Customization of stent design for treating malignant airway stenosis with the aid of three-dimensional printing

Perspectives on lung visualization: Three-dimensional anatomical modeling of computed and micro-computed tomographic data in comparative evolutionary morphology and medicine with applications for COVID-19

The vertebrate respiratory system is challenging to study. The complex relationship between the lungs and adjacent tissues, the vast structural diversity of the respiratory system both within individuals and between taxa, its mobility (or immobility) and distensibility, and the difficulty of quantifying and visualizing functionally important internal negative spaces have all impeded descriptive, functional, and comparative research. As a result, there is a relative paucity of three-dimensional anatomical information on this organ system in all vertebrate groups (including humans) relative to other regions of the body. We present some of the challenges associated with evaluating and visualizing the vertebrate respiratory system using computed and micro-computed tomography and its subsequent digital segmentation. We discuss common mistakes to avoid when imaging deceased and live specimens and various methods for merging manual and threshold-based segmentation approaches to visualize pulmonary tissues across a broad range of vertebrate taxa, with a particular focus on sauropsids (reptiles and birds). We also address some of the recent work in comparative evolutionary morphology and medicine that have used these techniques to visualize respiratory tissues. Finally, we provide a clinical study on COVID-19 in humans in which we apply modeling methods to visualize and quantify pulmonary infection in the lungs of human patients.

Lesion-Adaptative Bionic Tracheal Stent with Local Paclitaxel Release for Enhanced Therapy of Tracheal Tumor and Stenosis

The efficacy of tracheal stents (TSs) in treating malignant tracheal stenosis is often compromised by tumor overgrowth, leading to restenosis and other stent-related complications that conventional chemotherapy and commercial stents fail to adequately address. Drug-loaded tracheal stents have the potential to deliver chemotherapeutics directly to tumors while relieving stenosis, but their effectiveness has yet to be studied in vivo. The design of drug-loaded tracheal stents adapting to lesions to achieve optimal antitumor effects and minimal side effects remains an area worth exploring. In this study, a lesion-adaptive bionic tracheal stent (PTX-TS) designed for the dual purpose of treating tracheal tumors and associated stenosis was developed. This novel PTX-TS was evaluated using an orthotopic rabbit model of malignant tracheal stenosis, newly established in this study. The rabbit lesions were precisely scanned using computed tomography (CT) for 3D reconstruction, enabling the design of a PTX-TS that fit both the tumor and airway dimensions to ensure complete tumor coverage and effective dilation of the stenotic airway. The PTX-TS featured a bilayer structure including a surface layer of PTX/ethylene-vinyl acetate copolymer (EVA) blends for sustained PTX release and an inner layer of polycaprolactone (PCL)/EVA blends for appropriate mechanical performance. The stent was fabricated layer by layer using a custom-built 3D printer, and the drug-loaded surface layer was printed using a novel liquid printing technique developed in our lab, achieving a high drug loading of up to 80%. The dose of the PTX-TS was investigated and set as 7.5 mg/cm2, which leads to maximum tissue permeation. With its bionic cross-sectional C-shaped structure, the PTX-TS demonstrated excellent radial flexibility, allowing successful implantation at the lesion site using a specially designed delivery apparatus, where it self-expanded to relieve stenosis. Additionally, the PTX-TS effectively delivered PTX directly to the tracheal tumor, resulting in superior antitumor efficacy without significant toxicity or complications.

Type and morphology affect the success rate of bronchoscopy for postintubation tracheal stenosis

Objective

With advancements in respiratory interventional techniques, bronchoscopic intervention technology has emerged as a viable approach for managing postintubation tracheal stenosis (PITS). However, there was a paucity of research investigating the potential impact of stenosis characteristics and morphology (such as stenosis degree, length, type, and morphology) on bronchoscopic intervention treatment prognosis for PITS patients. This study was to assess the impact of various preoperative stenosis characteristic factors on the bronchoscopic cure rate among patients.

Methods

This is a retrospective study analyzing the medical records of patients with PITS who received bronchoscopic intervention at the tertiary interventional pulmonology center.

Results

Among the cases, 115 individuals achieved a in a success rate of 79.86% for bronchoscopic intervention therapy and were assigned to Group S. On the other hand, 29 cases required surgical intervention, accounting for a surgical treatment rate of 20.14% and were assigned to Group F. The stenosis in the Group F predominantly exhibited irregular shapes with scar granulation accompanied by tracheal chondromalacia collapse. Patients in group S experienced fewer total procedures, rigid bronchoscopy treatment, intraoperative hypoxemia, needed emergency re-bronchoscopy in 24 h and transferred to ICU postoperatively. Patients with pure scar and granuloma, the rate of bronchoscopic success cure was higher than patients with scar granulation accompanied by tracheal chondromalacia (odds ratio: 8.208; 95% confidence interval: 2.755-24.459), and regular stenosis morphology was associated with a higher bronchoscopic success cure rate (odds ratio: 9.463; 95% confidence interval: 3.128-28.623).

Conclusion

Irregular airway stenosis, chondromalacia or airway collapse are key factors affecting the success rate of bronchoscopic treatment for post-intubation tracheal stenosis. Level of evidence: 4 (historically controlled studies).

