Pulmonary Function Improves After Expandable Metal Stent Placement for Benign Airway Obstruction

Pulmonary Function Improves After Expandable Metal Stent Placement for Benign Airway Obstruction* Mark D. Eisner, MD; Roy L. Gordon, MD; W. Richard Webb, MD; Warren M. Gold, MD; Sameer E. Hilal, BA; Keith Edinburgh, MD; and Jeffrey A. Golden, MD

Study objective: To determine whether expandable metal stent placement for benign airway lesions improves pulmonary function. Design: Case series. Setting: University medical center. Patients: Nine patients who underwent balloon-mediated expandable metal stent deployment for airway obstruction due to benign etiologies. Results: All nine patients had expandable stents deployed for benign airway lesions using fiberoptic bronchoscopy and fluoroscopic guidance. Pulmonary function improved after stent placement. The mean FVC increased by 388 mL (95% confidence interval [CI], 30 to 740 mL), the mean peak expiratory flow (PEF) increased by 1,288 mL (95% CI, 730 to 1,840 mL), the mean FEV1 increased by 550 mL (95% CI, 240 to 860 mL), and the mean forced expiratory flow between 25% and 50% of vital capacity (FEF25–75%) increased by 600 mL (95% CI, 110 to 1,090 mL). Corresponding relative measurements included increases in FVC (12%), PEF (95%), FEV1 (38%), and FEF25–75% (87%). The complete characterization of a benign airway obstruction generally required a multimodal approach. Conclusions: Expandable metal stent placement appears to be an effective therapy for benign airway obstruction. (CHEST 1999; 115:1006 –1011) Key words: airway obstruction, surgery; bronchial diseases, therapy; bronchoscopy; forced expiratory volume; stents Abbreviations: CI 5 confidence interval; PEF 5 peak expiratory flow; FEF25–75% 5 forced expiratory flow between 25% and 75% of vital capacity

airway obstruction can result in dyspnea, C entral cough, and impaired clearance of respiratory secretions. A variety of benign etiologies can underly airway obstruction, including tracheomalacia, tracheal stricture, inflammatory diseases such as Wegener’s granulomatosis and relapsing polychondritis, and anastomotic stricture following lung transplantation.1 In benign airway lesions, silicone stents have been used successfully to relieve obstruction.2–7 *From the Division of Pulmonary and Critical Care Medicine, Department of Medicine (Drs. Eisner, Gold, and Golden), the Cardiovascular Research Institute (Drs. Eisner, Gold, and Mr. Hilal), the Section of Interventional Radiology (Dr. Gordon), and the Department of Radiology (Drs. Webb and Edinburgh), University of California, San Francisco, CA. Supported by National Research Service Award T32 HL07185 (Dr. Eisner). Manuscript received June 25, 1998; revision accepted November 2, 1998. Correspondence to: Mark D. Eisner MD, Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, 350 Parnassus Ave, Suite 609, San Francisco, CA 941430924; e-mail: [email protected] 1006

More recently, expandable metal stents have been deployed in patients with tracheobronchial obstruction.8 –26 Expandable stents, such as Gianturco (Cook Cardiology Inc; Bloomington, IN), Palmaz (Johnson and Johnson; Warren, NJ), and Wallstents (Pfizer; New York, NY), have several advantages over silicone stents. Expandable stents can be placed by fiberoptic (vs rigid) bronchoscopy using fluoroscopic guidance.22–25 Metal stents become epithelialized, potentially improving mucociliary clearance.26 In addition, these stents can be placed more distally in the tracheobronchial tree using fiberoptic bronchoscopy, thus avoiding the occlusion of main branch airways. Compared to silicone stents, metal stents have a larger internal-to-external diameter ratio and are less likely to migrate.22–26 The goal of stent placement is to relieve airflow obstruction. The physiologic impact of silicone stents has been well characterized, with improvements in FVC, FEV1, and forced expiratory flow between 25% and 50% of vital capacity (FEF25–75%).27–29 Clinical Investigations

Likewise, pulmonary function testing after expandable metal stent placement for endobronchial carcinoma has revealed improved expiratory airflow.22,25,30 However, the effect of expandable metal stent deployment on pulmonary function in benign airway obstruction is less certain. Two studies23–24 reported an improvement of FEV1 following expandable stent placement for benign disease. A further characterization of the postprocedure pulmonary function was not provided. In this report, we analyze the impact of expandable metal stent placement on pulmonary function in a retrospective case series of patients with benign airway lesions.

