Tracheal granulation tissue. A study of bacteriology

Advances in studies on tracheal stent design addressing the related complications

Tracheal stents can be used to quickly reconstruct the airway and relieve symptoms of dyspnea in patients with tracheal stenosis. However, existing tracheal stents lead to complications such as granulation tissue formation, difficulty in removal, persistent growth of malignant tumors, stent migration, and mucus plugging. In this article, we reviewed the main methods used to reduce complications associated with tracheal stent design. Drug-eluting stents can inhibit granulation tissue formation and prevent infection and local chemotherapy. The biodegradable stent can support the trachea for some time, maintain tracheal patency, and degrade gradually, which avoids removing or replacing the stent. Radioactive stents loaded with I125 have good potential for inhibiting the persistent growth of malignant tumors. Three-dimensional printing technology enables the manufacturing of patient-specific stents, which increases the degree of matching between the complex tracheal anatomy and the stent, thus providing a new solution for stent migration caused by structural mismatch. Minimizing the barrier of the stent to mucociliary clearance, providing an anti-fouling coating, and culturing respiratory epithelial cells on the surface of the stent are the main methods used to reduce mucus plugging. We also proposed future research directions for tracheal stents to guide the design and manufacture of ideal tracheal stents.

Myeloid Phenotypes in Tracheostomy-Associated Granulation Tissue

OBJECTIVE(S)

Tracheostomy-associated granulation tissue is a common, recurrent problem occurring secondary to chronic mucosal irritation. Although granulation tissue is composed of predominantly innate immune cells, the phenotype of monocytes and macrophages in tracheostomy-associated granulation tissue is unknown. This study aims to define the myeloid cell population in granulation tissue secondary to tracheostomy.

METHODS

Granulation tissue biopsies were obtained from 8 patients with tracheostomy secondary to laryngotracheal stenosis. Cell type analysis was performed by flow cytometry and gene expression was measured by quantitative real-time polymerase chain reaction. These methods and immunohistochemistry were used to define the monocyte/macrophage population in granulation tissue and were compared to tracheal autopsy control specimens.

RESULTS

Flow cytometry demonstrated macrophages (CD45+CD11b+) and monocytes (CD45+FSClow SSClow ) represent 23.2 ± 6% of the granulation tissue cell population. The M2 phenotype (CD206) is present in 77 ± 11% of the macrophage population and increased compared to the M1 phenotype (p = 0.012). Classical monocytes (CD45+CD14high CD16low ) were increased in granulation tissue compared to controls (61.2 ± 7% and 30 ± 8.5%, p = 0.038). Eighty-five percent of macrophages expressed pro-inflammatory S100A8/A9 and 36 ± 4% of macrophages co-localized CD169, associated with tissue-resident macrophages. M2 gene expression (Arg1/CD206) was increased in granulation tissue (3.7 ± 0.4, p = 0.035 and 3.5 ± 0.5, p = 0.047) whereas M1 gene expression (CD80/CD86) was similar to controls (p = 0.64, p = 0.3). Immunohistochemistry of granulation tissue demonstrated increased cells co-localizing CD11b and CD206.

CONCLUSIONS

M2 macrophages are the dominant macrophage phenotype in tracheostomy-associated granulation tissue. The role of this cell type in promoting ongoing inflammation warrants future investigation to identify potential treatments for granulation tissue secondary to tracheostomy.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:2346-2356, 2023.

Protective effects of different anti‑inflammatory drugs on tracheal stenosis following injury and potential mechanisms