World Association for Bronchology and Interventional Pulmonology (WABIP) guidelines on airway stenting for malignant central airway obstruction

Malignant Central Airway Obstruction (MCAO) encompasses significant and symptomatic narrowing of the central airways that can occur due to primary lung cancer or metastatic disease. Therapeutic bronchoscopy is associated with high technical success and symptomatic relief and includes a wide range of airway interventions including airway stents. Published literature suggests that stenting practices vary significantly across the world primarily due to lack of guidance. This document aims to address this knowledge gap by addressing relevant questions related to airway stenting in MCAO. An international group of 17 experts from 17 institutions across 11 countries with experience in using airway stenting for MCAO was convened as part of this guideline statement through the World Association for Bronchology and Interventional Pulmonology (WABIP). We performed a literature and internet search for reports addressing six clinically relevant questions. This guideline statement, consisting of recommendations addressing these six PICO questions, was formulated by a systematic and rigorous process involving the evaluation of published evidence, augmented with expert experience when necessary. Panel members participated in the development of the final recommendations using the modified Delphi technique.

ERJ Advances: interventional bronchoscopy

The field of interventional bronchoscopy is rapidly growing, with the development of minimally invasive approaches and innovative devices to diagnose and treat a spectrum of respiratory diseases (figure 1 ), often as outpatient procedures, and supported by high quality collaborative research. This short review covers aspects related to COPD, peripheral pulmonary nodules, interstitial lung disease, and airway stenosis and malacia.

This ERJ Advances article summarises the latest developments in the rapidly advancing field of interventional bronchoscopy https://bit.ly/44Qvgrm

Airway collapse hinders recovery in bronchoscopy therapy for postintubation tracheal stenosis patients

BACKGROUND

Expiratory central airway collapse (ECAC) following postintubation airway stenosis (PITS) is a rare phenomenon. The impact of airway malacia and collapse on the prognosis and the success rate of bronchoscopic interventional therapy in patients with PITS had been inadequately investigated.

OBJECTIVE

The aim of this research was to assess the influence of airway malacia and collapse on the efficacy of bronchoscopic interventional therapy in patients with PITS.

DESIGN

This retrospective analysis examined the medical documentation of individuals diagnosed with PITS who underwent bronchoscopic intervention at the tertiary interventional pulmonology center of Emergency General Hospital from 2014 to 2021.

MAIN OUTCOME MEASURES

Data pertaining to preoperative, perioperative, and postoperative stages were documented and subjected to analysis.

RESULTS

The patients in malacia and collapse group (MC group) exhibited a higher frequency of perioperative complications, including intraoperative hypoxemia, need for reoperation within 24 h, and postoperative intensive care unit admission rate (P < 0.05, respectively). Meanwhile, patients in group MC demonstrated significantly worse postoperative scores (higher mMRC score and lower KPS score) compared to those in pure stenosis group (P < 0.05, respectively), along with higher degrees of stenosis after treatment and a lower success rate of bronchoscopic intervention therapy cured (P < 0.05, respectively). Pearson analysis results showed that these terms were all significantly correlated with the occurrence of airway malacia and collapse in the airway (P < 0.05, respectively).

CONCLUSION

The presence of malacia or collapse in patients with PITS was associated with increased perioperative complications following bronchoscopic interventional therapy, and significantly reduced the long-term cure rate compared to patients with pure tracheal stenosis. Trial registration Chinese Clinical Trial Registry on 06/12/2021.

REGISTRATION NUMBER

ChiCTR2100053991.

Patient-specific airway stent using three-dimensional printing: a review

The primary function of an airway stent is to reestablish patency, impeding restenosis, supporting the tracheobronchial wall, or occluding fistulas. But stent-related complications are prevalent and can have devastating consequences. For this reason, stents are considered a last resort when there are no alternatives in treatment. Additionally, commercially available airway stents often poorly fit patients with complex airways, and they can cause various complications. At the end of the 20th century, three-dimensional (3D) printing technology was created. It has been transformative in healthcare and has been used in several applications. One of its first utilizations was the anatomical modeling of body structures that helps preoperative planning. In respiratory medicine, this technology has been essentially used in central airway diseases to produce 3D airway models and to create airway splints and prostheses. In the last decade, it has led to a transformation and allowed progress in personalized medicine, making patient-specific stents for individuals with complex airway problems. A patient-specific stent using 3D printing may minimize complications, improve quality of life, and reduce the need for repeated procedures. This review describes the recent advances in 3D printing technology, its use for developing airway prostheses to treat complex airway diseases, and the current evidence that supports its use.

