and left upper lobes at a third and nal treatment session [11]. All three treatments are done approximately 3 weeks apart to minimize asthma exacerbation.

Post-procedure

Patients are observed post-procedure as per local treatment protocols, experience, and routine postbronchoscopy care. Nebulized bronchodilators are administered post-procedure every 15 min on as needed basis. Based on the AIR, RISA, and AIR2 trials, the most common adverse events are severe asthma exacerbation, cough, wheezing, and respiratory tract infections [11]. Spirometry with posttreatment FEV1 < 80% compared to pre-BT FEV1 on the day of procedure warrants an admission. Chest X-ray is not typically performed post-proce- dure. Asthma exacerbation was seen most commonly within one-week post-procedure. Due to this, routine check-in is recommended with the patient at 24 h, 48 h, and at 7 days post-procedure [11]. Most importantly, post-educational material should be provided to patients and families.

Conclusion

BT is FDA-approved non-pharmacological endoscopic treatment that should be considered for severe refractory asthma that is otherwise not controlled despite maximal therapy. BT reduced exacerbations and improved quality of life while maintaining a good safety pro le that is persistent at 1, 5, and 10 years.

Acknowledgments  Boston Scienti c is acknowledged for allowing to present Figs. 36.1, 36.2, 36.3, and 36.4 in this text.

References

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3.\Wahidi MM, Kraft M. Bronchial thermoplasty for severe asthma. Am J Respir Crit Care Med. 2012;185(7):709–14.

4.\Chaudhuri R, et al. Safety and effectiveness of bronchial thermoplasty after 10 years in patients with persistent asthma (BT10+): a follow-up of three randomised controlled trials. Lancet Respir Med. 2021;9(5):457–66.

5.\d'Hooghe JNS, et al. Airway smooth muscle reduction after bronchial thermoplasty in severe asthma correlates with FEV1. Clin Exp Allergy. 2019;49(4):541–4.

6.\Pretolani M, et al. Effectiveness of bronchial thermoplasty in patients with severe refractory asthma: clinical and histopathologic correlations. J Allergy Clin Immunol. 2017;139(4):1176–85.

7.\Langton D, et al. Bronchial thermoplasty increases airway volume measured by functional respiratory imaging. Respir Res. 2019;20(1):157.

8.\Konietzke P, et al. Quantitative CT detects changes in airway dimensions and air-trapping after bronchial thermoplasty for severe asthma. Eur J Radiol. 2018;107:33–8.

9.\Haj Salem I, et al. Persistent reduction of mucin production after bronchial thermoplasty in severe asthma. Am J Respir Crit Care Med. 2019;199(4):536–8.

10.\Cox G, et al. Asthma control during the year after bronchial thermoplasty. N Engl J Med. 2007;356(13):1327–37.

11.\Tan LD, et al. Bronchial thermoplasty: a decade of experience: state of the art. J Allergy Clin Immunol Pract. 2019;7(1):71–80.

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Introduction

Interstitial lung diseases (ILDs) involve a group of respiratory entities in which the main pathological alteration affects the interstitial alveolar structures, but also can affect the small airways and the pulmonary vasculature [1]. Clinical, radiologic, and lung function presentations may be common in several ILDs [1]. Cytological evaluation and/or histological study are usually crucial to achieve the con dent diagnosis and to rule out other causes of interstitial lung pathology such as infections or cancer [1]. Surgical lung biopsy (SLB) may be too risky in some cases given the clinical, lung function, or cardiovascular status and it is performed in only 20–40% of patients [2]. Therefore, bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial lung biopsy (TLB) is often the initial procedure [2–4]. BAL and TLB, specially the transbronchial lung cryobiopsy (TLB-C), may provide suf-cient evidence to diagnose sarcoidosis, amyloidosis, hypersensitivity pneumonitis (HP), eosinophilic pneumonias, organizing pneumonia, pulmonary Langerhans cell disease (histiocytosis X), Goodpasture’s syndrome, lymphocytic interstitial pneumonia, some pneumoconiosis, pulmonary lymphangioleiomyomatosis, and pulmonary

A. Gruss · M. Molina-Molina (*)

ILD Unit, Respiratory Department, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain

alveolar proteinosis (PAP), as well as infections and neoplastic processes presenting with interstitial lung in ltrates [3, 4]. The introduction of TLB-C achieves better preserved and bigger histological samples, allowing the identi cation of the whole spectrum of histological patterns. Therefore, this new tool increases the diagnostic yield of bronchoscopy in ILDs. When clinical information and high-resolution computed tomography (HRCT) ndings are combined with BAL fuid analysis and TLB-C, a con dent diagnosis frequently emerges that obviates the need for SLB [4]. However, some considerations should be made to take advantage of both procedures in ILD evaluation.