Tracheal stenosis following injury cannot be effectively treated. The current study compared the protective effects of different anti-inflammatory drugs on tracheal stenosis and investigated their possible mechanisms. Rabbit tracheal stenosis models following injury were constructed and confirmed using hematoxylin and eosin (H&E) staining. A total of 30 rabbits were divided into the control (CON), penicillin (PEN), erythromycin (ERY), budesonide (BUD) and PEN + ERY + BUD groups (n=6). Stenotic tracheal tissue, serum and bronchoalveolar lavage fluid (BALF) were collected 10 days after continuous treatment. Pathological changes in the tracheas were observed by H&E staining. Histone deacetylase 2 (HDAC2) expression in tracheal tissues was detected by immunofluorescence. Immunohistochemistry was performed to detect collagen I (Col-I) and collagen III (Col-III) levels in tracheal tissues. Transforming growth factor β1 (TGF-β1), vascular endothelial growth factor (VEGF) and interleukin 8 (IL-8) levels in serum and BALF samples were determined using ELISA kits. Western blotting detected HDAC2, IL-8, TGF-β1 and VEGF levels in tracheal tissues. H&E staining demonstrated that tracheal epithelial hyperplasia and fibroblast proliferation in the ERY and PEN + ERY + BUD groups markedly improved compared with the CON group. Furthermore, in tracheal tissues, HDAC2 expression was significantly increased and IL-8, TGF-β1, VEGF, Col-I and Col-III levels were significantly decreased in the ERY and PEN + ERY + BUD groups compared with the CON group. Additionally, the results for the PEN + ERY + BUD were more significant compared with the ERY group. In serum and BALF samples, IL-8, TGF-β1 and VEGF levels in the ERY and PEN + ERY + BUD groups were significantly lower compared with the CON group, with the results of the PEN + ERY + BUD group being more significant compared with the ERY group. There were no significant differences between the PEN, BUD and CON groups. ERY inhibited tracheal granulation tissue proliferation and improved tracheal stenosis following injury and synergistic effects with PEN and BUD further enhanced these protective effects. The mechanism may involve HDAC2 upregulation and inhibition of local airway and systemic inflammatory responses.

Bronchial stenting in infants with severe bronchomalacia: Technique and outcomes

OBJECTIVES

To report the first use of a balloon expandable bare metal stent for treating infant bronchomalacia.

BACKGROUND

Infant bronchomalacia often requires prolonged mechanical ventilation and can be life-threatening. Effective treatment for severe infant bronchomalacia continues to be elusive. We present three cases of bronchial stenting for no-option or treatment refractory infant bronchomalacia.

METHODS

Three consecutive cases of stenting to relieve conservative treatment refractory severe infant bronchomalacia were performed between February 2019 and December 2020. Initial diagnosis was confirmed with Computed Tomography (CT) angiography. Patients underwent rigid micro laryngoscopy, bronchoscopy, and flexible bronchoscopy to evaluate the airway. Initial conservative management strategies were pursued. Patients failing initial conservative management strategies were considered for rescue bronchial stenting.

RESULTS

Our initial clinical experience with a coronary bare metal stent for these procedures has been favorable. The stent was easy to deploy with precision. We did not encounter stent embolization or migration. There was sufficient stent radial strength to relieve bronchomalacia without causing restenosis or erosion. There was no significant granulation tissue formation. In one patient, the stent was removed after 12 months of somatic growth; this was uneventful and bronchial patency was maintained. There were no complications in any of our patients regarding stent placement and reliability.

CONCLUSION

In cases of three infants with severe bronchomalacia, we found that bronchial stenting with the bare metal coronary stent was effective in relieving bronchial stenosis.

Feasibility of shotgun metagenomics to assess microbial ecology of pediatric tracheostomy tubes

OBJECTIVE

Biofilm formation on medical devices such as tracheostomy tubes (TTs) is a serious problem. The clinical impact of biofilms on the airway is still unclear. Biofilms may play a role in granulation tissue development, recurrent airway infections, and failure of laryngotracheal reconstructions. The microbial ecology on TTs has yet to be elucidated. The purpose of this study was to determine the feasibility of shotgun metagenomics to assess the biodistribution of microorganisms on TTs.

METHODS

Four TTs were collected from pediatric patients (1.4-10.2 years) with (n = 2) and without (n = 2) granulation tissue formation. Duration of TT placement prior to retrieval from patients ranged from 5 to 365 days. DNA extraction was performed using the MO BIO UltraClean Microbial Isolation (Mo Bio Laboratories, Carlsbad, CA). Library generation using Nextera XT adapters (Illumina Inc., San Diego, CA) and metagenomic shotgun sequencing was performed using the Illumina NextSeq500 (Illumina Inc, San Diego, CA). Salinibacter ruber, a species not found in mammalian microbiome communities, was used as a DNA standard and represented 0.7% to 5.7% of the microbiome, ensuring good quality and abundance of sample DNA.

