ANATOMY OF THE PLEURA

ANATOMY OF THE PLEURA The pleura develops in the embryo from the coelomic cavity (fetal body cavity). The coelomic cavity is where the vital organs (heart, bowels, and lungs) will develop. This cavity will then be divided into the peritoneal cavity and the pleural space by the septum transversum and the pleuroperitoneal membranes. The pleural space will later be separated into two distinct cavities by the pericardium. The lungs then develop from the premordial buds (central mass of mesenchyme) and as they grow laterally, they invaginate each pleural space, thus taking its pleural covering. The pleura covers the entire thoracic cavity (parietal pleura) and the lungs (visceral pleura). The pleural layers are reflected back-to-back in the interlobar fissures, and at the pulmonary ligament which extends from the hilum down to the diaphragm. The pleural space is a potential space that contains minute amounts of pleural fluid essential for lubricating expansion and movement of the lungs. The lung fills the pleural space during deep inspiration, while during expiration, the lung retracts and the costal parietal pleura and the diaphragmatic pleura may come in apposition and for the pleural recesses. The pleura is composed of five layers: (1) a single layer of mesothelial cells, (2) a thin submesothelial connective tissue layer, (3) a thin superficial elastic layer, (4) a loose connective tissue layer, and (5) a deep fibroelastic layer. The surface of the mesothelial cells contains microvilli. These microvilli were thought to function in the absorption of fluid, but recently, it has been shown to enmesh glycoproteins to lubricate the gliding of both pleural layers. The parietal pleura receives its blood supply from systemic capillaries. Small branches of the intercostal arteries supply the costal pleura, whereas the mediastinal pleura is principally by the pericardiophrenic artery. The diaphragmatic pleura is supplied by the superior phrenic and musculophrenic arteries. The blood supply of the visceral pleura in humans and animals with thick pleura originates from the systemic circulation via the bronchial arteries. Investigators have demonstrated that in sheep -an animal with thick pleura- the visceral pleura is supplied completely and exclusively by the bronchial artery. Since humans have thick pleura, it is possible that the visceral pleura is suppplied similarly, although there is still controversy concerning this. The venous drainage of the parietal pleura is through the intercostal veins (systemic veins) while the visceral pleura drains to pulmonary veins. The lymphatics of the parietal pleura drain the pleural fluid and any noxious particles that reach the pleura. The lymphatic system starts with small stomas that communicate to lymphatic foci that will drain through lymphatic vessels to nodes along the internal thoracic artery and to the internal intercostal nodes (along the heads of the ribs posteriorly). The parietal pleural lymphatics can remove about 20 times the fluid formed under normal conditions (up to 0.2 mL per kg per hour). The visceral pleura drains through two systems: a) a superficial system that floats over the surface of the lung towards the hilum, and b) a deep system that penetrates the lung parenchyma to reach the hilar nodes. Sensory nerves endings are present in the costal and diaphragmatic parietal pleura. The intercostal nerves supply the costal pleura and the peripheral part of the diaphragmatic pleura. When either of these areas is stimulated, pain is referred to the adjacent chest wall. In contrast, the central portion of the diaphragmatic pleura is innervated by the phrenic nerve, and stimulation of this part of the pleura causes pain that is referred to the ipsilateral shoulder. The visceral pleura contains no pain fibers Physiology of The Pleural Space 1) Pleural pressure: The pleural pressure is subatmospheric due to the tendency of the lung to collapse versus the tendency of the chest wall to expand. This negative pleural pressure keeps the inflated. There exists a pressure gradient between the superior and the inferior portions of the pleura, with the superior portions being lowest (more negative). The magnitude of the pressure gradient appears to be approximately 0.5 cm H 2O per cm vertical distance. Considering the size of the lung to be 25 cm in height in normal persons, the difference in pleural pressure between the apex and the base may be around 12 cm H 2O. 2) Pleural Fluid Formation: Pleural fluid is normally formed from parietal pleural capillaries. The forces governing this process are the pleural capillaries hydrostatic pressure and the oncotic pressure of the pleural capillaries and the oncotic pressure of fluid in the pleura space. This can be summarized in the following schematic illustration. PARIETAL PLEURA P L E U R A L S P A C E Hydrostatic pressure -5 35 6 29 0 VISCERAL PLEURA 30 +24 29 34 5 Oncotic pressure 29 34 This illustration shows that the pleural fluid is normally formed from filtration from the parietal pleural capillaries with a gradient of ~6 cm H 2O. It is noteworthy to remember that the fluid is also removed from the pleural space through the parietal pleural lymphatics through the lymphatic stomas. Normally, 0.01 mL per Kg per hour is formed through pleural fluid lymphatics. 2) Other Origins of Pleural Fluid: a) Interstitial origin: in conditions where the interstitial tissues of the lung are overloaded with transudate (e.g., high pressure or high permeability pulmonary edema), fluid may escape in the pleural space. The fluid is then removed through parietal pleural lymphatics which have the ability to remove considerable amounts of fluid. b) Peritoneal cavity: ascetic fluid can pass to the pleural space through minute openings in the diaphragm. This can be seen in cases of hepatic hydrothorax, Meig‟s syndrome, and peritoneal dialysis. c) Thoracic duct or blood vessel disruption: lymphatic vessel disruption (as in cases of trauma, or lymphoma) will lead to chylothorax. Blood vessel disruption will result in hemothorax. Pathogenesis of Pleural Fluid Formation The pathogenesis of pleural fluid accumulation can be summarized in the following table: Pathogenesis of Pleural Effusions A)Increased pleural fluid formation:  Increased interstitial fluid in the lung: Left ventricular failure, parapneumonic effusion, pulmonary embolus, ARDS, Post lung transplantation.  