bronchoscope and across the airway lesion. The bronchoscope was then removed, leaving the wire in position. The stent was then placed over the wire using standard coaxial techniques. Fluoroscopy was used first to position the stent and then to facilitate the balloon dilatation of the stent. Using balloon inflation, the stents were dilated to restore the normal airway diameter. The bronchoscope was reinserted, and the stent position was confirmed by direct visual inspection. If necessary, fine-tuning of the stent position was carried out under fluoroscopic and bronchoscopic guidance. Maneuvers such as further dilatation, additional stent placement, and stent manipulation were then performed. Our goal was to maintain a normal airway diameter without occluding the side branches with the stent. The goal was eventual epithelialization of stent struts. Periprocedure antiobiotics or steroids were not routinely utilized. To compare the pulmonary function before and after stent placement, a 2-tailed paired t test was used and 95% confidence intervals (CIs) were constructed.

Materials and Methods We deployed expandable metal stents in nine patients with benign tracheal or bronchial stenosis. All of the patients were symptomatic and had moderate to severe dyspnea. The patients underwent physiologic, radiologic, and bronchoscopic evaluation before and after stent placement. Eight patients had spirometry performed (Collins Cybermedic; Braintree, MA) using a standard protocol conforming to the guidelines of the American Thoracic Society.31 The FVC, peak expiratory flow (PEF), FEV1, and FEF25–75% were determined. In addition, the flow-volume loop contours were studied. Patient 9 had a tracheostomy and could not undergo spirometry. All of the patients underwent thoracic CT scanning. Dynamic inspiratory and expiratory images were obtained to further characterize the location and degree of the airway obstruction. Every patient underwent fiberoptic bronchoscopy to directly visualize the airway stenosis. Informed consent was obtained prior to all procedures. To minimize discomfort, stent placement was performed under general anesthesia in all patients. After endotracheal intubation, fiberoptic bronchoscopy was performed to precisely localize the site of obstruction. The bronchoscopic visualization of the endobronchial obstruction was correlated with preoperative thoracic CT scan images and real-time fluoroscopic imaging. Using CT, fluoroscopy, and bronchoscopy data, the length and diameter of the lesion was determined. A guidewire was passed down the

Results The mean age (6 SD) was 53.7 6 10.2 years old (range, 34 to 66 years old; Table 1). There were five men and four women. Five patients had anastomotic strictures after lung transplantation. In addition, patient 5 had an extrinsic compression of his left mainstem bronchus by enlarged thoracic lymph nodes infiltrated with amyloid. Inflammatory airway disease was caused by Wegener’s granulomatosis in one patient, by relapsing polychondritis in another patient, and by idiopathic tracheobronchial stenosis in a third patient. Patient 4 had severe emphysema, with dynamic expiratory collapse of the intrathoracic trachea demonstrated by both CT scanning and bronchoscopy. Figure 1 demonstrates improved spirometry after expandable metal stent placement. The mean FVC increased by 388 mL (95% CI, 30 to 740 mL), the mean PEF increased by 1,288 mL (95% CI, 730 to

Table 1—Patient Characteristics* Patient/Age, yr/ Gender 1/57/F 2/34/F 3/44/M 4/65/M 5/60/M 6/53/F 7/66/M 8/49/M 9/55/F

Diagnosis Lung transplant (emphysema) AIDS, idiopathic tracheobronchial stenosis Relapsing polychondritis Emphysema Lung transplant (amyloidosis) Lung transplant (emphysema) Lung transplant (primary pulmonary hypertension) Lung transplant (a1-antitrypsin deficiency) Wegener’s granulomatosis

Site of Obstruction

Stent Type

Stent Size

FEV1 (L/s) (pre-stent)

FEV1 (L/s) (post-stent)

L MSB anastamosis Trachea, L MSB Trachea, R and L MSB Trachea L MSB R MSB anastamosis L MSB anastamosis

Palmaz Palmaz Palmaz Wallstent Palmaz Palmaz Wallstent

10 3 30 mm† 9 3 30 mm 8 3 30 mm 24 3 35 mm 9 3 30 mm 8 3 20 mm 8 3 20 mm

0.8 1.9 1.6 1.4 0.7 2.1 2.6

1.2 3.0 1.7 2.0 1.8 2.3 2.9

R MSB

Wallstent

10 3 20 mm

1.5

1.7

L MSB

Palmaz

9 3 30 mm

NA‡

NA

*F 5 female; M 5 male; L 5 left; R 5 right; MSB 5 mainstem bronchus; NA 5 data not available. †Stent size given as diameter 3 length (mm). ‡Spirometry not performed due to tracheostomy. CHEST / 115 / 4 / APRIL, 1999

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Figure 1. Pulmonary function before and after expandable metal stent placement. The bar graph depicts the average of each pulmonary function parameter before and after stent deployment.