RESULTS

Metagenomic shotgun sequencing was successful for all patients. In TTs associated with granuloma, Fusobacterium nucleatum, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae were predominant, most of which are considered pathogens. From TTs without granulomas, Neisseria mucosa, Neisseria sicca, Acinetobacter baumannii, and Haemophilus parainfluenzae were identified, primarily consistent with respiratory microbiome.

CONCLUSION

This study reveals that metagenomic shotgun sequencing of biofilms formed on pediatric TTs is feasible with an apparent difference in microbiome for patients with granulation tissue. Further studies are necessary to elucidate the pathogenesis of microbial ecology and its role in airway disease in patients with TTs.

LEVEL OF EVIDENCE

2c Laryngoscope, 129:317-323, 2019.

Microbiology of Tracheal Secretions: What to Expect with Children and Adolescents with Tracheostomies

Introduction  People with tracheostomies exhibit a higher risk of colonization of the lower respiratory tract, acute tracheitis and pneumonia. Despite this, the culture of tracheal secretions is not a routine in most hospitals, and sometimes empiric therapy is based on personal experience, which is not an ideal situation.

Objective  To recognize the pathogens present in the tracheal secretions collected from people up to 18 years old with tracheostomies.

Methods  Prospective evaluation of patients under the age of 18 of a tertiary care hospital. A standardized questionnaire was completed, and tracheal secretion aspirates were sent for microbiological cultures and antibiograms.

Results  Twenty patients under 18 years of age were evaluated, 65% of whom were male. The microbiological culture was positive in 90% of the patients, and the most common microorganisms found were Pseudomonas aeruginosa (55.5%) and Staphylococcus aureus (27.7%).

Discussion  Tracheostomized children and adolescents have respiratory tracts colonized by pathogens, the most common of which is Pseudomonas aeruginosa . These patients must undergo tracheal secretion cultures, whether they present symptoms or not, to determine if there is a correlation between the colonization and the infections. This finding could guide the adequate treatment, avoiding the inappropriate use of antibiotics and indicating the better therapy in cases of laryngeal reconstruction.

Conclusion  In this sample, the culture of tracheal secretions was mainly positive, and the most common agent was P. aeruginosa . We suggest the routine access to Brazilian children and adolescents tracheal secretion cultures, which could help to make a profile of these children and guide the use of antibiotics.

Bacterial biofilms and increased bacterial counts are associated with airway stenosis

OBJECTIVES

Most airway stenoses are acquired secondary to the use of prolonged endotracheal intubation. Antibiotics have been shown to decrease local inflammation and granulation tissue formation in the trachea. However, antibiotic therapy is not 100% effective in preventing or treating granulation tissue formation. Development of bacterial biofilms may explain this finding. This study evaluates the difference between tracheal stenotic segments and normal trachea in terms of (1) presence of bacterial biofilms, (2) quantitative bacterial counts, and (3) inflammatory markers.

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary care academic medical center.

SUBJECTS

A total of 12 patients were included in the study. Tissue from stenotic segments from 6 patients with airway stenosis undergoing open airway procedures were compared with tracheal tissue from 6 patients without airway stenosis undergoing tracheostomy.

METHODS

Scanning electron microscopy for biofilm detection, quantitative polymerase chain reaction for quantitative analysis of bacterial count, and immunohistochemistry were performed for inflammatory markers transforming growth factor β1 (TGF-β1) and SMAD3.

RESULTS

Compared with the patients without airway stenosis, patients in the airway stenosis group showed presence of bacterial biofilms, a significantly higher expression of 16S rRNA gene copies per microgram of tissue (187.5 vs 7.33, P = .01), and higher expression of TGF-β1 (91% vs 8%, P < .001) and SMAD3 (83.5% vs 17.8%, P < .001).

CONCLUSION

Bacterial biofilms, increased bacterial counts, and higher expression of TGF-β1 and SMAD3 are associated with airway stenosis.

