Advances in pediatric flexible bronchoscopy

Clinical application of bronchoscopy originated in 1897 with Killian’s successful extraction of a pork bone from the right main bronchus [7]. Flexible fiberoptic bronchoscopy was conceived later by Shigeto Ikeda in 1967; it was initially limited to use in adults [8]. Pediatric fiberoptic bronchoscopy was pioneered by Drs. Robert Wood and Robert Fink in 1978 [9]. However, it lacked a working channel and primarily served the purpose of visual examination [9]. A significant advance occurred in 1980 with the introduction of a prototype flexible bronchoscope featuring a 3.5 mm outer diameter and a 1.2 mm working channel, which highlighted fundamental therapeutic capabilities (e.g., BAL) for pediatric patients across all age groups [10]. Since 2000, electronic bronchoscopes (e.g., Olympus BF-P260F) have gradually replaced traditional fiberoptic scopes, offering high-definition imaging, video recording functionalities, and a safer operational experience. In 2002, the introduction of the Olympus BF260 series of flexible bronchoscopes, known as “hybrid-type” bronchoscopes, incorporated standard fiberoptic equipment with newer video chip technology. This allowed for smaller outer diameters, larger working channels, and improved visual resolution [6]. With an outer diameter of 4.0 mm and a working channel of 2.0 mm, the “slim” Olympus BF-P260F bronchoscope provided pediatric pulmonologists with superior suction capability and broadened access to instruments that were previously exclusive to their adult counterparts. This included protected cytology brushes, standard biopsy forceps, and foreign body retrieval baskets [6]. In 2004, the “ultraslim” Olympus BF-XP260F bronchoscope, featuring a 2.8 mm outer diameter and a 1.2 mm working channel, enabled diagnostic and therapeutic procedures to be performed in small, premature infants [6].

Evolution of bronchoscopy from the early limitations of rigid scopes to the revolutionary adoption of fiberoptic technology, and now to state-of-the-art miniaturization of electronic scopes, spans more than 100 years [11]. This evolution in size reduction runs alongside advances in anesthetic techniques, the establishment of standardized procedural protocols, and the fostering of multidisciplinary collaboration [11].

The decision to pursue PFB for diagnostic and/or therapeutic purposes is invariably based on a careful assessment of each individual case, taking into account medical history of the patient, physical examination, and results from previous diagnostic evaluations. Indications for PFB are summarized in Table 1 [2‐5]. In recent years, substantial progress in the application of innovative tools designed for endobronchial procedures and image-guided tissue sampling has drastically expanded the scope of PFB. Indeed, this has led to the introduction of two new concepts: advanced diagnostic bronchoscopy and interventional bronchoscopy [12‐14]. Specifically, advanced diagnostic bronchoscopy has encompassed an array of sophisticated techniques, notably endobronchial ultrasound (EBUS)-guided transbronchial lung and lymph node biopsy, computed tomography (CT) navigation, and use of robotic technology [14]. Advanced interventional bronchoscopy refers to therapeutic procedures that include laser ablation, cryotherapy, electrocautery, argon plasma coagulation, tissue debulking, balloon dilation, stent placement, injection, and foreign body removal [14]. Applications of advanced diagnostic and interventional bronchoscopy are outlined in Table 2 [12‐14].

Contraindications for PFB are primarily influenced by operator skill and equipment availability. Relative contraindications for PFB include severe cardiopulmonary dysfunction, life-threatening arrhythmias (e.g., atrial fibrillation, ventricular fibrillation, flutter, and third-degree atrioventricular block), advanced pulmonary hypertension, hyperpyrexia, active/impending massive hemoptysis, significant bleeding disorders, severe malnutrition, and an inability to tolerate surgical interventions [2‐5]. Even when faced with challenges such as cardiovascular instability, pulmonary hypertension, coagulopathy, severe hypoxemia or respiratory failure, appropriate measures can be implemented for the safe use of PFB where this is considered necessary [2‐5]. Ultimately, both benefits and risks should be individually assessed. We consider it prudent to avoid PFB when the risks outweigh the potential benefits.

The key points of preoperative preparation for PFB are listed in Table 3 [4, 5, 15]. A thorough preoperative evaluation (e.g., disease severity, optimal timing for surgery, anesthetic protocol, and emergency response plan) prior to PFB is crucial to guarantee successful execution of the procedure and reduce the risk of complications.

Selection of an appropriate anesthetic is crucial for the smooth implementation of PFB. This is influenced by several clinical factors, including disease characteristics, nature and demands of the procedure, patient safety and comfort, availability of requisite equipment and skilled professionals, and adequate conditions for therapeutic or diagnostic PFB. The most commonly employed anesthetic protocols include topical, local combined with conscious sedation, and general anesthesia.

In response to a growing demand for humanistic care, local surface anesthesia is seldom used in isolation. Except in instances involving children where it is crucial to monitor the dynamic airway characteristics of the airway, a combination of local surface anesthesia and conscious sedation or general anesthesia is generally preferred in the majority of cases.