Increased intravascular pressure in the pleura: Right or Left ventricular failure, Superior vena caval syndrome (SVC), and pericardial effusion.  Increased pleural fluid protein level: parapneumonic effusion  Decreased pleural pressure (ex-vaco effusion). Lung atelectasis or increased elastic recoil of the lung.  Increased fluid in peritoneal cavity: Ascites, peritoneal dialysis, and Meig‟s syndrome.  Disruption of the thoracic duct: trauma, tumors (lymphoma) B)Decreased pleural fluid reabsorption:  Obstruction of the lymphatics draining the parietal pleura: Pleural malignancies  Elevation of the systemic vascular pressures: SVC syndrome or right ventricular failure. ●Disruption of the aquaporins system: a group of proteins that help transport water across the pleura ( still under investigation) General Causes of Pleural Effusions Table 1: causes of pleural effusions Differentiation Between Pleural Exudates and Transudates The most crucial aspect in reaching a diagnosis for pleural effusions is the differentiation between pleural exudates and transudates. Transudates are usually the result of systemic factors that influence the formation and absorption of pleural fluid. They are usually caused by conditions other than the lung and pleura (table 1). On the other hand, exudates are the result of pleural or pulmonary processes that lead to pleural fluid accumulation. In other words, they are the result of local disease. There are many laboratory tests that could help separate exudates from transudates. The most accepted and valid criteria for the diagnosis of pleural exudates are called Light‟s criteria. The application of Light‟s criteria requires the simultaneous analysis of pleural fluid and serum for protein content and LDH. Any pleural fluid that meets one of the following criteria is considered an exudate: iPleural fluid/serum protein >0.5 iiPleural fluid LDH/serum LDH >0.6 iiiPleural fluid LDH >2/3 upper normal serum level Any pleural fluid that doesn‟t meet the above criteria is considered a transudate. If the pleural fluid is a transudate, search cardiac, renal, or hepatic causes that may cause the effusion. The hard task remains for the pulmonologists to differentiate between the different causes of exudates. For this reason, several tests are required before reaching the exact cause of the effusion. 1- Appearance of the pleural fluid: A bloody exudate can be seen in cases of malignancies, pulmonary embolism, or may be due to traumatic thoracentesis. If the pleural fluid is deeply hemorrhagic, obtain a pleural fluid hematocrit. If the hematocrit is >50% of the peripheral blood, consider inserting an intercostal tube for a possible hemothorax. A turbid pleural effusion should be centrifuged and the supernatant fluid examined. If the supernatant appears clear, the pleural fluid is an empyema, while if it remains turbidly white, the fluid is a chylothorax. 2- Pleural fluid differential cell count: If neutrophils predominate the differential cell count, the process is an acute process, as in cases of parapneumonic effusions, pulmonary embolism, viral infections, malignancy, or early stage tuberculous effusion. If the effusion shows a predominance of mononuclear cells, the effusion is a chronic process as in cases of malignancy, pulmonary embolisation, tuberculous pleural effusion, or following CABG. 3- Pleural fluid glucose level: A pleural effusion with a low (<60 mg%) glucose level limits the diagnosis to four main diagnoses: parapneumonic effusion, malignancy, TB, or rheumatoid pleural effusion. Other rare causes include: paragonimiasis, Churg-Strauss syndrome, Urinothorax, and occasionally SLE. 4- Pleural fluid LDH: Pleural fluid LDH should be obtained every time a thoracentesis is performed for an undiagnosed pleural effusion. LDH is an indicator for pleural inflammation. If, with repeated thoracenteses, pleural fluid LDH level increases, the process is progressing and one should be more aggressive in pursuing a diagnosis. On the other hand, if LDH level decreases, the process is regressing and one can conserve and follow up. 5- Pleural fluid cytology: Cytological examination is a useful test in detecting malignancies in 40-70% of cases. Almost all adenocarcinomas of the lung may be diagnosed by cytology, while squamous cell carcinoma, lymphomas, and sarcomas are less commonly detected on cytological examination. The yield depends on the skill of the cytologist and on the tumor burden in the pleural space. 6- Pleural fluid marker for Tuberculosis: A- Pleural fluid ADA level: Adenosine Deaminase (ADA) is an enzyme produced by active lymohocytes. A pleural fluid level above 70U per L with a lymphocyte predominant effusion in a patient who doesn‟t have empyema of Rheumatoid arthritis is essentially diagnostic of TB pleural effusion. Levels above 40 U/L are suggestive of TB, while patients with ADA levels below 40 U/L are unlikely to have TB pleural effusion. B- Pleural fluid interferon Gamma levels: Interferon Gamma increases in patients with TB pleural effusion. Using a cutoff level of 3.7 U per ml is almost always diagnostic of TB effusion. Fig. 1: Fig. 2: Options When No Diagnosis Has Been Obtained After Initial Thoracentesis The first thing to order for a patient whose pleural effusion remains undiagnosed after the initial thoracentesis is a spiral CT scan of the chest to exclude or prove pulmonary embolism. Spiral CT will help identify a pulmonary embolus in a major vessel, as well as more clearly identify mediastinal lymphadenopathy, or pulmonary infiltrates. If still the diagnosis cannot be reached after CT, then there are five options for the pulmonologists: 1- Observation: This is a possible option if the patient is improving and there are no parenchymal infiltrates. If the condition doesn‟t improve, one should be more aggressive in reaching a diagnosis. 2- Bronchoscopy: This is a useful investigation if one or more of the following is present: (a) a pulmonary infiltrate is present, (b) hemoptysis is present (hemoptysis in a case of pleural effusion is very suggestive of an endobronchial lesion), (c) the pleural effusion is massive (occupying more than three fourths of the hemithorax), or (d) the mediastinum is shifted towards the side of the effusion (possibly an endobronchial lesion is present). 