Penicillium species as a rare isolate in tracheal granulation tissue: a case series

Introduction

Granulation tissue formation is a major problem complicating the treatment of upper airway stenosis. We present two cases of recurrent tracheal granulation tissue colonisation by Penicillium species in patients undergoing laryngotracheal reconstructive surgery for post-intubation tracheal stenosis. We believe that although most Penicillium species do not cause invasive disease they can be a contributory factor to the occurrence of upper airway stenosis.

Case presentation

A microbiological and mycological study of tracheal granulation tissue in two patients with recurrent laryngotracheal stenosis was carried out. Penicillium species was seen microscopically and cultured from tracheal granulation tissue. Neither patient grew any bacteria known to be associated with airway granulation tissue formation. Amphotericin B, itraconazole, flucytosine voriconazole and caspofungin were highly active against both isolates.

Conclusion

A search for a fungal cause should form part of the investigation for recurrent tracheal granulation tissue during laryngotracheal reconstruction.

Microbiology of Stents in Laryngotracheal Reconstruction

OBJECTIVES

Granulation tissue often forms around a laryngotracheal stent, tracheostomy tube, or other airway prosthesis, especially if infection occurs. We studied the types and frequency of organisms colonizing stents used in pediatric laryngotracheal reconstruction.

STUDY DESIGN

This prospective study included 21 patients undergoing 23 consecutive laryngotracheal reconstructions with stents between 1991 and 1999.

METHODS

After endoscopic removal, each laryngotracheal stent was placed immediately in a sterile container and transported to the laboratory. Specimens for culture were obtained from biofilms on the stents and plated on agars for growth of aerobic, anaerobic, and fungal organisms. Culture results were analyzed with regard to patient age, duration of stenting, and graft type.

RESULTS

All stents were colonized with more than one pathogen (range 2-7). The most frequent aerobic isolates were Streptococcus viridians, Pseudomonas aeruginosa, Staphylococcus aureus,Haemophilus influenza, and Neisseria species. Anaerobic organisms were isolated in 26% of cases. Candida species were isolated in 57% of the cases; patients whose stents were colonized with Candida were significantly (P =.007) older (mean 77.5 months) than those not colonized with this organism (mean 26.1 months)

CONCLUSIONS

The antibiotic agents currently used for children undergoing laryngotracheal reconstruction target mainly aerobic organisms. Despite prophylactic measures, the incidence of granulation tissue formation is clinically significant, and the prevalence of anaerobic, including fungal, pathogens is high. Antibiotic therapy directed toward controlling anaerobic and fungal organisms could help in controlling local inflammation and thus granulation tissue formation.

Bacteria and granulation tissue associated with Montgomery T-tubes

OBJECTIVES

Although complications (infection, development of granulation tissue) of silicone Montgomery T-tubes have been reported, the microbiological consequences and the origin of granulation tissue have not yet been evaluated.

STUDY DESIGN

A prospective trial.

METHODS

Twenty-three Montgomery T-tubes from 10 patients were analyzed with regard to the development of granulation tissue, bacterial growth (including genotyping with polymerase chain reaction), and results of sensitivity testing. Furthermore, stent sterilization (n = 6) was investigated.

RESULTS

Granulation tissue occurred with 74% of the stents, and all specimens showed signs of infection but no foreign body reaction. The predominant organisms were Staphylococcus aureus (35%) and Pseudomonas aeruginosa (17%). The differences between groups with and without granulation tissue were significant for P aeruginosa. Polymerase chain reaction fingerprinting of the S aureus obtained from 15 stents (n = 3 patients) revealed a total of seven different genotypes. Whereas two of these patients harbored six different genotypes of S aureus, the third patient was persistently colonized by S aureus over a 15-month period with the identical genotype. Susceptibility testing showed most commonly (65%) sensitivity to a combination of amoxicillin-clavulanate and ofloxacin. After sterilization, 92% of analyzed stent segments showed no bacterial growth.

CONCLUSIONS

Granulation tissue commonly occurred next to the silicone (subglottic area, stoma) where S aureus and P aeruginosa were commonly isolated. A combination of mechanical irritation and bacterial infection seems to account for the development of granulation tissue. Polymerase chain reaction fingerprinting showed both prolonged persistence and a change of colonizing strains after multiple stent replacements. A combination of amoxicillin-clavulanate and ofloxacin is the most effective antibiotic therapy. Sterilization of the cost-intensive silicone stents is feasible, and reuse in the same patient is justifiable from economic aspects.

