The fexible bronchoscope is the main source of diagnosis in sarcoidosis, even by using conventional forceps for the biopsy. A high degree of diagnostic accuracy is achieved if more than four samples are taken. The distribution of ­granulomas along pulmonary lymphatic routes is frequent and bronchial lesions can be sampled directly with the cupped forceps. It has been shown that TLB samples can detect granulomas even when radiological ndings fail to reveal lung parenchymal disease [37]. Some cystic interstitial lung diseases can also be diagnosed by either TLB or TLB-C. Langerhans cell histiocytosis is an air- way-centered disease, and TLB can identify the typical histological lesion. The performance of immunohistochemical stains for Langerhans cells (S100 protein and CD1a) is not required when histological ndings are characteristic. On the other hand, in linfangioleiomiomatosis (LAM), immunohistochemical staining may be useful even if de nite lesions are not seen [33, 38]. LAM cells are eosinophilic on hematoxylin- eosin-stained sections and HMB-45 immunohistochemical stains con rm the diagnosis.

Some studies that evaluate the diagnostic yield of TLB-C in ILDs show a range of 50–100% (depending on the cohort), with an excellent agreement in the context of a multidisciplinary team evaluation [16, 36, 40–47]. So, the probability to achieve an accurate diagnosis for ILDs is clearly higher by using transbronchial cryoprobes than by conventional forceps [36]. Furthermore, a prospective, multicenter study investigating diagnostic agreement between TLB-C and SLB showed high levels of concordance for both histopathological interpretation and multidisciplinary discussion (MDD) diagnoses supporting the clinical utility of TLB-C in ILDs’ diagnostic algorithms (Table 37.1) [16]. Consequently, in most expert centers for transbronchial cryobiopsy, this new tool has replaced the conventional TLB. Complications of TLB-C include pneumothorax in 0–26% and bleeding in 0–42% with a very low mortality rate of 0.3% [16, 36, 40–47]. Severe bleeding, exacerbations, respiratory infections, and persistent air leak are rare [16, 40–47].

Technical Advises for Conventional TLB and TLB-C in ILD

Another determinant for the utility of TLB in ILD is the technical procedure [31]. Biopsies from two different segments from the same lung can be obtained, but biopsy specimens from both lungs are contraindicated. After introducing the bronchoscope until a segmental bronchus, the forceps or cryoprobe is distally introduced.

In conventional TLB, the patient is asked to inhale, and the forceps are opened. The patient is then asked to exhale, and, at end-expiration, the forceps’ jaws are closed. If the patient experiences pain at this point, the forceps is opened and withdrawn because the only pain-sensitive structure in the area is the visceral pleura. Approximately four to six biopsies are the ideal number for pathologists, although this number of samples is not always possible due to many reasons.

In TLB-C, the patient requires deep sedation to avoid cough, an endotracheal tube is required to protect the upper airway (rigid or semi-rigid), three to ve biopsies should be obtained with fuoroscopic guidance to place the probe 1 cm from the visceral pleura, and an endobronchial blocker or a Fogarty balloon is required for selective bronchial blockade in case of bleeding [42]. Ideally, the procedure requires two bronchoscopists and nurses, anesthesiologist, and the adequate installations to perform the procedure in a safe manner. Safety considerations and contraindications regarding how to perform TLB-C have been described (Table 37.2) [42].

The main complication of conventional TLB and TLB-C is bleeding, which is the primary limiting factor in obtaining more or larger biopsy samples. Less frequent complications are pneumothorax, hypoxemia, or cardiac arrhythmias during the procedure. Although less common, pneumothorax may induce signi cant deterioration in lung brosis. The risk of pneumothorax is infuenced by functional impairment, brotic HRCT score, and UIP pattern [47]. It frequently occurs if the evaluation of the pleural–subpleural area is the objective (as for UIP) [16]. Usually,

Table 37.2  Contraindications, safety, and technical issues regarding TLB-C

Contraindications and safety considerations

 1.  Major risks after TLB-C are pneumothorax and bleeding

 2.  Bleeding diathesis and anticoagulant therapy, treatment with thienopyridines or other new antiplatelet drugs, and thrombocytopenia with platelets <50 × 109/L should be considered as contraindications

 3.  Pulmonary hypertension may increase the bleeding risk and is therefore considered as a relative contraindication

 4.  No age limits are suggested

 5.  b forced vital capacity (FVC) <50% and lung capacity for diffusion of carbon monoxid (DLCO) <35% of the predicted values are regarded as relative contraindications

How should TLB-C be performed?

 1.  TLB-C should be performed in patients under deep sedation or general anesthesia, with a proper airway control (laryngeal mask airway, endotracheal tube, or rigid bronchoscope)

 2.  If a fexible endotracheal tube is used for airway management, an endobronchial blocker or a Fogarty balloon should be used prophylactically to control bleeding and prevent central airway blood fooding. In case of intubation with a rigid bronchoscope, prophylactic balloon placement may be helpful, but is not felt to be mandatory

 3.  It is suggested to obtain three to ve biopsies,

1 cm from the visceral pleura, and fuoroscopic guidance be used

 4.  TLB-C should be performed by interventional bronchoscopists trained at a center with experience in the management of potential complications like bleeding, pneumothorax, or respiratory failure

 5.  TLB-C should be performed in the operating room with full anesthesia support or in a dedicated bronchoscopy suite with emergency equipment immediately available with possibility to admit the patient to the intensive care unit and escalate care if needed

DLCO, FVC, TBL-C transbronchial lung cryobiopsy

fuoroscopic guidance for a correct placement of the forceps or cryoprobe is effectively used to reduce the rate of pneumothorax.