Bronchoalveolar Lavage (BAL)

BAL has gained wide acceptance as a safe method to obtain respiratory secretions for the examination of cellular and acellular components for both diagnostic and research purposes [5, 6]. Certainly, much data have been published over the past decades that demonstrate the utility of BAL to identify agents of respiratory infections and changes in the composition of the airspace environment associated with the presence of non-­ infectious parenchymal lung diseases. The introduction of HRCT at the end of the last century represented a revolutionary improvement in the diagnosis of speci c forms of ILD and a useful

tool to decide the best place to obtain respiratory samples [6]. BAL is now routinely used as a tool to diagnose respiratory infections, study diffuse parenchymal lung diseases, and monitor the status of transplanted lung allografts [7]. Despite the widespread use of BAL by pulmonologists, BAL cellular analysis, especially nucleated immune cell differential counts, may be underused in ILD diagnosis since its results differ from center to center and depends on multiple factors [8, 9]. BAL appearance and differential cell count should be interpreted appropriately and evaluated with an updated awareness of the potential diagnoses associated with each cellular pattern to provide useful diagnostic clues [7–9].

Technical Aspects of BAL Procedure

The usefulness of the BAL in ILD is only possible if: (a) the bronchoscopist uses an appropriate technique to obtain the fuid; (b) the differential cell count is performed according to good clinical laboratory practice, by experienced personnel; and (c) cell count and evaluation is interpreted by an expert pathologist in ILDs [6–8].

BAL technique through the beroptic bronchoscope is not dif cult to perform but it could reach best results if certain advice is followed [10–12]. To retrieve alveolar cells or cells from distal airspaces, enough isotonic saline should be instilled [12]. Proximal large airway secretion contamination should be avoided by maintaining the distal end of the bronchoscope in a wedged position in a segmental or subsegmental bronchus throughout the period required for the instillation and retrieval of saline aliquots [12]. Furthermore, aliquots should be aspirated immediately once the entire aliquot volume has been instilled. Many different BAL protocols have been published and consist of multiple aliquots:ve or six aliquots of 20 mL each, three of 50 mL, or four of 60 mL [12, 13]. The rst aliquot frequently represents bronchial airway cells and secretions, so it is recommended to keep it separate and just use it for microbiological analysis. The other aliquots should be pooled and used for cellular analysis [12, 13].

The right middle lobe and lingula of the left upper lobe have traditionally been used for lavage since they are easily accessible areas and allow good return of BAL fuid [10]. However, nowadays patients with ILD are routinely evaluated with chest HRCT images that are used to target areas of the lung that may be more representative of the disease process (ground glass attenuation, prominent nodularity, or ne reticulation) and that could increase the possibility to obtain relevant information (abnormal areas located proximal and peribronchial) [6].

If possible, the percentage of BAL fuid that is retrieved should be ≥30% of the instillation for a reliable cellular analysis [13]. An accurate cell count and evaluation of BAL requires examination of at least more than 300 nucleated cells [6]. The presence of squamous epithelial cells suggests that oropharyngeal secretions have contaminated the BAL fuid. More than 5% of squamous or bronchial epithelial cells mean that the BAL sample is unsuitable for cell analysis. It is of key importance that the technicians handling the samples, analyzing the BAL slide preparations, and performing differential counts are adequately trained in proper identi cation of BAL cells [6]. Afterward, expert pulmonologists in ILD, familiar with BAL cell patterns, should interpret the BAL analysis results [8, 9].

BAL fuid obtained from healthy, never-­ smoking individuals contains most alveolar macrophages (80–95%), some lymphocytes (5–12%), and very few neutrophils (<5%) or eosinophils (<1%) [4]. BAL cell count from smokers has a signi cantly increased total BAL cell amount, but the BAL differential cell count is similar than never-smokers or ex-smokers, except for a lower percentage of lymphocytes [4, 14]. Age can modify the total and differential BAL cell account. It seems that elderly subjects present more lymphocytes and neutrophils in their differential cell count, and that the volume of retrieved fuid declines with advanced age [15]. Regarding the total volume instilled of saline solution, a range from 100 to 250 mL appears to give similar cell differentials in individual patients with ILD [12]. When a bacterial infection is suspected during the study of diffuse lung in ltrates or co-exists

with non-infectious ILD, the rst non-­centrifuged aliquot of BAL should be examined for quantitative bacterial culture, including mycobacterial and fungal screening. If viral infection or intracellular bacteria (Pneumocystis jirovecii) are suspected, centrifuged BAL fuid enhances their detection through stains or viral nucleic acid probes [10].