Patient-Specific 3D-Printed Low-Cost Models in Medical Education and Clinical Practice

3D printing has been increasingly used for medical applications with studies reporting its value, ranging from medical education to pre-surgical planning and simulation, assisting doctor-patient communication or communication with clinicians, and the development of optimal computed tomography (CT) imaging protocols. This article presents our experience of utilising a 3D-printing facility to print a range of patient-specific low-cost models for medical applications. These models include personalized models in cardiovascular disease (from congenital heart disease to aortic aneurysm, aortic dissection and coronary artery disease) and tumours (lung cancer, pancreatic cancer and biliary disease) based on CT data. Furthermore, we designed and developed novel 3D-printed models, including a 3D-printed breast model for the simulation of breast cancer magnetic resonance imaging (MRI), and calcified coronary plaques for the simulation of extensive calcifications in the coronary arteries. Most of these 3D-printed models were scanned with CT (except for the breast model which was scanned using MRI) for investigation of their educational and clinical value, with promising results achieved. The models were confirmed to be highly accurate in replicating both anatomy and pathology in different body regions with affordable costs. Our experience of producing low-cost and affordable 3D-printed models highlights the feasibility of utilizing 3D-printing technology in medical education and clinical practice.

Establishing a novel model of malignant airway stenosis in rabbit

Background

Malignant central airway stenosis is a life-threatening condition. However, treatment of malignant airway stenosis remains challenging. There is currently a severe lack of an excellent animal model of malignant airway stenosis to facilitate treatment approaches. This is the first study to establish a rabbit model of malignant airway stenosis for bronchoscopic interventional studies.

Materials and methods

New Zealand White rabbits were used in this study, randomly divided into group A (18 rabbits) and group B (6 rabbits). A VX2 fragment suspension was injected into the submucosal layer of rabbits’ airway by bronchoscopy. Bronchoscopic examinations were performed once a week after VX2 tumor implantation to observe tumor growth and the degree of airway stenosis. Randomly, three rabbits were generally dissected after a weekly bronchoscopic examination in group A. The rabbits that reached grade III airway stenosis underwent stent implantation in group B.

Results

A total of 24 rabbits were successfully implanted with the VX2 fragment suspension in the airway without significant adverse events, and the success rate of the tumor growth was 100%. The degree of airway stenosis reaching grade III took 2 to 3 weeks after implantation of the VX2 tumor. The median survival time of rabbit models without stent implantation and rabbits with stent implantation was 32.5 and 32.0 days, respectively.

Conclusions

The implanting method is safe and effective for the establishment of a rabbit model of malignant airway stenosis. When the tumor grows to 2 to 3 weeks, the rabbit model is available for stent implantation. We recommend the models for more preclinical animal studies on bronchoscopic interventional treatments.

Mathematical surface function-based design and 3D printing of airway stents

BACKGROUND

Three-dimensional (3D) printing is a method applied to build a 3D object of any shape from a digital model, and it provides crucial advantages especially for transferring patient-specific designs to clinical settings. The main purpose of this study is to introduce the newly designed complex airway stent models that are created through mathematical functions and manufactured with 3D printing for implementation in real life.

METHODS

A mathematical modeling software (MathMod) was used to design five different airway stents. The highly porous structures with designated scales were fabricated by utilizing a stereolithography-based 3D printing technology. The fine details in the microstructure of 3D printed parts were observed by a scanning electron microscope (SEM). The mechanical properties of airway stents with various designs and porosity were compared by compression test.

RESULTS

The outputs of the mathematical modeling software were successfully converted into 3D printable files and airway stents with a porosity of more than 85% were 3D printed. SEM images revealed the layered topography of high-resolution 3D printed parts. Compression tests have shown that the mathematical function-based design offers the opportunity to adjust the mechanical strength of airway stents without changing the material or manufacturing method.

CONCLUSIONS

A novel approach, which includes mathematical function-based design and 3D printing technology, is proposed in this study for the fabrication of airway stents as a promising tool for future treatments of central airway pathologies.

Treatment of aerodigestive fistulas with a novel covered metallic Y-shaped segmented airway stent customized with the assistance of 3D printing

Background

The management of aerodigestive fistula remains challenging. An airway stent that matches well with the individual geometry of the airway is needed for the treatment of the aerodigestive fistula. This study aimed to evaluate the feasibility of a novel covered metallic segmented Y-shaped airway stent customized with the assistance of 3D printing in aerodigestive fistulas involving the carina and distal bronchi and to compare the flexibility of the novel stent with the conventional wholly knitted stent.

Methods

In the flexibility study, we measured the longitudinal bending force and spring-back force of the segmented stent and wholly knitted stent. Patient-specific stents that were individually customized with the assistance of 3D printing technology were implanted in 26 patients with aerodigestive fistulas. The technical success, clinical success, Karnofsky performance status (KPS), and stent-related complications were recorded.

Results

The bending force and spring-back force of the segmented stent were significantly lower than those of the wholly knitted stent. Stent deployment was technically successful in all patients. Clinical success was obtained in 21 patients. The KPS of patients after the stenting procedure improved significantly compared with that before stenting (P<0.001). During follow-up, granulation tissue proliferation, sputum retention, stent migration, and intolerance of the stent were found in 2, 5, 1, and 1 patient, respectively.

Conclusions

The segmented metallic Y-shaped airway stent had greater flexibility than the wholly knitted stent in an ex vivo setting. Implantation of the segmented stent individually customized with the aid of 3D printing is feasible in treating aerodigestive fistulas involving the carina and bronchi distal to the carina.