3- Thoracoscopy: This is the most accurate method of diagnosis if the necessary equipment and expertise are present. The procedure is minimally invasive, highly specific, and can be performed in patients with poor general condition who are not fit for general anesthesia and open biopsy. 4- Needle biopsy of the pleura: Needle biopsy of the pleura can reach a diagnosis in processes that affect the pleural space uniformly (TB or mesothelioma), while in metastatic cases where the pleural metastasis are in the form of nodules separated by areas of normal pleura the yield of this procedure is very low. Special expertise are needed to obtain adequate samples of the pleura as well as skilled pathologists. 5- Open pleural biopsy This is the most accurate diagnostic method, although it is the most aggressive. In the presence of medical thoracoscopy, open pleural biopsy is becoming less preferred. Although it has the highest yield, there is an incidence of failure of thoracotomy to reach a diagnosis. Considerable mortality and morbidity are associated with the procedure. Medical Thoracoscopy Thoracoscopy was used first used as a diagnostic tool by HC Jacobaeus in 1910, but it soon also was used as a therapeutic technique for lysis of pleuropulmonary adhesions. By means of thoracocautery, Jacobaeus divided the adhesions holding the lung to the chest wall to facilitate pneumothorax treatment of tuberculosis (Jacobaeus‟ operation). Later, the addition of the term “Medical” was necessary to distinguish the procedure from the more invasive intervention requiring general anesthesia, double lumen endotracheal tube, and multiple points of entry “Surgical Thoracoscopy” or Video Assisted Thoracoscopic Surgery (VATS). Medical thoracoscopy can be performed with or without video assistance, under local anesthesia and conscious sedation, in an endoscopy suite, using non-disposable instruments. It is therefore considerably less invasive, with less morbidity, and less expensive. Medical thoracoscopy is now mainly a diagnostic tool but has some therapeutic capabilities. Pleural effusions are the leading indication for medical thoracoscopy, both for diagnosis (mainly in exudates of unknown etiology and for staging of malignant mesothelioma or lung cancer) and for treatment by talc insufflation for pleurodesis in malignant or other recurrent pleural effusions, or in cases of empyema. Spontaneous Pneumothorax is an excellent indication for both diagnostic as well as for therapeutic medical thoracoscopy. For those who are more familiar with the technique, other indications for thoracoscopy are biopsies from the diaphragm, the lung, the mediastinum, and the pericardium, as well as thoracoscopic sympathectomy, and local management of spontaneous pneumothorax. In this section, the pleural applications will be discussed. Historical Background: Hans-Christian Jacobaeus, an internist working in Stockholm, Sweden, in 1910 introduced thoracoscopy at the same time as laparoscopy in a paper entitled „Concerning the possibility of using cystoscopy in the examination of serous cavities‟. He reported two cases of exudative pleural effusions in which, after aspirating the pleural fluid and replacing it with filtrated air, he performed thoracoscopy under local anesthesia. He found that “examination of the pleural cavities was of particular interest, not in the least because they were only to a limited degree suitable for a surgical approach”. In addition to the diagnostic aspects, Jacobaeus hoped to gain prognostic information from the procedure. During the ensuing years, thoracoscopy was used for diagnostic purposes by some other pulmonologists mainly in Scandinavia, Germany, Italy, and other European counties. In 1925, Jacobaeus published his vast experience in thoracoscopy, describing in detail his studies of the etiology and staging of tuberculous pleurisy, of malignant pleural effusion, rheumatoid pleurisy, parapneumonic effusion, as well as idiopathic pneumothorax. Indications of Diagnostic Thoracoscopy Pleural effusions Pleural effusions of unknown etiology are the main indication for diagnostic thoracoscopy. A large study comprising 1000 consecutive patients with pleural effusions showed that after extensive workout of pleural fluid analysis and closed pleural biopsies (needle biopsy), 215 cases remained undiagnosed (21.5%). After thoracoscopy, the number of left undiagnosed effusions was 40 (4%). Malignant pleural effusions: Malignant pleural effusions (MPEs) are today the commonest indications for both diagnostic and therapeutic thoracoscopy. Thoracoscopy is a very sensitive tool for diagnosing MPEs which may defy diagnosis using cytological examination and closed pleural biopsies for months. Many investigators who were conservative regarding the use of thoracoscopy for diagnosing a suspected MPE and claiming that at some point of time the diagnosis will become evident, are now reconsidering because waiting is detrimental to the patient, and because the delay in diagnosing reduces the likelihood that a therapeutic pleurodesis may be effective. As time passes, the tumor load increases and the invasion of the visceral pleural results in a condition termed “trapped lung” that causes an irreversible functional deficit. It has also been proven that gamma interferon, one of the few agents to show action in malignant mesothelioma, is only effective if administered early in the disease process. Thoracoscopy can reveal the features suggestive of malignancy morphologically by their appearance: nodules 1-5 mm in diameter, larger polypoid masses, localized tumor masses; rough, pale, thickened pleural surfaces; and hard, poorly vascularized pachypleuritis. The diagnostic sensitivity of thoracoscopy is similar in all types of pleural malignancies, whether of lung origin, extrathoracic malignancies, and in diffuse malignant mesothelioma. Medical thoracoscopy in metastatic lesions of the pleura has the advantage of obtaining samples under direct vision from the diaphragmatic and the visceral pleurae, and obtaining larger samples which help in easier identification of the primary tumor and determination of hormone receptors in breast cancer cases. The extent of intrapleural spread can be described using a scoring system which has shown close correlation with survival. The main advantage of using thoracoscopy for diagnosis of metastatic malignancies to the pleura is the possibility of performing thoracoscopic talc insufflation (TTI) during the procedure to produce an effective pleurodesis. The is