1,840 mL), the mean FEV1 increased by 550 mL (95% CI, 240 to 860 mL), and the mean FEF25–75% increased by 600 mL (95% CI, 110 to 1,090 mL). The corresponding relative measurements included increases in FVC (12%), PEF (95%), FEV1 (38%), and FEF25–75% (87%). In addition, the FEV1/FVC ratio improved by 130 mL (95% CI, 0 to 260 mL), a 28% improvement. Flow-volume loop contours also improved after stent placement. In Figure 2, the preprocedure flow-volume loop (patient 5) demonstrated markedly diminished expiratory flows with a plateau appearance. After stent placement, the flow-volume loop reveals increased flows and a near-normalization of the contour. In all cases, follow-up bronchoscopy confirmed an improvement in airway diameter immediately following stent placement. In most cases, a multimodal evaluation was necessary to fully characterize the patient’s suitability for stent placement. Patient 6, for example, had undergone left single-lung transplantation for severe emphysema. He had a preprocedure flow-volume loop demonstrating decreased expiratory flows at midlung volumes and a reduced vital capacity (Fig 3).

Given the patient’s extremely poor native lung function, we expected the right mainstem bronchus to function as the main conduit for air flow. As a result, the obstruction of the right mainstem bronchus anastomosis would produce an expiratory plateau typically seen with supracarinal intrathoracic airway obstruction. There is, however, no clear plateau to suggest such an obstruction. However, dynamic CT scan (Fig 4) and fiberoptic bronchoscopy both confirmed an airway obstruction at the right mainstem bronchial anastomosis. The CT scan demonstrated a long stenotic segment from the anastomosis into the bronchus intermedius. With expiration, the bronchus intermedius completely collapsed, while the proximal right mainstem bronchus narrowed but remained patent. Thus, the right upper lobe bronchus was able to ventilate throughout the respiratory cycle, explaining the absence of a plateau on the flow-volume loop. After stent placement, dynamic CT scanning demonstrated that the bronchus intermedius remained patent throughout the respiratory cycle (Fig 4). After the procedure, one patient developed an acute bronchospasm that responded promptly to nebulized b-agonist therapy. There were no instances of postprocedure hemorrhage, pneumothorax, intubation, or other acute complications. To monitor the clinical adequacy of stent placement, we followed all of the patients longitudinally. The median follow-up duration was 23 months (25th to 75th interquartile; range, 20 to 29 months). In all patients, a follow-up bronchoscopy revealed patent stents with no migration. In eight patients, we observed epithelialization of the stent struts with no granulation tissue or overgrowth. In patient 2, we observed endobronchial granulation tissue similar to what was observed prior to placement of the stent. Repeat stent placement was required in three patients. For patient 3, who had relapsing polychondritis, the placement of a tracheal stent did not

Figure 2. The flow-volume loop before and after expandable metal stent placement. The left panel depicts the preprocedure flow-volume loop (patient 5) that demonstrates markedly diminished expiratory flows and a plateau appearance. After stent placement, the flow-volume loop (right panel) revealed increased flows and a more normal-appearing contour. 1008

Clinical Investigations

Figure 3. The flow-volume loop before and after stent placement in patient 6. Left: the preprocedure flow-volume loop that demonstrates diminished expiratory flows at all lung volumes is shown. No plateau was apparent in the expiratory limb. Right: increased expiratory flows after expandable metal stent placement is shown.

relieve the airway obstruction. Excellent results were achieved after bilateral mainstem bronchial stenting during a second procedure. Patient 5 had amyloidosis, with progressive thoracic lymphadenopathy compressing the left mainstem bronchus. As a result, he required a subsequent left mainstem bronchial stent placement for further extrinsic narrowing. Patient 2 experienced a progression of her underlying inflammatory trachoebronchial process, necessitating a repeat left mainstem bronchial stent placement. Discussion In our series of patients with central airway obstruction from benign lesions, pulmonary function substantially improved after expandable metal stent placement. Dynamic thoracic CT scanning and fiberoptic bronchoscopy confirmed an improved airway diameter in all cases. Our study extends the physiologic observations made previously concerning expandable metal stent placement for malignant endobronchial lesions.22,25,30 Silicone stents, such as the Dumon stent (Bryan Corp; Woburn, MA), have long been used to relieve malignant and benign airway obstructions.1–7 Several reports have demonstrated a physiologic improvement after the placement of a silicone stent. Gelb et al27 described 15 patients who underwent silicone

