Cryotherapy via Flexible Bronchoscopy for Pediatric Plastic Bronchitis: A Case Report

Introduction

Plastic bronchitis (PB), also known as cast bronchitis, is a rare pulmonary condition, characterized by the formation of endogenous, “jelly-like”, or rigid casts within the bronchial tubes due to various underlying causes. This leads to airway obstruction, impaired ventilation, and disrupted gas exchange, with dyspnea, wheezing, chest pain, and fever as primary clinical signs [1]. In severe cases, PB can progress to life-threatening respiratory and circulatory failures.

PB is most commonly reported in children and can be associated with pediatric cardiothoracic surgeries such as Fontan procedures, infections, inflammatory processes, acute chest syndrome, or iatrogenic conditions. Viral infections, particularly influenza and adenovirus, are common causes in children. Diagnosis is typically achieved through bronchoscopy, which allows for direct visualization and removal of the casts. Histopathological examination of the cast material and bronchoalveolar lavage fluid cultures can provide insights into the underlying infection and inflammation. Management involves identifying and addressing the underlying cause and may include pharmacological treatments such as corticosteroids and mucolytics. Bronchoscopic procedures, including cryoextraction, have been effective in treating PB [2].

Since the 1970s, bronchoscopic cryotherapy has been a key treatment in endotracheal therapy, gaining popularity due to its operational convenience, safety, and efficacy [3,4].

The cryoextraction procedure includes:

Similar case reports are relatively rare. Table 1 summarizes the literature we found from the past 5 years [6–11]. Our study presents a case report on using flexible bronchoscopic cryotherapy to remove plastic casts, aiming to evaluate the effectiveness of this treatment in children with PB.

Case Report

A 4-year-old female patient was admitted due to a 4-day history of cough. She had a previous episode of cough and wheezing. The patient initially presented with cough, wheezing, and progressively worsening dyspnea at home but no fever. She was treated at our hospital’s outpatient department with intravenous piperacillin-tazobactam and methylprednisolone for 3 days, along with nebulized therapy. Although her cough decreased and wheezing improved, a follow-up chest computed tomography (CT) showed minimal improvement in pneumonia, leading to her admission for further inpatient treatment. On admission, her physical examination revealed a temperature of 37.1°C, pulse rate of 118 beats per minute, respiratory rate of 28 breaths per minute, blood pressure of 110/67 mmHg, and oxygen saturation of 98%. She had coarse breath sounds in both lungs with a few coarse crackles but no wheezing. Laboratory tests showed a white blood cell count of 11.51×109/L, neutrophil percentage of 62.7%, hemoglobin of 125 g/L, platelet count of 330×109/L, and high sensitivity C-reactive protein (CRP) of 0.67 mg/L. Imaging studies included a chest X-ray indicating left lower lobe pneumonia with a small amount of pleural effusion on the left side, and a chest CT scan with airway reconstruction showing left lower lobe pneumonia with atelectasis and non-patent bronchi within the affected area, along with a small amount of left pleural effusion (Figure 1).

On the second day of admission, the child underwent bronchoscopy and cryoextraction. During the procedure, the left main bronchus and the openings of the left upper lobe branches were found to be patent, while the left lower lobe bronchus and its branches were obstructed by casts. Multiple attempts were made to remove the casts (Figure 2). Initial attempts to remove the foreign body using a basket and biopsy forceps were unsuccessful. Ultimately, cryotherapy was employed to successfully extract the endogenous foreign body. The EVIS LUCERA BF-P260F electronic bronchoscope, sourced from Olympus Corporation (Tokyo, Japan), has an external diameter of 4.0 mm and a working channel diameter of 2.0 mm. The cryotherapy system utilized in the procedure was supplied by ERBE Elektromedizin GmbH (Tuebingen, Germany), with the cryoprobe having an external diameter of 1.9 mm. The cryoprobe was meticulously applied to the surface of the plastic sputum plug. After a 10-s freezing period, the plug and the cryoprobe were successfully extracted. Finally, several casts were extracted, with the longest one measuring approximately 6 cm (Figure 3). The airways were then lavaged with normal saline, flushing out mucus plug-like fluid. All airway lumens were found to be patent after bronchoscopy.

Meanwhile, the child was also receiving intravenous piperacillin-tazobactam and nebulized therapy. After the first bronchoscopy, the child’s cough symptoms significantly improved starting from the third day and gradually resolved thereafter. A chest X-ray on the sixth day showed significant resolution of the pneumonia. Bronchoscopy on the seventh day revealed patency of the previously obstructed bronchial lumen, leading to the patient’s discharge on the eighth day.