the most acceptable conservative option for pleurodesis nowadays because of its high success rate (>90%), even in cases of lymphomatous chylothorax where all other measures may fail. For details of the procedure, please see later. Tuberculous pleural effusion Although the diagnostic yield of pleural fluid cultures for TB and closed needle biopsy combined is quite high, there may be indications for medical thoracoscopy in otherwise uncertain pleural effusions. The diagnostic accuracy of thoracoscopy approaches 100% because the pathologist and the lab are provided with multiple, selected biopsies resulting in a more frequent pathological and mycobacteriologic proof. The early diagnosis that medical thoracoscopy provides has resulted in the diminution of cases that developed fibrothorax due to longstanding TB pleurisy in the centers that routinely use medical thoracoscopy in undiagnosed pleural effusions, as opposed to observation. The procedure helps in more complete drainage of the fluid, and division of loculations which hamper the total expansion of the lung. Other pleural effusions In cases of pleural effusions that are neither malignant nor tuberculous, thoracoscopy may give macroscopic clues to the etiology (e.g., in rheumatoid effusions, effusions following pancreatitis, liver cirrhosis, extension from the abdominal cavity, or trauma). Although in thee entities history, pleural fluid analysis, physical and other examinations are usually diagnostic, thoracoscopy may be indicated in those cases where a definite diagnosis could not be reached. When the effusion is secondary to underlying lung pathology such as a pulmonary infarct or pneumonia, the diagnosis can be obtained macroscopically and confirmed microscopically from lung biopsies. As already mentioned, thoracoscopy is well suited for diagnosing BAPE, which, by definition, is a diagnosis of exclusion. In other conditions where the diagnosis is unknown, the main advantage of thoracoscopy is to exclude the possibility of malignancy and tuberculosis. By means of thoracoscopy, the proportion of the so-called idiopathic pleural effusions usually falls markedly below 10%, whereas studies that did not use thoracoscopy report a 20% incidence of idiopathic pleural effusions. In rare occasions, the performance of thoracoscopy can be impossible due to the presence of dense pleuropulmonary adhesions. These dense adhesions are the result of – most probably- repeated diagnostically fruitless aspirations of large volumes of pleural fluid. For these cases, the reader is referred to the section on extended thoracoscopy when discussing the technique of thoracoscopy. Empyema During the exudative phase of empyema, effusions are characteristically thin and adhesions have not been formed. In this stage, the fluid can be drained with a chest tube. Beyond this stage, however, fluid is thick and multiple adhesions are formed, resulting in loculations. Thoracoscopic visualization may allow debridement of fibrinoid adhesions and permit evacuation of loculated fluid. Thoracoscopy can allow complete evacuation of purulent empyema. After removal of pus from the pleural cavity, adhesions are dissected to form one large cavity. Placement of a large caliber chest drain in a clean adhesion-free cavity ensures the best chances for lug re-expansion, with the aid of negative pressure applied through the chest tube. Therefore, to benefit most from the procedure, it should be performed as early as possible before the adhesions are too fibrous and adherent. Irrigation of the pleural space during the procedure has been tried. The procedure has been found beneficial especially when the irrigation is continued daily through two chest drains until the aspirated fluid is culture negative. This method has shortened hospital stay and avoided thoracotomy. In conclusion, if chest tube insertion is indicated in cases of complicated parapneumonic effusion, and if the facilities are available, medical thoracoscopy should be performed at the time of chest tube insertion to gain benefit from the procedure. Spontaneous pneumothorax In spontaneous pneumothorax, medical thoracoscopy can be applied easily for diagnostic as well as therapeutic purposes, if the facilities and the expertise are available. At the time of insertion of the chest tube, introduction of a thoracoscope will help stage the disease visually according to the classification of Vanderschueren: stage I: endoscopically normal lung; stage II: pleuropulmonary adhesions; stage III: small bullae and blebs (<2cm diameter); and stage IV: numerous large bullae (>2cm diameter). Medical thoracoscopy for spontaneous pneumothorax offers the possibility of combining chest drainage with coagulation of blebs or bullae as well as pleurodesis using talc poudrage. In cases staged visually as stage IV (numerous large bullae), the patients should be transferred to surgical department directly after insertion of the chest tube. Only if the conditions are unfavorable for surgical intervention (e.g., respiratory insufficiency, secondary to severe airway obstruction or other advanced pulmonary diseases), stage IV bullae are coagulated or talc poudrage is performed. Generally, medical thoracoscopy is justified in all patients with spontaneous pneumothorax where tube drainage is indicated, since several advantages are offered: precise assessment of underlying lesions under direct visual control, choice of best treatment strategies (conservative or surgical), direct treatment by coagulation of blebs and bullae, and by severing adhesions if necessary, as well as selection of the best site to place the chest tube. Diagnostic Thoracoscopy: Equipment and Technique. The use of thoracoscopy has been resumed as a result of considerable progress in modern techniques, particularly in the following areas: (1) Endoscopic telescopes have been greatly improved, and now have an extremely high optical quality despite their small diameter, (2) Adequate instruments, including video camera, forceps, endoscopic scalpels, staplers, and laser, and (3) Progress in anesthesia allowing for a broad choice of agents that range from local anesthetics in outpatients to general anesthesia. Clinical prerequisites: With the rare exceptions of tension pneumothorax and massive pleural effusion, in which emergency therapeutic pleural drainage can be performed at the same time as diagnostic thoracoscopy, this procedure should