Conventional TLB is a safe procedure that does not require general anesthesia, with an overall mortality of 0.1%, and can be performed as an outpatient procedure. Bleeding occurs to some degree in virtually all TLB procedures, and in some cases can be substantial. Bleeding is a

major concern because of the limited options available to manage excessive bleeding through the fexible bronchoscope. The suction channel is millimetric and the volume of blood that can be suctioned is limited; also, visibility is impaired as blood obscures the lens. Moreover, because the entire tracheobronchial tree is only about 150 mL in volume, a relatively small amount of blood can produce major problems with oxygenation [31].

TLB-C presents a variable probability of pneumothorax (mean of 12%) and bleeding (mean of 39%), with higher severity (grades 2–4) [40]. However, the fact of performing this procedure under an endotracheal tube and the possibility of controlling bleeding through angioplasty balloons selectively located in the distal bronchi allow decreasing morbidity–mortality if this complication arises.

TLB is contraindicated in the presence of bleeding abnormalities. An international normalized ratio (INR) greater than 1.5 is an absolute contraindication. When oral anticoagulation therapy is taken, it should be withheld for at least four days or until INR is <1.5 [31]. Fresh-frozen plasma can be administered to reverse oral anticoagulant therapy more quickly. TLB is also contraindicated if the platelet count is less than 50,000/ μL. The platelet count can improve quickly with platelet transfusions prior to the procedure. There are insuf cient data on antiplatelet agents such as clopidogrel, but some bronchoscopists require withholding treatment with this agent at least 1 week before the procedure. Finally, arterial pulmonary hypertension, which is quite usual in advanced stages of some brotic ILDs, may increase the risk of fatal bleeding.

Functional respiratory test and oxygen saturation should be evaluated prior to TLB or TLB-C, since it is not recommended in severe hypoxemia (PaO2 < 55 mmHg), DLCO < 35%, or FVC < 50% [3, 42]. There are some contraindications inherent to beroptic endoscopic procedures that of course also apply, such as uncontrolled cardiac arrhythmias, unstable angina, or high intracranial pressure. There is little information about TLB performed in patients on mechanical ventilation, but it is known that there is a higher risk for pneumothorax [31].

Future Directions

The pathogenesis of different ILDs has been better understood thanks to continuous research on transbronchial samples [48–56]. Recently, it has been known that gene and protein expression patterns could identify key molecules involved in different ILDs [48–56]. These speci c proteinndings could provide relevant information for clinical diagnosis of ILDs and targets for effective therapies. Protein synthesis is determined by genetic and metabolic factors that may be the clue to some ILD development. Different technologies such as DNA and protein microarrays are useful to identify gene and protein expression patterns. The improvement in the world of genomic–proteomic approach may increase the utility of BAL for ILD diagnosis and management, monitoring disease activity, and assessing the effect of therapeutic interventions [54]. Recent investigations based on protein pro le examination in BAL have demonstrated differences between IPF and other brotic lung diseases such as HP or brosis associated with connective tissue disease or other ILDs such as sarcoidosis [52–56]. More recently, the BRAVE clinical trials with Envisia genomic classi er have demonstrated to identify the UIP pattern from lung samples obtained through conventional means and from cryobiopsy transbronchial lung samples [57, 58]. Therefore, the future clinical use of arrays that will help in identifying the histological pattern could increase the requirement of transbronchial lung samples.

Summary andRecommendations

The number of recognizable cyto-histopathologic reaction patterns in ILDs is limited, and their morphological speci city in the diagnosis of ILDs is variable.

BAL should be considered in all patients with suspected infection, malignancy, and some ILDs in which it may be diagnostic. The utility of BAL in ILD diagnosis depends on different factors: expertise obtaining, analyzing, and interpreting the results are the main ones. When diagnosis is

uncertain after clinical assessment and HRCT scanning, typical BAL cellular pro les may provide important clues in some ILDs such as sarcoidosis or HP. However, BAL is not a diagnostic tool in patients with clinical features and HRCT pattern typical of IPF (consistent UIP pattern). In this situation, BAL mainly helps to support other entities with similar presentation, such as HP or NSIP, and it is only recommended in a clinical context not appropriate for IPF.

Some biopsy specimens may provide speci c clues that are diagnostic of the underlying disease, whereas others reveal only non-speci c abnormalities. TLB-C is a powerful tool for diagnosis of speci c ILD when matched with appropriate expectations on the part of clinicians, radiologists, and pathologists, and may avoid the need of SLB.

HRCT images are essential for choosing the best place to biopsy and to help in the nal diagnosis. TLB is the initial procedure of choice in those patients in whom small samples may be diagnostic, particularly if the disease has a tendency for broncho-centric involvement, and, when possible, BAL and TLB should be performed before the initiation of any treatment. Conventional TLB is not recommended in IPF or other ILDs with UIP radiological pattern; however, TLB-C may be useful for diagnostic yield of the MDD in these cases.

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