After 2 months of follow-up, the child’s pulmonary imaging had essentially returned to normal.

Discussion

This case report of a 4-year-old girl with a 4-day history of cough and progressive dyspnea, diagnosed with left lower lobe pneumonia and pleural effusion, highlights several important lessons. Initial treatment with piperacillin/tazobactam and methylprednisolone, along with nebulization, provided symptomatic relief but did not resolve the underlying airway obstruction. The persistence of pneumonia and bronchial obstruction on follow-up imaging underscored the need for further intervention.

The successful removal of multiple bronchial casts via flexible bronchoscopy and cryoextraction on the second day of hospitalization was critical in alleviating the patient’s symptoms. This approach has been shown to be effective in managing airway obstruction caused by bronchial casts. The significant resolution of pneumonia on subsequent imaging and the eventual discharge of the patient highlight the importance of early and targeted intervention in such cases.

Moreover, the follow-up imaging after 2 months showing normalization of pulmonary findings underscores the potential for complete recovery with appropriate management. This case underscores the importance of considering PB in the differential diagnosis of pediatric pneumonia with airway obstruction and the utility of cryoextraction as a safe and effective treatment option.

Based on the initial imaging and laboratory test results for the child, a definitive diagnosis of PB could not be made. At that time, the diagnosis considered acute pneumonia with left lower lobe atelectasis, with viruses or atypical pathogens being the primary considerations for the etiology. Of course, we also performed differential diagnosis, taking into account the possibility of other diseases, such as bronchial foreign bodies, bronchial tuberculosis, bronchial tumors, and so on. In this case, the child was 4 years old, which is not the peak age for bronchial foreign bodies, and the parents denied any history of foreign body aspiration; therefore, bronchial foreign bodies were not considered as the primary diagnosis. Secondly, the child had an acute onset of illness with a relatively short duration, denied any history of contact with tuberculosis, and had received the Bacillus of Calmette and Guerin (BCG) vaccination. Therefore, bronchial tuberculosis was also not considered. Thirdly, bronchial tumors in children are relatively rare and were not considered as the primary diagnosis. In summary, we considered that the the most likely diagnosis was PB caused by infection with a pathogen other than Mycobacterium tuberculosis. The diagnosis was clarified on the second day after the bronchoscopy, revealing that the child had pneumonia and atelectasis caused by PB.

PB is categorized into 2 distinct types: Type I, typically associated with infection, and Type II, commonly related to congenital heart disease (CHD) [12]. Diagnosing PB is challenging due to its variable clinical presentation and the potential for misdiagnosis. In this case, the initial symptoms were nonspecific. The lack of fever and typical signs, such as stridor or hoarseness, further complicated the diagnostic process. Owing to limited diagnostic resources, a pathological examination was not conducted for this patient. However, given the absence of a history of CHD and the lack of a definitive association with a specific pathogen, the clinical presentation, including coughing, wheezing, lung infection detected through the CT scan, and the subsequent disease prognosis, indicated a Type I classification. After undergoing symptomatic and supportive treatment, along with 2 tracheal intubation procedures, the child was discharged from the hospital in a state of recovery. These factors collectively led us to classify the PB status of the patient as Type I.

The standard bronchoscopic approaches for managing PB typically encompass: 1. direct aspiration; 2. use of foreign body forceps; 3. employment of a foreign body basket; and 4. bronchoscopic brushing. In this case, initial attempts with these conventional methods yielded limited success. Given the successful application of cryotherapy in removing exogenous foreign bodies and the experience of our center in effectively extracting pseudomembranous necrotic material using a cryoprobe, we considered it prudent to explore cryotherapy as a viable treatment option. In this case, the plastic sputum plug was highly susceptible to fragmentation when removal was attempted using forceps or a retrieval basket. Additionally, the high water content of the sputum plug rendered it prone to rapid freezing. Under these circumstances, employing a small cryoprobe to freeze and remove the sputum plug proved to be a more effective approach. Consequently, bronchoscopic cryotherapy was used to extract the plastic sputum cast, culminating in the removal of a 6 cm-long cast. The primary challenges in using the foreign body basket and forceps were twofold: (1) the substantial size of the plastic sputum cast, which left a 6-cm residual segment after partial removal by the basket and forceps, and (2) the fragile nature of the plastic sputum cast, which caused it to break during extraction attempts with the basket and forceps, resulting in the removal of only small fragments each time. Ultimately, bronchoscopic cryotherapy was selected as the treatment of choice, yielding satisfactory outcomes.

