Assessing the Safety and Efficacy of Self-Expanding Metallic Y Stents in a Community Medicine Setting

Abstract

Self-Expanding Metallic (SEM) Y stents are a newer form of stent that is gaining popularity outside the USA, but still has limited data, especially in a community medicine setting. This study analyzed efficacy and complication rates in 14 patients who had a SEM Y stent placed between August 2022 and June 2024 at Harris Methodist Hospital in Fort Worth, Texas for either central airway obstruction (CAO) or fistulae. Of the 14 patients, 11 were requiring supplemental oxygen or mechanical ventilation prior to stent placement. Post-stenting 42.9% had decreased oxygen requirements, 21.4% unchanged, 14.3% increased, and 21.4% remained on room air. Complications included mucus plugging (42.9%), infection (35.7%), and granulation tissue (14.3%). There was no statistically significant correlation between gender/age and complications (p = 0.879/0.490, respectively). Complication rates were similar when compared to silicone Y stents based on literature review. In conclusion, SEM Y stents are a safe and effective alternative stent intended for palliative treatment with similar success and complications that can be easily and effectively implemented in a community hospital, with the added benefit of being able to be placed with flexible bronchoscopy.

1. Introduction

In patients diagnosed with a pulmonary, mediastinal, or esophageal malignancy, there is a concern for central airway obstruction (CAO) or fistulae if their malignancy progresses. CAO is found in some degree in approximately 30% of lung cancer patients at the time of diagnosis [1]. Survival rate of patients with CAO is estimated to be 2–3 months without intervention but can potentially improve to 6–8 months with stenting [2]. Stenting improves outcomes in a variety of ways: relieving extrinsic compression, providing a barrier from fistulae, or by aiding in recanalization of the airway [3]. In these instances, stenting is for palliative intent only [4], as by the time obstruction occurs, malignancy has progressed to the point where resection or chemotherapy have minimal benefit [4]. Typically, if patients can undergo or qualify for a surgical resection to treat the disease, use of stenting is contraindicated [5].

Generally, there are two shapes of stent that are used, a straight stent which is intended for obstructions of the upper trachea, and Y stents which are used for obstruction near or at the level of the carina [6]. Worldwide, the standard material for these is silicone, with Dumon being a major manufacturer. These silicone stents are created from silicone elastomers or polydimethylsiloxane [7], which allow for desirable stability at higher temperatures along with minimal tissue reactivity once implanted [8]. Another benefit of the entire stent being one material is that it allows for quick and easy customization prior to placement [7]. Silicone stents are easily repositioned and removed, but at the cost having a higher risk of migration [9,10,11]. The efficacy of these stents is well documented and with good results but is criticized by its need for rigid bronchoscopy. Although generally regarded as requiring rigid bronchoscopy, there have been rare instances where flexible bronchoscopy has been used to place a silicone stent [12], but in general practice rigid bronchoscopy is standard.

Metallic stents are the other major subset of Y stents used, coming in both covered and uncovered variants. Additionally, metallic stents can be divided into self-expanding metallic (SEM) and fixed diameter, which require balloon dilation. These stents are most made from nitinol, a titanium and nickel alloy popular for is elasticity and shape memory [7]. The covered variants utilize polyurethane, polytetrafluoroethylene, or silicone, with silicone being most common [7], and are preferred to their uncovered counterparts as the covering minimizes intrinsic tissue growth [13]. Metallic stents have the benefits of a better internal to external diameter ratio, are radio-opaque, and can be placed with flexible bronchoscopy [7]. Additionally, uncovered metallic stents have an added benefit of not blocking any bronchial lobar opening, although overall the role of uncovered stents limited [14]. Despite these benefits to metallic stents, they have shown to be more difficult to remove than silicone stents, with high risk of mucosal damage during removal [13].