Regular tracheostomy tube changes to prevent formation of granulation tissue

OBJECTIVES/HYPOTHESIS

Tracheostomy is a commonly performed operative procedure that has been described since 2000 B.C. The early indications for tracheostomy were for upper airway obstruction, usually occurring in young people as a result of an infectious process. Recently, tracheostomies are more commonly performed in the critically ill patient to assist in long-term ventilatory support. Granulation tissue at the stoma and the trachea has been described as a late complication resulting in bleeding, drainage, and difficulty with maintaining mechanical ventilatory support.

STUDY DESIGN

The present report is of an observational study of a newly implemented policy that required regular changing of tracheostomy tubes. Comparable groups of patients were compared before and after this procedural change to document complications. Data collection consisted of chart reviews of all admissions for 1 year before the policy change and the subsequent 2 years. Complication rates were compared using standard statistical techniques.

METHODS

A policy change was instituted that required all tracheostomy tubes to be changed every 2 weeks in conjunction with a detailed evaluation of the tracheostomy stoma. Charts were reviewed the year before the change in policy and in the subsequent 2 years to determine the incidence of granulation tissue requiring operative intervention.

RESULTS

The number of patients requiring surgical intervention secondary to granulation tissue showed a statistically significant decrease (P =.02). A review of policies and procedures from the six largest hospitals in southeastern Michigan had no recommendations for routine tracheostomy tube changes.

CONCLUSIONS

A policy requiring a routine change of tracheostomy tubes results in fewer complications from granulation tissue. Tracheostomy tube changes to prevent granulation tissue and its complications.

The role of airway stents in the management of pediatric tracheal, carinal, and bronchial disease

OBJECTIVE

A variety of stents are available to aid in the management of complex tracheal, carinal and bronchial stenoses. We reviewed our multi-institutional experience with airway stents in children.

METHODS

Thirty-three children (age, 13 days-18 years) from four institutions have had a total of 40 stents placed to aid in the management of complex airway stenoses. Three stent types were utilized: 29 silastic stents, five expandable metal stents and six customized carinal stents (four patients had two stents and one patient had four stents). Thirty children had tracheal stents, six children had bronchial stents, and two infants had carinal stents (three children had stenting of more than one area and two had stenting of all three locations). Twenty-eight patients (age, 5 months-18 years; mean, 8.06 years; SEM, 1.13 years) had stents placed after a variety of airway reconstructive procedures. Four underwent stenting in a non-operative setting and one as preoperative stabilization.

RESULTS

Twenty-seven patients survived. One patient died early due to bleeding. Five patients died late: two due to bleeding, one from mediastinitis, and two patients with functional airways died late from unrelated problems. Complications are related to stent type and location. Carinal stents can migrate; several techniques are available to help manage this problem. Wire stents are essentially non-removable requiring periodic dilation. Silastic stents stimulate granulation tissue formation requiring periodic bronchoscopic removal.

CONCLUSION

Tracheal stenting can aid in the management of pediatric airway problems. Complications are common, but can be managed with appropriate intervention.

Obstructive suprastomal granulation tissue following percutaneous tracheostomy

Percutaneous dilatational tracheostomy is frequently performed as an alternative to traditional surgical open tracheostomy with many reported benefits. Despite its relative safety and widespread acceptance, complications can be associated with the procedure itself or long-term. We present four cases where there was difficulty with decannulation because of exuberant obstructive granulation tissue. In each case, the percutaneous tracheostomy involved the cricoid cartilage.

Can topical mitomycin prevent laryngotracheal stenosis?

OBJECTIVES/HYPOTHESIS

Early topical application of mitomycin to a laryngotracheal lesion may prevent or reduce laryngotracheal stenosis (LTS).

STUDY DESIGN

Prospective controlled animal study.