ILD Cell Patterns and Diagnosis from BAL

A con dent BAL cell evaluation, including differential cell count and other macro or microscopic characteristics, in combination with clinical and imaging data, provides relevant information that contributes signi cantly to the diagnosis of speci c ILD (Table 37.1) [1, 5, 17– 19]. Furthermore, cytopathological examination may rule out other causes of parenchymal lung diseases with a similar radiological pattern such as malignancies (bronchoalveolar and lymphangitic carcinoma) or infection (P. jirovecii) [20]. In the appropriate clinical and radiological setting, certain gross and cellular ndings in BAL may help in the differential diagnosis for a speci c ILD. Recent data suggest that predictive value of BAL for ILD diagnosis is very useful for some entities such as sarcoidosis (frequent and predominant peribronchial disorder), in contrast to rare forms of ILD or common forms that predominantly affect subpleural space or do not associate a speci c differential cell count (such as idiopathic pulmonary brosis [IPF]) [21].

BAL macroscopic appearance is very important. Retrieved BAL fuid that has milky or light brown appearance, with protein content that settles to the bottom of its container, clearly suggests pulmonary alveolar proteinosis (PAP) [22]. The diagnosis requires con rmation through the positive staining with Schiff periodic acid (PAS+). In this case, whole-lung lavage is still considered the treatment for PAP, although there is no scienti c evidence that supports the best protocol to perform it. On the other hand, a grossly bloody lavage fuid is suggestive of diffuse alveolar hemorrhage (DAH) when it

Table 37.1  Histopathological patterns and MDD diagnosis for specimens obtained by TLB-C and SLB

n = 65; ILD interstitial lung diseases, MDD multidisciplinary discussion, SLB surgical lung biopsy, TBL-C transbronchial lung cryobiopsy, UIP usual interstitial pneumonia

Modi ed from: “Diagnostic accuracy of transbronchial lung cryobiopsy for interstitial lung disease diagnosis (COLDICE): a prospective, comparative study.” The Lancet Respiratory Medicine 2020;8:171–181 [16]

aFor the MDD nal diagnoses, raw agreement between TBLC and SLB was 76.9% with a κ of 0.62 (0.47–0.78)

increases in the sequentially retrieved BAL fuid aliquots [21]. Furthermore, alveolar macrophages can stain positively for hemosiderin if the BAL is performed 24–48 h after the onset of hemorrhage.

BAL lymphocytosis can be found in cryptogenic organizing pneumonia (COP), cellular non-­speci c interstitial pneumonia (NSIP), hypersensitivity pneumonitis (HP), sarcoidosis,

drug toxicity, and lymphoid interstitial pneumonia (LIP) [21]. When mast cells or plasma cells are also increased, the diagnosis of HP is more probable, although mast cells can be observed in sarcoidosis, drug reactions, and ILD associated with collagen vascular disease or COP [21]. A percentage of eosinophils higher than 25% is usually associated with eosinophilic lung disease, mainly acute eosinophilic pneumonia [23]. Neutrophil’s predominance is usually due to infection or acute lung injury, although some IPF patients also present increased neutrophil count, but to a lesser degree.

Some morphological changes in alveolar macrophages are also important: cytoplasmic inclusions are suggestive of viral infection, vacuolated cytoplasm with positive staining for fat can be observed in chronic aspiration pneumonitis, asbestos bodies in asbestos disease, dust particles in other pneumoconiosis, and phagocyted red blood cells in DAH [21].

BAL differential cell count utility in a patient with ILD that presents a usual interstitial pneumonia (UIP) pattern in the thoracic HRCT is limited. It mainly helps identify other non-IPF entities that can also present the same radiological ndings. An increased lymphocyte cell count in BAL would suggest the possibility of chronic HP, brotic NSIP, or other diagnoses associated with BAL lymphocytosis [2, 3, 24, 25]. However, if clinical or epidemiological data suggest other non-IPF UIP entity, BAL could help in the differential diagnosis, and it may help to identify some chronic HP [24, 25].