Over the past few years, Self-Expanding Metallic (SEM) Y stents (Figure 1) have been used, with similar efficacy rates as silicone stents [1,15]. However, the data is sparse as these stents have primarily been used at large academic centers outside of the USA, with the first reported use of a SEM Y stent in the USA being in April 2022 [16]. Although limited, these studies outside the USA have been promising in showing that these SEM alternatives are not only equally as effective, but also do not pose any increased risk of complications. This article aims to study SEM efficacy and complications in a community hospital setting in the USA and compare them to available data of silicone stents. The overall hope is to provide confidence to physicians outside large academic centers in the USA that SEM Y stents are an effective alternative to consider.

2. Methods

2.1. Study Setting and Design

This is a single center, retrospective observational study at a community hospital with 14 patients with benign or malignant central airway disease who underwent SEM Y stent placement. All stents were placed at Texas Health Harris Methodist Hospital in Fort Worth, TX. The study period was from August 2022 to June 2024. IRB review and exemption was received from the University of Texas Southwestern Medical Center. We utilized a SEM Y stent manufactured by Thoracent, which are made from nitinol wire mesh covered with silicone.

We collected data as follows: (i) patient demographics, (ii) indication for SEM Y stent placement, (iii) procedural details, (iv) complications, and (v) duration of stent placement prior to removal, discharge, or transition to hospice. Inclusion criteria was placement of SEM Y stent for any reason. There were no exclusion criteria. Complications were mucus plugging, infection (instances of pneumonia), granulation tissue accumulation that required debulking, and stent migration.

The primary endpoint was to assess the efficacy of SEM Y stents in patients with respiratory distress in the setting of benign and malignant central airway disease. The secondary endpoint was to assess the rate of complications associated with SEM Y stents in terms of mucus plugging, infections, granulation tissue formation requiring debulking, and stent migration when compared to silicone Y stents. Mucus plugging is described as an obstruction leading to poor ventilation and oxygenation, that is confirmed and treated with bronchoscopy. Instances of infection is bacterial pneumonia, and date of onset is determined when symptoms first arise (fevers, leukocytosis, etc.) and is confirmed with cultures received either by expectorated sputum or via bronchioalveolar lavage (BAL). Presence of granulation tissue was not routinely surveyed due to the nature of most patients’ discharge. Granulation tissue is described as the presence of tissue causing obstruction and interfering with ventilation and oxygenation, requiring intervention and debulking.

Descriptive data as described above was gathered via chart review as well as through flowsheets documenting patient vitals and oxygen requirements. Fisher’s Exact Test was used to assess for any significant correlation between gender and complication rates as well as age and complications rates.

The data from our patient population was compared to patients who had received silicone Y stents. As no data for patients who had received this type of stent at our hospital was available for comparison, we procured this data by searching databases including PubMed, ScienceDirect, Cochrane Library, and Google Scholar. The goal was to find studies that both placed silicone Y stents for similar indications as our patients and tracked complication rates. Seven studies from four different countries were found and used as a comparison. As patient populations were different, no statistical analysis was able to be done comparing the two groups and thus the comparison is purely observational.

2.2. SEM Y Stent Procedural Placement in Detail

Patients were intubated with a 10.0 endotracheal (ET) tube. The fiberoptic bronchoscope was passed via the ET tube and the trachea was entered and visualized. The left and right mainstem bronchi were visualized and the full tracheobronchial tree was surveyed (Figure 2). If significant intrinsic tumor burden was present, tumor debulking was performed along with balloon dilation, if indicated (Figure 3). While under fluoroscopic guidance, the bronchoscope was used to visualize the left mainstem and the guidewire (0.035 inches in diameter, 180 cm in length) was introduced into the left mainstem. Afterwards, the bronchoscope was removed and reintroduced into the right mainstem where a second guidewire was introduced. The Y stent deployer was loaded onto the guidewire and slowly introduced into the airway via the ET tube. Under fluoroscopic visualization if needed, the stent loader was placed at the main carina and the limbs of the stent were gently deployed. The left mainstem limb was deployed first (Figure 4), and after confirming good placement, the right mainstem limb was subsequently deployed (Figure 5). Afterwards, the tracheal portion was deployed, and the stent loader and guidewires were removed from the trachea (Figure 6). A 2.8 ultra-slim bronchoscope was then utilized, and the airways were evaluated thoroughly. The stent was deemed appropriately positioned if it was observed to be sitting well in the carina with the right mainstem limb observed to be terminating at the take off to the right lobe and the left mainstem limb terminating at the take off to the left upper lobe. Bronchoalveolar lavage was subsequently performed, and all post-procedural bloody secretions were aspirated dry. A visualization of the step wise process of stent loader and guidewire placement, sequential deployment, and loader removal can be seen with the fluoroscopy images (Figure 7).