METHODS

LTS was induced in 60 dogs randomly assigned to four groups. Controls received an immediate topical application of normal saline. The suction-control group received an immediate application of normal saline followed by suction of secretions on day 2. The mitomycin group received immediate application of 0.7 mL mitomycin (0.2 mg/mL). The repeat-mitomycin group received an immediate application of mitomycin and a second application on day 2, after secretions were suctioned. The laryngeal lumens were measured endoscopically at baseline, day 12, and day 21. Animals were euthanatized if stenosis approximated 95% or at day 21.

RESULTS

All dogs in the mitomycin groups survived to day 21, compared with 12 in the suction group and only 2 controls. No side effects of mitomycin were observed. At day 21, surviving controls had 85% and 95% stenosis. In the mitomycin group, median stenosis was 27% (interquartile range, 29% to 42%); in the repeat-mitomycin group, 30% (22% to 40%); and in the suction-control group, 84.5% (72.5% to 93.5%). The mitomycin group differed significantly from controls on day 12 (median difference = 85%, 95% CI = 80%-94%, P < .0001) and day 21 (difference = 63.9%, 95% CI = 58%-85%, P = .031).

CONCLUSION

A single topical application of mitomycin significantly reduces the severity of LTS in dogs. Reapplication after 2 days does not improve results. Prospective clinical studies are warranted to assess the efficacy in humans.

Tissue compatibility and biodegradation of new absorbable stents for tracheal stabilization: an experimental study

Newly designed absorbable stents for temporary tracheal stabilization were implanted into the trachea of 35 Wistar rats. The stents consisted of Vicryl filaments in a homogeneous PDS melt. Compatibility and biodegradation were investigated over a study period of up to 24 weeks. After the animals were killed, the trachea was examined with an optic and scanning electron microscope. During the first 2 weeks erosive mucosal defects appeared in the trachea, as well as distinct polyps of granulation tissue, focal metaplasia of the epithelium, and inflammatory infiltrates of the lamina propria. During the period leading to the sixth week, the granulations flattened and mild fibrotic alterations evolved. After the eighth week no stent residues could be detected, whereas only slight signs of chronic fibrotic inflammation persisted. No evidence for aspiration of foreign bodies or progressive inflammatory changes of the mediastinum was found.

Microbiology of tracheal granulation tissue associated with silicone airway prostheses

Granulation tissue formation and contraction is inevitable during the healing of open wounds. The presence of infection and a foreign body, such as a silicone airway prosthesis or other tracheotomy tube, magnifies this response. In airway reconstruction, wound contraction secondary to chronic inflammation is a liability. Cultures of granulation tissue were taken from 12 patients with silicone cannulas of T-Tubes. Polymicrobial colonization predominated, with variable combinations of gram-positive, gram-negative, and anaerobic organisms being present. On the basis of sensitivity data, amoxicillin-clavulanate potassium and ciprofloxacin hydrochloride were chosen as empirical antimicrobials. Anecdotally, impressive decreases in the quantity of granulation tissue were seen. We recommend a prospective trial to more accurately define the role of antibiotics in this setting.

The fate of the skin graft in laryngoplasty

In laryngoplasty procedures, laryngotracheal soft tissue defects are often repaired using skin grafts. While stenting is necessary to approximate and immobilize the graft, prolonged stenting causes increased bacterial counts, granulation tissue formation, tissue ischemia, and graft failure. Optimal time for stent removal has not been experimentally defined. Using the ferret animal model, 24 laryngoplasty procedures were performed. The subjects were stented by group for 0, 3, 7, 14, or 28 days. Analysis consisted of quantitative bacteriology, dye perfusion, and quantitative histologic assessment of graft viability. Tissue culture results revealed that by 3 days after the procedure all groups had 10(5) CFU of bacteria per gram of tissue. Graft viability in successful procedures was maximal in the 7-day group and statistically significant from the 3-day to the 28-day groups. In conclusion, while stenting is necessary for graft adherence, prolonged exposure to local tissue sepsis leads to progressive graft destruction.

Obstruction after self-expanding metallic stents in tuberculous bronchial stenosis

Expandable metallic stents seemed to be a good method in tuberculous bronchial stenosis that does not respond to medical therapy. But there was no long-term follow-up study after stents insertion in tuberculous bronchial stenosis. We report a case of obstruction after successful Gianturco metallic stents insertion due to tuberculous bronchial stenosis.