be considered only after careful evaluation aimed at answering specific questions. The history reveals information about the acute or chronic nature of the disease, effort intolerance and possible underlying extrapulmonary disease such as tumor, deep venous thrombosis, congestive heart failure, myocardial infarction, renal insufficiency, pancreatitis, liver cirrhosis, etc. it is well known that the lung and the pleura may be involved in many diseases. It is of particular importance to inquire about previous treatment with cytotoxic agents, radiotherapy, or previous antibiotic therapy. Thoracoscopy is contraindicated in patients with severe coagulation defects or those on anticoagulant therapy. Radiological evaluation routinely involves a postero-anterior and lateral chest xray, frequently supplemented by CT scan. In cases of suspected pulmonary embolism, ventilation-perfusion scintigraphy and high resolution CT scan may be advised. In patients with diffuse lung disease, radiological examinations will assist in deciding the hemithorax on which thoracoscopy should be performed. Practically, radiological examination determines the optimum point of insertion of the thoracoscope. Evaluation of the respiratory status requires, as a minimum, arterial blood gases (ABGs) analysis. An electrocardiogram should be done to exclude recent myocardial infarction or significant arrhythmia. The clinical chemistry laboratory should provide the physician with thromboplastin time, serum electrolytes, blood glucose levels, blood group typing, platelet count, liver function, rheumatoid factor anti-nuclear antibody, or serum amylase. The results of pleural fluid should be available and include: chemical analysis (LDH, sugar, protein content, and ADA), cytological examination, and microbial cultures. If the physician has convinced himself that thoracoscopy is indicated, he should have little difficulty explaining the need for the procedure to the patient obtaining an informed consent. Patients may be provided by a hand-out followed by a verbal explanation of the procedure including methodology, management of post-operative pain and other so-called typical complications as well as the expected diagnostic and therapeutic results. Equipment for thoracoscopy: 1-Telescopes: A- Rigid telescopes: the rigid thoracoscope with cold light source id the instrument that is most widely used. Its design must satisfy two requirements: (1) to make high quality visual exploration and faultless photographic or video documentation, and (2) to facilitate multiple, large biopsies of sufficient size to ensure definitive histopathologic diagnosis, while accommodating electrocautery and/or YAG laser cautery when necessary. B- Flexible fiberoptic thoracoscopes: flexible thoracoscopes have been used with controversies regarding its effectiveness. Some operators have used these instruments because the rigid instruments were not available and others have found it extremely useful. The size of the biopsies obtained by the flexible endoscopes is small and may make the diagnosis of such cases as mesothelioma very hard. C- Semiflexible thoracoscopes: these are the innovation in the endoscope technology that is now getting more and more popularity. These scopes have a rigid shaft and a flexible tip that allows for a more complete examination of the pleural cavity. Some models have a working channel and these are easiest to work with, while some other models have no working channel and necessitate a second port of entry for the biopsy forceps. 2-Trocars: Trocars consist of an obturator and a cannula. To make the examination easier, Trocars should not be too large. Trocars of the 12 mm and even the 10 mm diameter are somewhat difficult to manipulate in all directions especially when the intercostal spaces are narrow. The examination may be limited due to pain caused by the trocar pushing against the ribs. The optimum size of the trocar therefore should be 7mm in diameter and about 100mm in length. A second trocar 5x100mm that is electrically insulated to avoid burns to the chest wall should be used when applying electrocautery. 3-Forceps: The 7mm optical forceps for biopsy under direct vision using a single point of entry is ideal for sampling the parietal pleura. A 5mm coagulating forceps is used for obtaining biopsies via a second point of entry through a 5mm trocar. It is essentially useful for collecting samples from the diaphragmatic pleura; thick, hard, or fibrous pleural lesions including asbestotic pleural plaques; and the visceral pleural and lung. 4-Auxilliary instruments and accessories:  Sheets, clamps, sterile gowns for the practitioner and his assistant.  Needles, syringes, and cupula for the local anesthetic agent.  Scalpels, compresses, sutures, and anionic surfactant to prevent the formation of mist in the lens surfaces (“anti-fog solution”).  Plastic aspiration tubes, 4mm and 6mm in diameter.  Swab  Talc atomizer.  Pleural drainage tubes (chest tubes) between 20F and 32F.  Guide for the chest tube or a self-contained chest tube set.  Light sources, cold light cables.  Video camera, videotapes.  Manometer to measure pleural pressure. The endoscopy room: Thoracoscopy can be performed either in an operating theater or in an endoscopy suite. The suite must ideally contain the following:  A thoracoscopy table: this may e a simple operating table or, ideally, may have a height adjustment and a back that can be raised for operating in the semi-sitting position. Some tables can be adjusted laterally along the longitudinal axis that allows the patient to be repositioned easily. Such sophisticated tables are very helpful not really essential.  Aspiration equipment for the pleural fluid, with 2-liter or more collecting bottles connected to negative pressure.  Anesthetic equipment, with air feed and oxygen supply.  An overhead light with adjustable brightness.  A Mayo stand placed sideways across the table to hold the instruments.  A 150-Watt high frequency (HF) scalpel for electrocautery, or a Neodymium: Yttrium Garnet (Nd:YAG laser) laser.  Separate mobile carts for endoscopic light sources, photographic equipment, films, and videos.  A stool.  