3. Results

3.1. Demographics

There were 14 patients total with ages ranged from 27 to 78 years old with a mean age of 59.4 years (SD 12.7). There were 5 males and 9 females. Primary indication for stenting was due to a malignant process, primarily for CAO (71.4%) followed by tracheoesophageal (TE) fistula (14.3%) and bronchopleural (BP) fistula (7.1%). There was one patient who had a stent placed for tracheal laceration after traumatic intubation (7.1%). Of the 13 patients with malignancy, 9 were pulumonary and 4 were non-pulmonary malignancies. Pulmonary malignancies included adenocarcinoma, squamous cell carcinoma, mesothelioma, and spindle cell carcinoma. Non-pulmonary malignancies included breast cancer, esophageal cancer, and thymic cancers (

Table 1. Demographic and clinical characteristics of SEM Y stent placement in patients between 28 October 2022–5 July 2024 (n = 14).

	N (%)
Age, mean	59.4
Gender
Male	5 (35.7)
Female	9 (64.3)
Diagnosis
Pulmonary Cancer 1	9 (64.3)
Non-Pulmonary Cancer 2	4 (28.6)
Trauma	1 (7.1)
Indication for Stent
CAO	10 (71.4)
TE Fistula	2 (14.3)
BP Fistula	1 (7.1)
Tracheal Laceration	1 (7.1)
Complications
Mucus Plugging	6 (42.9)
Infection	5 (35.7)
Granulation Tissue	2 (14.3)
Stent Migration	0 (0.0)
Supplemental Oxygen Requirement Changes
Decreased	6 (42.9)
Increased	2 (14.3)
Unchanged	3 (21.4)
Remained on Room Air	3 (21.4)
Discharge
Discharged to Hospice	10 (71.4)
Discharged to Home/Facility	3 (21.4)
Remain Hospitalized	1 (7.1)

¹ Pulmonary cancer includes adenocarcinoma, squamous cell carcinoma, mesothelioma, and spindle cell sarcoma. ² Non-pulmonary cancer includes breast, esophageal, and thymic cancers.

).

3.2. SEM Y Stent Efficacy

Most patients (78.5%) presented to the hospital in respiratory distress and required supplemental oxygen or mechanical ventilation. Three patients (21.4%) did not require any supplemental oxygen prior to stenting. After SEM Y stent placement, the three patients not requiring supplemental oxygen remained off oxygen. Of the remainder of patients, 6 (42.9%) had decreased oxygen requirements, 2 (14.3%) had increased oxygen requirements, and 3 (21.4%) had no change in requirements. (Figure 8) After stent placement, 10 patients were discharged to hospice, 3 were discharged to home or facility, and 1 remained hospitalized long enough for the stent to be removed and was still hospitalized at the time of data collection. Duration of stent placement ranged from 3 to 117 days prior to either discharge or stent removal (Mean 41.1 days, SD = 40.1) (Table 1 and

Table 2. Patient change in oxygen requirements and rate of complications.