stent deployment for a variety of benign and malignant etiologies. After stent placement, there were increases in FVC (14%), FEV1 (47%), and FEV1/ FVC (32%). A similar review28 of 24 patients after silicone stent deployment found increases in FVC (9%), PEF (40%), FEV1 (32%), and FEF25–75% (43%). Other reports29 –30 have confirmed that respiratory physiology improves after silicone stenting. Expandable metal stents improve pulmonary physiology in patients with malignant airway lesions. Wilson and colleagues22 reported a series of 56 patients with malignant airway obstruction (47 of whom had bronchogenic carcinoma) who underwent Gianturco stent placement. Improvements were noted in FVC (10%), FEV1 (22%), and PEF (18%). The impact of expandable metal stents on pulmonary function in patients with benign airway lesions has not been well established. Rousseau and colleagues24 placed 74 stents for mostly benign indications and reported the FEV1 for a subset of 16 patients. The FEV1 increased by 38% in 6 patients who received Wallstent prostheses, but there was no improvement in 10 patients who received Gianturco stents. In a study25 of 14 patients with anastomotic strictures after lung transplantation, investigators found a substantial increase in FEV1 (117%) after expandable metal stent placement. In both studies, other spirometric measurements were not reported. Our study extends these observations, demonstrating CHEST / 115 / 4 / APRIL, 1999

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Figure 4. Dynamic thoracic CT scanning before and after expandable metal stent placement. Top, A: the expiratory thoracic CT image demonstrates a near-total collapse of the bronchus intermedius. Interestingly, the herniation of the right lung though a postoperative thoracic wall defect can be seen. Middle, B: inspiratory thoracic CT image after stent placement demonstrating a patent bronchus intermedius. Bottom, C: expiratory CT image after stent placement demonstrating the patency of the bronchus intermedius throughout the respiratory cycle.

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an improvement in all four standard spirometric measurements following the placement of expandable metal stents for benign conditions. Furthermore, we observed hyperplastic overgrowth—a potential problem with metal stents—in only one patient. Since stenting provides an effective treatment for central airway obstruction, the diagnosis of airway lesions becomes important. Traditionally, the flowvolume loop contour has been pivotal in the evaluation of patients with suspected central airway obstruction.27,32–33 The detection of a flow-limiting plateau in either limb of the flow-volume loop suggests an airway obstruction above the carina. A central airway obstruction, however, can sometimes be difficult to detect. Obstruction at multiple sites can produce atypical flow-volume loops, making interpretation difficult.32,34 More commonly, patients with COPD may not manifest typical flowvolume plateaus despite the presence of severe central airway obstruction.34 –37 These patients may be incapable of generating sufficient flows to manifest a flow-limiting plateau, so the expiratory flowvolume limb will manifest decreased flows at all lung volumes and marked curvilinearity indistinguishable from severe COPD.35–37 In such patients, other diagnostic testing may be required to detect airway obstruction. In single-lung transplantation patients, the spirometric detection of an anastomotic bronchial obstruction can also be difficult to achieve. If native lung function is sufficient, it can contribute to the flow-volume loop, and no flow-limiting expiratory plateau occurs. If native lung function is severely impaired, the contralateral mainstem bronchus might function as a single conduit in series with the supracarinal airway. In this instance, an anastomotic obstruction can result in an expiratory plateau. In patient 6, however, the flow-volume loop had no expiratory plateau despite significant anastomotic obstruction and extremely poor native lung function. In this case, dynamic CT scanning demonstrated a long area of airway stenosis from the anastomosis into the bronchus intermedius. With expiration, the distal stenotic segment (in the bronchus intermedius) collapsed, but the proximal right mainstem bronchus remained patent enough to allow right upper lobe ventilation. As a result, no expiratory plateau occurred. Therefore, the detection of anastomotic strictures in single-lung transplant patients often requires a multimodal approach, including spirometry, thoracic CT scanning, and bronchoscopy. There are several limitations to our study. Our sample was a small, highly selected group of patients. As a result, the efficacy of expandable metal stent Clinical Investigations

placement in other benign airway disorders requires further study. Also, repeat stent placement was commonly necessary to maintain a clinical benefit, necessitating a careful clinical follow-up. Finally, this study focuses on the short-term physiologic benefits of expandable metallic stent placement. The impact on longer term clinical outcomes such as quality of life, health care utilization, and mortality remains to be characterized. We have demonstrated that expandable metal stent placement using fiberoptic bronchoscopy and fluoroscopic control improves pulmonary function in patients with benign airway lesions. A multimodal approach is often required to adequately evaluate a benign airway obstruction.

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