A cupboard or drawers for instruments. The endoscopic area should be, like other operating areas, bacteriologically clean ventilated with filtered air. Floors and walls should be seamless and washable. Cleanliness requirements are greater than endoscopy via natural body orifices, for example bronchoscopy, but less than in cardiac catheterization. Thus, thoracoscopy is best performed in rooms used for lapaoscopy or operating rooms. A premedication area, a washroom for personnel and an area for cleaning and sterilizing instruments should be provided. Personnel: The personnel required to required to perform thoracoscopy include an endoscopy nurse or an endoscopy assistant for the instrumentation, an additional circulating assistant who is not sterile, the physician who performs the procedure and, if possible, an additional physician assistant. In an emergency, thoracoscoy can be performed with only a physician and a nurse but this is less efficient and prolongs the duration of the procedure. Thoracoscopy technique: Induction and monitoring of pneumothorax: The indication of inducing pneumothorax varies according to the prethoracoscopic condition e.g., pleural effusion, previous pneumothorax, pr a normal pleural space. In the presence of a pleural effusion, an open needle puncture should be performed at the level of greatest opacification or dullness. When the syringe is removed from the needle, the pleural fluid will come out (due to increased intrathoracic pressure) or air will be heard being sucked through the needle if the intrapleural pressure is negative. Air can be injected from a syringe, or even better, CO 2 under slight positive pressure from a pneumothorax apparatus. The pneumothorax can be fluoroscopically monitored, and ideally, it should measure 10 cm in diameter on antero-posterior and lateral views. Alternatively, in the presence of massive effusion, the thoracoscope can be directly introduced without induction of pneumothorax although this carries a greater risk of lung injury. In the presence of a preexisting pneumothorax, fluoroscopy should be performed in the lateral position in order to find the best point of entry for the trocar and to establish the position of the diaphragm. Occasionally, addition gaseous medium may be added. If neither effusion nor pneumothorax is present, an artificial pneumothorax must be induced using the technique of Forlanini. For this purpose, many types of pneumothorax needles have been developed including the oldest blunt Saugmann cannula with mandarin, stopcock and side hole. Other needles like the blunt Salomon cannula with side hole, or the cannula developed for laparoscopy that has an inner blunt cannula that springs forward as soon as the peritoneum or pleural space have been penetrated can be used, but less effectively. The most commonly used needles are the pneumothorax needles developed by Denecke (it has a slit like hole just proximal to its tip and can be introduced even without local anesthesia) or the Boutin needle (which has a soft, atraumatic tip that will enter the pleural cavity with the least risk of injury). Any of these needles can be connected to a pneumothorax apparatus for injecting CO 2 gas or to a syringe for injecting air. The pneumothorax apparatus operates according to the principle of communicating tubes and utilizes a water manometer. It is very simple and even more sensitive and user-friendly than the electronic instruments auch as those used for pneumoperitoneum. The best site for induction of pneumothorax is the mid-axillary region between the 3rd and the 5th intercostal spaces as here, the intercostal vessels are protected by the rib margins. Induction of a pneumothorax can take place on table at the time of thoracoscopy; but some physicians prefer to induce pneumothorax on the day before the procedure by injecting 300-500 ml of gas intrapleurally. This allows time to review the radiographs to chose the most appropriate site of entry for the thoracoscope. In any case, the intrapleural pressure must remain negative. A positive pressure may cause Mediastinal shift, compromise cardiovascular performance, and be painful to the patient. Position of the patient: The patient must be comfortably installed in lateral position with the healthy side down. A rolled-up sheet is placed under the patient‟s thorax to spread apart all the intercostal spaces on the exposed side of the chest. The head is lowered and the arm attached at right angle to the head of the head with gauze or a sling to a bar. The patient should be grounded by placing a metal plate between the table and one buttock if electrocautery is to be used. The physician usually faces the patient while the assistant is across the table behind the patient‟s back. Anesthesia: Local anesthesia is the preferred method as long as the thoracoscopy procedure is to be brief in a patient whose pleural cavity is free of adhesions. Local anesthesia is also preferable in high risk patients exhibiting poor general condition, compromised respiratory function, or cardiac insufficiency. General anesthesia may be required in some cases and it is the technique of choice for procedures requiring double-lumen intubation and lung immobilization. This method gives is favorable for both the physician and the patient because it allows time for multiple biopsy collection, section of extensive adhesions, and electrocautery as well as high quality photography and video filming. The “conscious sedation” technique or light anesthesia is simple and has practically no contraindications. The technique consists of local anesthesia and neuroleptanalgesia with modern drugs that combine properties of sedation, analgesia, and amnesia. Suitable neuroleptanalgesics include midazolam (the most commonly used), propofol, pethidine, diazepam, and fentanyl. Performance of thoracoscopy ► First point of entry: An axillary point of entry is selected in most cases. The axillary triangle has no large muscles that could obstruct the passage of the instruments. The axillary triangle is bounded anteriorly by the lower edge of the pectoralis major muscle, posteriorly by the edge of the latissimus dorsi muscle, and inferiorly at the level of t diaphragmatic    insertions. Its apex reaches the second intercostal space. The point of entry is generally near the mid-axillary line, within this triangle and is selected as follows: In the third or fourth intercostal space in patients with spontaneous pneumothorax because the leak is usually in the upper lobe. In the 5th, 6th, or 7th intercostal space for pleural effusions. The last two spaces are preferred when metastatic tumor and mesothelioma are