The anesthetic technique of “local anesthesia while proceeding” coupled with conscious sedation for bronchoscopy is straightforward to implement and does not require the participation of anesthesiologists. The incidence of peri-procedure-related respiratory depression is minimal, rendering this approach ideal for brief interventions such as BAL. However, this approach may provoke adverse events such as limb movement and coughing, especially in those who experience insufficient sedation.

General anesthesia typically administered by anesthesiologists enables patients to withstand longer procedures and significantly reduces the likelihood of endoscopic complications (e.g., bleeding, injury, and pneumothorax). With the involvement of anesthesiologists, the anesthetic plan can be rapidly modified in response to changing circumstances. For instance, if a bronchial foreign body is not removed using PFB, anesthesiologists can swiftly deepen anesthesia to facilitate extraction via rigid bronchoscopy. General anesthesia markedly improves the acceptability of PFB among children and their caregivers [16, 17]. Based on different ventilatory methods, general anesthesia is classified into intravenous combined anesthesia, laryngeal mask airway anesthesia, and tracheal intubation anesthesia (Table 4).

BAL is a versatile tool for the diagnosis, prognosis evaluation, and clinical treatment of various respiratory diseases. These include pulmonary infections, hypersensitivity pneumonia, asthma, diffuse lung disease, as well as opportunistic infections in immunocompromised patients [18]. For most clinical applications, the flexible bronchoscope is gently wedged into the target bronchus, and normal saline at 37 °C is sequentially instilled through the working channel of the bronchoscope. The recommended volume for BAL in pediatric patients is 1 mL/kg per aliquot, with a maximum of 20 mL for each aliquot. The total lavage volume should not exceed 5–10 mL/kg, to be administered in 3–4 consecutive aliquots. BAL fluid (BALF) is gently recovered using a suction device with a selected negative pressure to avoid airway collapse; the minimal total volume retrieved is recommended to be ≥ 40% of the instilled volume [4, 19].

Although the cellular composition of BALF in healthy individuals varies in different studies [4, 19, 20], both domestic and international guidelines describe the proportion of cells in BALF as follows: lymphocytes 10%–15%, neutrophils ≤ 3%, eosinophils ≤ 1%, and alveolar macrophages (Am) > 85% [5, 21]. Atypical shifts in the ratios of cellular components in BALF provide critical insights in the diagnosis of pulmonary disorders [4, 21, 22] (Table 5). Moreover, BALF is more suitable than sputum for the detection of specific microbiological infections, as this tends to be less contaminated by oral bacteria during collection [23]. Identification of pathogens in BALF provides critical information on respiratory tract infection and enables both precise antibiotic therapy and assists in prognostic assessment [24, 25]. In addition, BAL serves as a potent therapeutic intervention for the removal of pathogenic agents (e.g., lipids [26], proteinaceous substances [27], and mucus [28, 29]) and inflammatory mediators from the alveoli in a spectrum of pediatric pulmonary disorders (e.g., exogenous lipid pneumonia [26], pulmonary alveolar proteinosis [27], and refractory pneumonia [28, 29]). Collectively, this can mitigate inflammatory responses, enhance pulmonary ventilation, alleviate clinical symptoms, and improve prognosis.

Mediastinal lymphadenopathy poses a considerable clinical challenge in pediatric patients; however, the emergence of transbronchial needle aspiration (TBNA) improves the diagnostic efficacy of FB (Table 6). The youngest patient documented to have undergone conventional TBNA (c-TBNA) with a flexible bronchoscope was only 9 months old [30]. Although c-TBNA is safer than classic endoscopic techniques (e.g., mediastinoscopy, video-assisted thoracoscopic surgery, and thoracotomy), it is a “blind” procedure that is restricted to sampling larger subcarinal/right paratracheal lymph nodes. EUBS-TBNA which typically employs linear probe ultrasound for real-time TBNA presents a minimally invasive and safe alternative. In institutions with experienced bronchoscopy and anesthesia teams, EBUS-TBNA can be employed for sampling mediastinal or hilar lesions and diagnosis of a variety of conditions, such as leukemia, lymphoma, sarcoidosis, tuberculosis, and other infections [31‐33]. Current literature reveals that the youngest patient to receive EBUS-TBNA was 6 years old, using an Olympus BF-UC160F with a 6.9 mm outer diameter [34]. Therefore, EBUS-TBNA with a 6.3 mm outer diameter (such as the Fujifilm EB-530US or the Olympus BF-UC290F) could theoretically be considered for even younger patients.

Since the diameter of available EBUS scopes (usually 6.9–7.4 mm) exceeds those of conventionally used pediatric flexible bronchoscopes (typically 2.8–4.2 mm), performing EBUS-TBNA poses challenges in younger children with smaller tracheas [35]. As a viable alternative, endoscopic ultrasound with bronchoscope-guided fine needle aspiration (EUS-B-FNA) [36] has gained support for its ability to assess lesions that are inaccessible via the airway and serves as the exclusive approach for small children. The youngest reported age for the application of EUS-B-FNA is currently 20 months [37].