Patient #	Age/Gender	Duration of Stent Placement 1	Change in Oxygen Requirements	Mucus Plugs (# of Days Post Placement)	Infection (# of Days Post Placement)	Granulation Tissue (# of Days Post Placement
1	27 M	110	Extubated from 40% FiO2 to 2 L NC	6, 66, 84, 86	9, 71, 90	N/A
2	65 M	117 *	RA before and after	N/A	81	117
3	65 F	3	Extubated from 40% FiO2 to 2 L NC	N/A	N/A	N/A
4	54 F	7	No change, remained intubated	N/A	N/A	N/A
5	43 F	89	8 L Facemask to 1 L NC	N/A	N/A	N/A
6	61 M	62	5 L NC to RA	27	10, 27	N/A
7	65 M	33	RA before and after	N/A	N/A	N/A
8	65 F	8	No changed, remained intubated 40% FiO2	7	N/A	N/A
9	57 F	39	Remained intubated FiO2 50% to 40%	7, 12	12	N/A
10	63 F	63	2 L NC to RA	N/A	35	N/A
11	54 F	16	RA before and after	2, 7	N/A	N/A
12	78 F	16 *	5 L NC before and after	17	N/A	16
13	61 F	8	Increased 4 L NC to 6 L NC	N/A	N/A	N/A
14	74 M	4	Extubated from 40% FiO2 to 6 L NC	N/A	N/A	N/A

¹ Duration of placement prior to either removal of stent or discharge to hospice. * Stent removed, not discharged to hospice with stent in place. NC = Nasal Cannula, RA = Room Air, FiO₂ = Fraction of inspired oxygen, N/A = no incidences recorded.

).

3.3. Complications of SEM Y Stents

Overall complication rate occurred in 57.1% of patients, with the mean time to any complication being 7 days (SD = 2.1). Mucus plugging occurred in 6 (42.9%) patients with median time between stent placement and first mucus plug being 7 days. Infection occurred in 5 (35.7%) patients, with the median time between stent placement and pneumonia diagnosis being 12 days. Formation of granulation tissue that required debulking occurred in 2 (14.3%) patients. There were no incidences of stent migration. There additionally were no procedural complications during SEM Y stent placement. The mean age of those who developed complication was 58.8 (SD = 14.7), and the mean age of those who did not develop complication was 57.6 (SD = 9.3). There was no significant association found between age and complications (p = 0.879). Additionally, there was no significant association between gender and complications (p = 0.490) (Table 1 and Table 2).

3.4. Complications of Silicone Y Stents

Literature review was conducted to analyze for rates of reported complications in patients who received silincone Y stents for similar indications as our patient set. Seven studies were found that fit these criteria. These studies originated from 4 separate countries including China, Turkey, Korea, and India. One study was a multicenter systematic review, while the remaining six were single center retrospective analyses. Most studies collected data on mucus plugging, infection, stent migration, and granulation tissue, however, not all studies reported all these complications. Additionally, while some of these complications were reported, they were sometimes not quantified. Sample sizes of the studies ranged from 9 to 46 patients, with a mean of 19. Mucus plugging ranged from 8.7% to 66.67% of patients, with a mean of 40.4%. Pulmonary infection ranged from 9% to 35.7% of patients, with a mean of 18.8%. Granulation tissue ranged from 7.1% to 64% of patients, with a mean of 24.85%. Stent migration ranged from occuring in 0% to 11.1% of patients, with a mean of 3.25%. There were no reported intraoperative complications during placement of these silicone Y stents (

Table 3. Complications of silicone Y stents as reported in other studies.

Study	Country of Origin	Study Type	Sample Size	Mean Age	Indication for Placement	Mucus Plugging (%)	Infection (%)	Granulation Tissue (%)	Stent Migration (%)
Agarwal, et al. [6]	India	Multicenter Systematic Review	27	57.7	CAO (77.8%), TE fistulae (29.6%)	25.9%	Data not collected	14.8%	3.7%
Zeng, et al. [18]	China	Single Center Retrospective Analysis	17	57.7	BP Fistulae	“Common”—data not quantified	11.8%	11.8%	5.8%
Wang, et al. [19]	China	Single Center Retrospective Analysis	10	68.3	TE Fistulae	60%	“Reported”—data not quantified	30%	0.0%
Aktaş, et al. [20]	Turkey	Single Center Retrospective Analysis	46	63.2	CAO	8.7%	Data not collected	13%	2.2%
Nam, et al. [21]	Korea	Single Center Retrospective Analysis	11	48	Benign carinal stenosis	18%	9%	64%	0.0%
Zeng, et al. [22]	China	Single Center Retrospective Analysis	14	58.5	Massive hemoptysis due to malignancy (71.4%) or benign processes (28.6%)	64.3%	35.7%	7.1%	0.0%
Ozgul, et al. [23]	Turkey	Single Center Retrospective Analysis	9	67	COPD wit expiratory central airway collapse	66.67%	Data not collected	33.33%	11.1%

).