suspected, to reach the most common sites for those malignancies. This entry provides an excellent view of both the diaphragm and the costovertebral gutter. In the 4th or 5th intercostal space for pulmonary biopsies so that all lobes can be reached quickly and easily. One must be aware that a pleural lesion that is too close to the point of entry cannot be biopsied with a rigid thoracoscope, but can be dealt with using a flexible instrument. These lesions would be easier to approach through an incision 10-12 cm further. Every effort should be made to precisely identify the level of the lesion on the roentgenograms so the appropriate intercostal space could be used for the point of entry. ►The second point of entry: The second point of entry is established quickly and easily. Its position is determined by viewing through the 50° scope while depressing the possible entry site with the index finger. The resulting depression can be easily viewed from inside the thorax. Sometimes it is helpful to actually insert a needle through that site while viewing the precise location through the scope. After administering the local anesthetic, a 5-mm incision is made and the 5-mm trocar is inserted directly. This trocar and the forceps used should be insulated so as to allow the use of electrocautery or laser. ► Points of entry for specific localized regions: In unusual situations, other points of entry are used, depending on the clinical setting or the roentgenograms. A pleural lesion that is too close to the point of entry cannot be reached and biopsied with a rigid scope. Thee lesions are better approached from the opposite side. Therefore, for posterior lesions one would ideally place the trocar in the anterior axillary line, while for anterior lesions the posterior axillary line best chosen. Lesions on the lateral aspect of the costal pleura would best be reached through ports placed in the midclavicular line. It is needless to mention that the flexible and semiflexible instruments are superior in dealing with such lesions. ► Introduction of the trocar: With a scalpel, a vertical incision is made through the skin and subcutaneous tissue, appropriate to the size of the trocar to be used. The handle of the trocar is held firmly in the palm of the hand while the extended index finger limits, for safety‟s sake, the depth of the depth of insertion. The approximate distance from the kin to the pleural space can be estimated by the local anesthetic needle, while applying the local anesthetic. Under difficult circumstances, the needle should be left in the chest wall and the trocar can be inserted parallel to it. While fixing the intercostal pace with two fingers, the trocar is advanced with a fairly forceful corkscrew motion until the detectable resistance of the internal thoracic fascia has been overcome. The tip of the trocar should lie 0.5 cm inside the pleural cavity. Pleural effusions should be completely removed prior to inserting the scope. This can be done without risk because, as the fluid is removed, it is substituted rapidly with ambient air that provides pressure equilibration. ► Endoscopic visualization and anatomy: After completely removing the effusion, orientation is simple although visualization of the pleural space may be made difficult, if not impossible, by inflammatory, Fibrinous pleural thickening; adhesions and fibrous bands; inflammatory exudates with empyema; or extensive tumor overgrowth obscuring the lungs, chest wall, diaphragm and mediastinum. Anatomical relationships and intrathoracic structures are usually very well identified during thoracoscopy. Cases of pneumothorax requiring thoracoscopy are ideal for examining intrathoracic structures and to observe the normal parietal pleura, pleural vessels, and the underlying intercostal muscles and ribs. To prevent the lens from becoming fogged up, the tip of the thoracoscope can be immersed in demineralized sterile water at 70-80°c. The optics and light source should be dried with a sterile cotton ball and wiped dry. Inside the right pleural cavity, orientation can be achieved by locating the point at which the three lobes meet: the junction of the oblique and the horizontal fissures. On the left side, the oblique fissure can be used for orientation. The diaphragm can be recognized because of its respiration-related movements. Ribs, intercostal muscles, fat, blood vessels, and nerves are usually readily distinguishable. The position of the large vessels such as, on the lest side, the aorta and the subclavian artery and on the right, the vena cava and the innominate vein as well as the subclavian artery are readily recognizable. The heart and great vessels are identified because of their pulsations, which are occasionally transmitted to adjacent parts of the lungs. If fibrous bands or adhesions are present, these should be avoided. Torn and bleeding adhesions can be cauterized by means of diathermy and served if desired. Delicate spider-web adhesions that are not vascularized can be separated or removed with the forceps. Endoscopic visualization of the parietal pleura: Visual exploration of the pleura is carried out in few minutes. It is done by rotating the scope to explore the whole pleural cavity after dissecting adhesions. There are always two levels of observation using the scope: from a distance of 5 -10cm to obtain a wide-angle view with weak magnification; and then a close magnified view at a distance of 1-2cm to insect the pleural cavity very carefully and to select the best biopsy site. In its normal state, the pleura is transparent allowing visualization of many structures through it, including the ribs, the parietal vascular pattern, the diaphragmatic insertions and central tendon, the pericardium with its attendant fat, the fibrous or fatty tissues of the pleural dome, the sympathetic trunk, the intercostal vessels, etc. Variable amounts of anthracotic pigment can be present within the parietal pleura, especially posteriorly and in the costovertebral gutter. These are often linear canalicular, or corresponding to the underlying lymphatics, or they may be punctiform like the lymphatic formation that was described by Kampmeier and named after him (Kampmeier‟ foci). Fatty collections are often abundant in the pleura, especially in obese people. These may take the form of long yellowish brownish plaques located long the ribs, in the apex, in the anterior mediastinum around