and 30% after a unilateral procedure. The latter has the advantages of being less invasive (particularly if done by videoassisted thoracic surgery), a smoother postoperative recovery, with a slower rate of decline in FEV1 postoperatively. Further surgery on the contralateral lung can be done if symptoms deteriorate, but the timing of such surgery has not been determined. Body mass index is significantly increased for up to three years after lung-volume reduction surgery and has been correlated with the increase in FEV1.
Endobronchial therapy: recent research has been directed towards bronchoscopic lung-volume reduction surgery because of the morbidity and mortality associated with surgery. In this procedure, one-way valves that obstruct segmental bronchi are placed permanently in the airway. Valves can be removed using graspers through the working channel of the bronchoscope. The lung tissue distal to the valve collapses due to resorption of the air into the pulmonary circulation, reducing the hyperinflation associated with emphysema. Emphysema is a non-anatomical destruction of peripheral airways, thus in some cases functioning lung may be lost by segmental collapse. The future of this less invasive procedure remains to be determined by long-term follow-up studies. Airway bypass is another promising concept. This endoscopic procedure is based upon the concept of ‘collateral ventilation’ (i.e. the ability of gas to move from one part of the lung to another through non-anatomical pathways). Artificial communications are created using a radiofrequency catheter and stent between emphysematous lung parenchyma and a segmental bronchus, facilitating deflation of the obstructed hyperinflated segment. Improvements in FEV1 have been shown, but short-term results from one clinical trial are controversial. u
Bullectomy: after complete mobilization of the lung, video-assisted thoracoscopic bullectomy is facilitated by controlled deflation of the affected area, followed by stapling of the controlled puncture site. Excision of the deflated bulla is done with a rim of normal lung tissue. Patient selection is one of the most important aspects of successful surgery for bullous emphysema. Patients who will benefit the most from bullectomy can be predicted using the deVries–Wolfe classification of bullous disease. Those patients with stage I or II (single or multiple ‘giant’ bullae with relatively normal underlying lung tissue) disease are ideal candidates for surgery and have the best improvement in function. Patients with stage III (homogeneous bullous) disease must be carefully evaluated and selected because the functional outcomes are less predictable. Elective bullectomy improves symptoms and respiratory function in patients with moderate-to-severe dyspnoea and bullae occupying more than one-third of the hemithorax (Figure 5).
REFERENCES 1 Brantigan O C, Mueller E, Kress M B. A surgical approach to pulmonary emphysema. Am Rev Respir Dis 1956; 80: 194–206. 2 Cooper J D, Trulock E P, Triantafillou A N et al. Bilateral pneumectomy (volume reduction) for chronic obstructive pulmonary disease. J Thorac Cardiovasc Surg 1995; 109: 106–16. 3 National Emphysema Treatment Trial Research Group. A randomized trial comparing lung-volume-reduction surgery with medical therapy for severe emphysema. New Engl J Med 2003; 348: 2059–73. 4 Oey I F, Waller D A, Bal S et al. Lung volume reduction surgery—a comparison of the long term outcome of unilateral vs bilateral approaches. Eur J Cardiothorac Surg 2002; 22: 610–14. 5 Henry M, Arnold T, Harvey J; Pleural Diseases Group, Standards of Care Committee, British Thoracic Society. BTS guidelines for the management of spontaneous pneumothorax. Thorax 2003; 58(Suppl 2): 39–52.
Spontaneous pneumothorax: secondary spontaneous pneumothorax is thought to represent a significant marker of mortality. The surgical principles are outlined above (closure of the defect causing the air leak, and the creation of pleural symphysis by parietal pleurectomy or talc insufflation). Treatment using video-assisted thoracic surgery is established, but controversy exists regarding the optimum timing of surgical intervention, surgical approach, and the ideal method of pleurodesis. The latest guidelines from the British Thoracic Society advise referral to a thoracic surgeon after 3–5 days in cases of persistent air leak or failure of the lung to re-expand despite adequate intercostal drainage.5
SURGERY 23:12
438
© 2005 The Medicine Publishing Company Ltd