Flow cytometric analysis can improve the performance of BAL in some instances, mainly when the ILD differential diagnosis includes sarcoidosis, pulmonary Langerhans cells histiocytosis, and lymphoid malignancy [1, 21, 26]. However, due to the high cost of this procedure, fow cytometry is only used for the evaluation of CD4+/CD8+ cell ratio [21].

Alterations in BAL lymphocyte subsets have been widely examined, especially for sarcoidosis [1, 27]. Conventionally, a high CD4+/CD8+ T-lymphocyte ratio associated with BAL lymphocytosis is suggestive of sarcoidosis. However, elderly subjects can also present elevated CD4+/

CD8+ ratio, so age is a variable to consider for appropriate interpretation [17]. Recent data have demonstrated that the presence of a CD4+/CD8+ ratio of ≥3.5 is relatively speci c for sarcoidosis [21, 27]. However, the sensitivity of this ratio is low since many patients do not have an elevated ratio or may even have a low one [21]. On the other hand, a decreased CD4+/CD8+ ratio has been observed in HP, drug toxicity, COP, and eosinophilic diseases [4, 21]. Therefore, the ef - cacy of this ratio is low for other ILDs different from sarcoidosis.

The diagnosis of pulmonary Langerhans cell histiocytosis can be supported by the presence of more than 4% CD1+ cells in BAL, which is more frequent in early stages of the disease [28]. These cells can be seen by means of immunohistochemistry or fow cytometry. Both techniques are also useful to identify monoclonal lymphocyte populations in the differential diagnosis of lymphoid diseases.

Finally, BAL cell analysis early in the study of an acute ILD, such as acute interstitial pneumonia, eosinophilic pneumonia, DAH, acute HP, acute COP, drug toxicity, or acute exacerbation of an underlying ILD, may help in their diagnosis [4, 21]. The study of BAL fuid can reveal infection or hemorrhage, large numbers of eosinophils (eosinophilic pneumonia), and an increase in lymphocytes (acute HP and drug toxicity) or plasma cells (acute HP). Careful consideration of the respiratory and clinical status should be evaluated before performing BAL, since worsening in those parameters is not unusual and has been reported after this procedure [3, 5].

Some centers use less amount of instillation while performing BAL in acute disease, with good results. A risk–bene t analysis is in order, in a patient-to-patient basis [3].

Transbronchial Lung Biopsy: A New

Era Introducing the Cryobiopsy

Some ILDs are associated with typical histopathologic features that can be distinctive even in small lung biopsy specimens. Whereas in most granulomatous pneumonias conventional trans-

bronchial biopsies with forceps may be enough to achieve a con dent diagnosis, for many other ILDs only the possibility of bigger and better transbronchial samples using cryoprobes has brought new possibilities for the diagnostic yield of bronchoscopy.

The main utility of the TLB-C in ILD is based on the possibility of making a speci c diagnosis, which avoids the need of an SLB in several cases. Bronchoscopy can be done as an outpatient procedure, usually with minimal morbidity and mortality [29, 30]. A new tool for obtaining samples through beroptic bronchoscopy was developed at the beginning of this century: the cryoprobe. It is a device with a distal fast frozen probe that removes tissue samples. This new technique was initially used for the diagnosis of lung cancer, but during the last decades, it has been found to be a safe method to study diffuse lung diseases (Fig. 37.1).

Classically, conventional TLB by forceps has been an appropriate rst biopsy procedure in patients with broncho-centric ILD, especially sarcoidosis, lymphangitis, organizing pneumonia, hemosiderosis, and infection [31–35]. Currently, with the introduction of cryoprobes

and the progressive improvement in the procedure of TLB-C, with better samples and protocols to decrease the incidence of adverse events (bleeding and pneumothorax), almost all ILDs can be diagnosed in the appropriate multidisciplinary expert approach [16, 36–43].

The ef cacy of TLB in the diagnosis of ILD depends in part on the differential diagnosis that is done after careful evaluation of clinical and radiological ndings [31–35]. UIP cannot be accurately diagnosed by conventional TLB, since its histological pattern cannot be determined by this technique due to two main reasons: (a) the “subpleural” space is quite impossible to be evaluated, and (b) the size of the tissue sample obtained with forceps is not enough to appreciate all the changes required to de ne this condition [31, 36]. However, Tomasseti et al. described the possibility of nding a UIP pattern through TLB-C [16, 41], and many other groups further validated this observation. With cryoprobes, subpleural lung samples may be obtained in which UIP histological criteria could be achieved, which represented a change in the diagnostic approach of brotic and nonbrotic ILDs [16].