4. Discussion

4.1. Comparison of SEM and Silicone Y Stents

In the United States, SEM Y stents are uncommon as the FDA has only just recently approved them in the past few years [16]. Much like silicone Y stents, we observed that SEM Y stents are effective at stenting open the central airway, allowing for decreased oxygen requirements and liberation from mechanical ventilation. As a purely palliative treatment option, it allows patients to discharge to a hospice program or potentially back home/to their facility, if their condition allows. When comparing the complication rates of our SEM Y stent recipients to silicone Y stent recipients, we found similar rates between the two groups. Primarily, rates of mucus plugging were almost identical (42.9% SEM, mean 40.4% silicone). We found our rate of infection to be higher, although comparison was limited as many studies were not tracking infection secondary to stenting (35.7% SEM, mean 18.8% silicone). Although few, there were incidences of stent migration reported with silicone stenting (mean 3.25%) as opposed to our zero incidences. It has been reported that removal of silicone stents is noticeably easier when compared to SEM stents [24]. This greater ease of removal may suggest why migration is more common with silicone stenting. Finally, granulation tissue formation was more commonly reported with silicone stents when compared to our SEM population (14.3% SEM, mean 24.85% silicone). One of the reported benefits to silicone stenting is it flexibility, allowing it to better conform to respiratory anatomy, thus decreasing granulation tissue formation [25]. The differences of the expected outcome and our data could potentially be explained by the relatively short duration of stent placement as most patients discharged to hospice and thus had no follow up (Figure 9).

In a study by Lachkar, et al. at Rouen University Hospital in France comparing outcomes and complications of SEM and silicone Y stents placed in their facility, they found no major difference in outcomes and complications between the two stent types [1]. They noted that the main benefits of SEM stents were ease and speed of placement with lower failure rates when compared to silicone stents. Additionally, a study by Ortiz-Comino found no statistically significant increase in complications with SEM when compared to silicone Y stents [15]. The data from these studies is reassuring for our data, given then theirs are from single centers.

4.2. Study Limitations

This study has many limitations, primarily because it is a single center retrospective study with a small sample size. The small sample size and rarity of the disease process limits its overall generalizability. Additionally, being a community hospital, academic resources are limited when compared to larger academic centers. Another limitation is absence of silicone stent data at our hospital, thus not allowing for any statistical comparisons, solely relying on observations. Regarding our data on oxygen needs, we used oxygen saturation and supplemental oxygen requirements, but did not have pre- and post-stenting arterial blood gasses to better assess for improvement in oxygenation and ventilation.

5. Conclusions

When comparing SEM and silicone Y stents in terms of efficacy and side effect profiles, we found them to be very similar. Despite the limitations of our study and overall scarcity of data available in literature, we remain optimistic about the future of the expanded role of SEM stents. Both silicone and SEM stents have their benefits and drawbacks, but when taking into consideration the patient population in comparison studies, moribund patients with advanced malignancy, the drawbacks of SEM stents causing more damage upon removal is less of a factor. SEM Y stents are an effective alternative to silicone Y stents in patients with malignant airway disease that can be easily and effectively implemented in a community hospital. The lack of necessity for rigid bronchoscopy improves the speed and technical difficulty of the stenting procedure, thus making SEM stents more desirable when compared to silicone. As physicians in the USA become more comfortable and aware of SEM stents, it is possible that soon, they become the first line stent for malignant CAO and leaving silicone stents for benign CAO.