the pericardium and on the diaphragm. ● Abnormal pleura: One of the hardest tasks of the endoscopist is to distinguish between innocuous and malignant or tuberculous “inflammation”. In fact, it is often impossible to tell the difference just by looking, since invasive cancers may sometimes look like a simple inflammation. Simple inflammation is usually redder with a smoother, more regular surface and is more edematous than malignant pachypleuritis. When biopsies are taken, the forceps will cut a clear section of malignant tissue, whereas it easily pulls away much larger sections of inflamed pleura. However this difference is only a matter of degree, and many biopsies (up to 15-20) should be taken to be certain that the pathologist as representative samples of the lesions that had been observed. ● Non-specific pleural inflammation: can be found in different stages: i- Mild: a simple increase in normal pleural vascularizature, giving the pleura a pinkish hue; it is still thin and transparent. ii- Intense: the pleura is bright red with engorged blood vessels and subpleural edema. The serosa become opaque and the outline of the ribs and intercostal vessels can no longer be seen distinguished. The pleura can be up to 3-5mm thick. These changes are often more prominent in the costovertebral gutter and on the diaphragml as the pleura is viewed upwards, frequently the pleura thins out, has progressively less reddish discoloration, and finally may look completely normal at the apex. iii- chronic: in long-established pleurisies, the pleura maintains it thickness, but has a white or grayish tinge; it is opaque as a result of invasion by fibro-elastic and collagenous tissue. ● Specific pleural lesions: The following three patterns can be distinguished as opposed to non-specific inflammation: iLymphangitis appears as fine reticular pattern covering all or part of the pleura ii- Tuberculous or sarcoid granulomata 1-3mm in diameter. In sarcoidosis, they are much common on the parietal pleura. iii- Malignant nodules, which are variable in size and shape, usually predominate inferiorly. Also, asbestotic plaques, which are thick, pearly white, fibrohyaline or calcified pleural lesions that are often found in asbestotic effusions. In these cases, thoracoscopic pulmonary biopsy may reveal high concentrations of asbestos fibers. Positioning of the chest tube for pleural drainage At the end of thoracoscopy, a chest tube is inserted through the point of entry. The tube is mounted over a 50cm rigid blunt guide and inserted through the point of entry. The tube is inserted perpendicular at first, and then directed in the desired direction until it meets the chest wall. No special force is required. Ideally, the tube should be directed posteriorly and then as close to the apex of the pleural cavity as possible. When thoracoscopy is performed for pneumothorax or for pulmonary biopsies, the tube can be removed shortly after radiological confirmation of lung re-expansion. In cases of pleural effusions, the tube is left in place for several days until the drainage provides less than 100 ml of fluid per day. The performance of thoracoscopic talc insufflation during the procedure reduces the postoperative hospital stay. Securing of the chest tube with silk sutures to the skin should be done to prevent the tube from slipping. An additional pure string suture is placed and left open until the time of removal of the tube, when it is tightened to be removed 7-10days later. Thoracoscopy: Complications and Contraindications Thoracoscopy is one of the safest in the interventional pulmonology procedures. The mortality was found to be 0.09% in a cohort of 4300 thoracoscopies. A- Potential complications: 1Any perioperative incidents (trocar injury, intercostal injury) that may require immediate thoracotomy. 2Air leak of more than one week after intervention, 3Air leak requiring re-intervention or thoracotomy, 4Bleeding greater than 50 ml or requiring blood transfusion, 5Respiratory failure more than 24 hours after intervention, 6Pneumonia, 7Post-procedure effusion with suspected infection prompting drainage or hospitalization, 8Onset of newly developed pneumothorax resulting in symptoms or requiring insertion of a chest tube, 9Pulmonary embolism or deep venous thrombosis, 10Onset of new chest pain, arrhythmias, or myocardial infarction, 11Improperly placed chest tube requiring repositioning, 12Atelectasis prompting bronchoscopy. B-Potential minor adverse events: 12345- Temperature greater than 0.5°c above baseline for at least 48 hours after thoracoscopy, Clinically significant subcutaneous emphysema, Wound infection, New clinically significant pneumothorax, Paraesthesia or lateral chest wall discomfort lasting 30 days or more. The five unacceptable disasters of thoracoscopy can be summarized below: 1Wrong side: a patient, who was operated on the wrong side, conjured up immediate visions of massive negligence. 2Kebab lung: this occurs when an ill-directed trocar is inserted in the lung. 3Clotted hemothorax: a patient –victim of a road traffic accident- was referred for thoracotomy after unsuccessful intercostal drainage. On opening the chest, a green structure presented that was mistaken for a gangrenous lung. That was the gall bladder. The trocars had been transfixing the misplaced liver in a traumatic diaphragmatic hernia. 4Artificial lunchothorax: this occurs when a distended stomach in a paraesophageal hernia is mistaken for a hydropneumothorax. 5Aorto-pleuro-cutaneous fistula: this is the most dramatic of the disasters. A registrar had forgotten the Mediastinal shift while trying to drain an infected postpneumonectomy space. This resulted in disastrous bleeding. Contraindications to thoracoscopy: A) Absolute contraindications: There are only a few absolute contraindications, the principal one is insufficient space in the pleural cavity. The minimum space required for the insertion of the thoracoscope is 10cm in diameter. Also, absolute contraindications include: honey comb lung, pulmonary arteriovenous malformation, suspected hydatid disease, and highly vascularized pulmonary lesions. B) Relative contraindications: These are related to the general health of the patient, and a careful risk/benefit analysis at the time of thoracoscopy is considered. Fever, cough, hypoxemia, hypocoagulable state, unstable cardiovascular status, etc may all prevent the procedure temporarily.