When choosing between EBUS-TBNA and EUS-B-FNA, several factors should be considered; these include: lymph node location, patient age, and airway diameter [31]. When both methods are feasible for target lymph node access, the decision should harmonize patient-specific situations and operator proficiency to guarantee a safe and effective diagnostic outcome [38].

Radial probe EBUS (rpEBUS) employs a flexible catheter housing a rotating ultrasound transducer that generates a comprehensive 360° “radial” ultrasound image [39]. Direct contact rpEBUS probes, featuring outer diameters of 1.7 to 2.5 mm, are capable of delivering high-resolution images at frequencies between 12 and 30 MHz and can be advanced through the working channel of a pediatric-size bronchoscope for the identification and assessment of peripheral lung lesions [40]. Bouso et al. were pioneers in the application of rpEBUS-guided transbronchial biopsy in children where they showcased its practicality, safety, and increased diagnostic tissue yield in immunocompromised children with chest radiographic opacities [41].

Despite the widespread application of c-TBNA, EBUS-TBNA, EUS-B-FNA, and rpEBUS in adults, there exists a dearth of literature regarding use and efficacy in pediatric populations [31, 38‐41]. While collaboration with adult pulmonologists offers numerous opportunities for the evolving discipline of pediatric interventional pulmonology (such as improved transfer of skills and expertise), it is essential to acknowledge the considerable disparities in disease patterns, anatomical factors, and treatment methodologies between adult and pediatric populations. To ensure the field flourishes, there is a pressing need to strengthen awareness of, and training, pediatric interventional bronchoscopy through global cooperation and the development of educational courses [42].

Common complications associated with PFB include anesthetic drug allergies, decreased blood oxygen saturation or hypoxia, asphyxia, arrhythmia, laryngospasm or bronchospasm, epistaxis, hemoptysis, infection, fever, pneumothorax, as well as mediastinal and subcutaneous emphysema [4, 5]. The most common causes of complications stem from inadequate bronchoscopic technique and lack of experience [73], insufficient preoperative evaluation (comorbidities) [74, 75], selection of an inappropriate bronchoscope model for the patient’s needs, improper anesthetic sedation, insufficient piped oxygen supply, ineffective infection control, inadequate perioperative nebulized medication therapy, and difficulties in establishing effective intravenous access. Life-threatening adverse events primarily arise from anesthetic drug overdose, inadequate monitoring, and inadequate sedation. Major risk factors include upper airway pathology, persistent radiographic abnormalities, oxygen dependency, and body weight < 10 kg [76]. Desaturation is the most frequent complication during the procedure, closely followed by epistaxis. Cough is the most prevalent post-bronchoscopy complication, succeeded by fever [77, 78].

The key to minimizing complications in PFB lies in comprehensive preoperative evaluation and preparation, standardized intraoperative procedures with real-time monitoring, close postoperative observation and timely intervention, along with multidisciplinary teamwork and well-equipped facilities [5]. Throughout the procedure, it is vital to continuously monitor vital signs to ensure the oxygen saturation exceeds 95%. If this dips below 85% in conjunction with an abnormal heart rate, the procedure should be immediately halted and appropriate intervention initiated. Continuous postoperative monitoring for at least 2 hours is required to intervene where dyspnea, hemoptysis, and fever occur. Owing to the influence of anesthesia, children are advised to abstain from food and drink for a minimum of 2-hour post-procedure. For complex cases, multidisciplinary cooperation and personalized treatment strategies play a crucial role in reducing complications and improving therapeutic outcomes [72, 79‐81].

PFB has evolved beyond a purely diagnostic tool to become an indispensable procedure in modern pediatric respiratory medicine. Its practical relevance is undeniable, offering minimally invasive access for the identification of intricate airway anomalies, infectious etiologies, and FBA aspiration, while increasingly enabling crucial therapeutic interventions. The ability to perform PFB under conscious sedation in a wide range of pediatric patients further emphasizes its practical application and patient-friendly characteristics, allowing dynamic assessment and targeted sampling. Nevertheless, there are challenges that require focus. These include optimizing procedural protocols and ensuring safety for the youngest and most critically ill patients. Moreover, improving diagnostic yields for elusive conditions through advanced ancillary techniques, establishing robust standardized training and credentialing pathways globally to guarantee consistent quality and safety, and tackling resource disparities that restrict access are additional challenges. Future endeavors should be concentrated on: (1) advancing technological innovation to develop smaller, higher resolution scopes and more sensitive point-of-care diagnostic tools; (2) implementing and evaluating structured, competency-based training programs to bridge the training gap; (3) fostering collaborative, multi-center research to yield robust pediatric-specific evidence concerning outcomes, techniques, and novel applications; and (4) identifying and addressing barriers to equitable access to PFB expertise. Addressing these challenges and striving in this direction is imperative to unlocking the full potential of PFB, ensuring all children benefit from its diagnostic accuracy, therapeutic capabilities, and minimally invasive approach.