Bronchoscopic interventional therapy plays a key role in managing pediatric respiratory diseases. Techniques such as endoscopic balloon dilation, tumor resection, laser therapy, and cryotherapy are increasingly adopted in pediatric practice [13]. Cryotherapy uses compressed gases – either nitrous oxide or carbon dioxide – directed through a specialized catheter or cryoprobe, enabling the metal tip to reach temperatures near −89°C rapidly. Upon contact with the tip of the probe, the liquid components of clots, secretions, or tissues freeze, forming frozen adhesions within seconds. The cryoprobe can be guided to the target area via the side port of a flexible or rigid bronchoscope. Operators can modulate the cryogenic effect by adjusting the size of the probe, contact point, and duration of contact. The development of cryoprobes as small as 1.1 mm expands their applicability across all pediatric age groups, opening new frontiers in interventional pediatric respiratory endoscopy.

Numerous successful attempts at cryopreserving foreign bodies have been made. Common foreign bodies, such as kernels and irregularly shaped objects, can typically be removed using standard forceps. However, for unique foreign bodies, including endogenous materials and pen caps, bronchoscopic cryotherapy enhances the success rate of single-session removal and considerably reduces treatment duration. Zhang et al report that cryotherapy effectively removes foreign bodies in 8 out of 12 children without complications [14]. Additionally, David et al successfully extracted a pin using a cryoprobe [15]. Han et al report that between 2018 and 2021, their center removed 633 foreign bodies, using cryotherapy in 62 cases of lung foreign bodies, nearly accounting for 10% of these cases [16]. Li and Sun removed a live leech, a foreign body, using a cryoprobe [11].

In pediatric cases, endogenous foreign bodies are also frequently encountered, such as PB, necrotic tissue, and blood clots. Kallam et al report successful removal of plasticated phlegm casts in 2 patients using cryotherapy, effectively alleviating the patients’ airway obstruction symptoms [17]. Gatt et al also successfully employed cryotherapy to remove bloody, plastic-shaped sputum casts [8]. Our center similarly utilized a cryoprobe to remove pseudomembrane necrosis, which tends to fragment when extracted with forceps [4]. Freezing with a small cryoprobe offers a distinct advantage in such instances. The present case is the first published instance of cryopneumatic sputum embolus treatment in our center and, to our knowledge, in China, offering a novel approach to managing PB via bronchoscopic cryopneumatic techniques.

We searched for similar case reports in the past 5 years, and the summary is in Table 1. When dealing with foreign bodies or endogenous foreign bodies that are prone to fragmentation, cryotherapy often enables complete removal of the foreign substances in a shorter time, as compared with forceps and basket.

The literature reports several complications associated with bronchoscopic cryotherapy, including pneumothorax, mediastinal emphysema, subcutaneous emphysema, hemorrhage, and hypoxemia, with pneumothorax and hemorrhage being the most commonly reported [18–22]. Generally, tissues with higher water content – such as granulation tissue, mucous membranes, and skin – are less resistant to freezing, whereas tissues with lower water content, such as fat, bone, and fibrous connective tissue, are more resistant. The trachea and bronchi, composed of mucosa, submucosa, cartilage rings, and connective tissue, possess a histological profile that provides a high tolerance to cryotherapy. Consequently, complications such as scar stenosis, osteomalacia, and perforation are rare occurrences in these airway structures. Although large-scale pediatric studies are limited [18,23], bronchoscopic cryotherapy has been affirmed for its high safety profile in extensive adult studies [19,24]. The operating physician must conduct a thorough preoperative assessment and proficiently control the temperature and duration of cryotherapy to minimize the risk of complications.

Conclusions

This case highlights the feasibility of bronchoscopic cryotherapy as a therapeutic option for PB and provides valuable insights for future treatment strategies. Currently, the number of reports on the use of cryotherapy in pediatric patients remains limited, with significant gaps in various aspects. Further studies are essential to evaluate its efficacy and safety in children. Bronchoscopic cryotherapy serves as a valuable diagnostic and therapeutic tool, particularly when traditional methods such as forceps and baskets are ineffective. No standardized guidelines exist for managing PB with flexible bronchoscopic cryotherapy. Additional clinical experiences are needed to inform the development of evidence-based protocols.