Airway stenting in Japan

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.

Assessment of Extensive Airway Obstruction Using Point-by-Point Lateral Pressure Measurements during Bronchoscopy

BACKGROUND

The positioning of the stent at the flow-limiting segment is crucial for patients with extensive airway obstruction to relieve dyspnea. However, CT and flow-volume curves cannot detect the area of maximal obstruction.

OBJECTIVES

The aim of this study is to physiologically evaluate extensive airway obstruction during interventional bronchoscopy.

METHODS

We prospectively measured point-by-point lateral airway pressure (Plat) at multiple points from the lower lobe bronchus to the upper trachea using a double-lumen catheter in 5 patients. The site of maximal obstruction was evaluated continuously to measure point-by-point Plat at multiple points when the airway catheter was withdrawn from the lower lobe bronchus to the upper trachea.

RESULTS

Remarkable pressure differences occurred at the site of maximal obstruction assessed by point-by-point Plat measurements. After initial stenting in 1 case, migration of the maximal obstruction to a nonstented segment of the weakened airway was seen with extensive stenosis from the trachea to the bronchi. In the second case, in addition to radiological analysis, point-by-point Plat measurements could identify the location of the maximal obstruction which contributed to dyspnea.

CONCLUSIONS

Point-by-point Plat measurement could be used to detect the site of maximal obstruction physiologically. Furthermore, Plat measurement could assess the need for additional procedures in real time in patients with extensive airway obstruction.

Assessment of Bronchial Obstruction Using Lateral Pressure Measurement during Bronchoscopy

BACKGROUND

In patients with bronchial obstruction estimating the location of the maximal obstruction is crucial for guiding interventional bronchoscopy. However, flow-volume curves cannot discriminate between the right and left lungs.

OBJECTIVES

The aim of this study was to physiologically evaluate bronchial obstruction during interventional bronchoscopy.

METHODS

We prospectively measured lateral airway pressure (Plat) at either side of the obstruction using a double-lumen catheter (pressure-pressure [P-P] curve) simultaneously to assess the degree of bronchial obstruction in 22 patients. The shape of the P-P curve was assessed to confirm the site of maximal obstruction.

RESULTS

In the experimental study, Plat was uniform between both bronchi in the normal model. For the unilateral and bilateral obstruction models, a phase shift was only seen for the more obstructed side. In healthy subjects, the angle of the P-P curve was close to 45° and linear in shape. In patients with bronchial obstruction, the angle was much smaller but approached 45° after the bronchoscopic procedure. The degree of bronchial obstruction was significantly correlated with the angle of the P-P curve (r = -0.51, p < 0.01). Dyspnea significantly increased when the airway lumen was obstructed by more than 60% (p < 0.0001), and when the P-P curve appeared loop-shaped (p < 0.01).

CONCLUSIONS

The shape of the P-P curve could be used to detect the site of maximal obstruction for the optimal positioning of the stent and assess the need for additional procedures in real time in patients with bronchial obstruction.

Left and right lung asynchrony as a physiological indicator for unilateral bronchial obstruction in interventional bronchoscopy

BACKGROUND

In patients with bronchial obstruction, pulmonary function tests may not change significantly after intervention. The airflow asynchrony in both lungs due to unilateral bronchial obstruction may be applicable as a physiological indicator. The airflow asynchrony is reflected by the difference in the left and right lung sound development at tidal breathing.

OBJECTIVES

To investigate the usefulness of left and right lung asynchrony due to unilateral bronchial obstruction as a physiological indicator for interventional bronchoscopy.

METHODS

Fifty cases with central airway obstruction were classified into three groups: tracheal, bronchial and extensive obstruction. The gap index was defined as the absolute value of the average of gaps between the left and right lung sound intensity peaks for a 12-second duration.

RESULTS

Before interventional bronchoscopy, the gap index was significantly higher in the bronchial (p<0.05) and extensive obstruction groups (p<0.05) than in the tracheal group. The gap index in cases with unilateral bronchial obstruction of at least 80% (0.18±0.04 seconds) was significantly higher than in cases with less than 80% obstruction (0.02±0.01 seconds, p<0.05). After intervention for bronchial obstruction, the dyspnea scale (p<0.001) and gap index significantly improved (p<0.05), although no significant improvements were found in spirometric assessments. The responder rates for dyspnea were 79.3% for gap indexes over 0.06 seconds and 55.6% for gap indexes of 0.06 seconds or under.

CONCLUSIONS

Assessment of left and right lung asynchrony in central airway obstruction with bronchial involvement may provide useful physiological information for interventional bronchoscopy.

Interventional Bronchoscopy in the Management of Airway Stenosis Due to Tracheobronchial Tuberculosis

STUDY OBJECTIVES

To assess the efficacy and complications of interventional bronchoscopic techniques in treating airway stenosis due to tracheobronchial tuberculosis.

DESIGN

Case series.

SETTING

Respiratory care centers at two tertiary care referral teaching hospitals in Japan, Hiroshima City Hospital and Okayama Red Cross Hospital.

PATIENTS AND INTERVENTIONS

A total of 30 patients were admitted to the hospital with a diagnosis of tracheobronchial tuberculosis between January 1991 and January 2002. Of those 11 patients received interventional bronchoscopy, including stent placement, laser photoresection, argon plasma coagulation (APC), balloon dilatation, cryotherapy, and endobronchial ultrasonography (EBUS). One patient with complete bronchial obstruction underwent a left pneumonectomy.

RESULTS

Six patients underwent stent placement after balloon dilatation, while the remaining five patients underwent only balloon dilatation. In six patients, Dumon stents were successfully placed to reestablish the patency of the central airways. Two patients first had Ultraflex stents implanted but had problems with granulation tissue formation and stent deterioration caused by metal fatigue due to chronic coughing. Dumon stents then were placed within the Ultraflex stents after the patient had received treatment with APC and mechanical reaming using the bevel of a rigid bronchoscope. In four patients, EBUS images demonstrated the destruction of bronchial cartilage or the thickening of the bronchial wall. The main complications of Dumon stents are migration and granulation tissue formation, necessitating stent removal, or replacement, and the application of cryotherapy to the granuloma at the edge of the stent.

CONCLUSION

Interventional bronchoscopy should be considered feasible for management of tuberculous tracheobronchial stenosis. Dumon stents seem to be appropriate, since removal or replacement is always possible. Ultraflex stents should not be used in these circumstances because removal is difficult and their long-term safety is uncertain. EBUS could provide useful information in evaluating the condition of the airway wall in cases of tracheobronchial tuberculosis with potential for bronchoscopic intervention.

Stenting at the Flow-limiting Segment in Tracheobronchial Stenosis due to Lung Cancer

Airway stenting at the wave-speed flow-limiting segment (the choke point) is assessed. We determined prospectively the precise location of the choke point using the flow-volume curve, endobronchial ultrasonography, ultrathin bronchoscopy, and three-dimensional computed tomography scan before and after stenting in 64 patients with extrincic compression due to lung cancer. We noted distinct flow-volume curve patterns specific to the type of stenosis. The tracheal stenosis group indicated fixed narrowing patterns with an expiratory plateau, bronchial stenosis group dynamic collapse patterns with an expiratory flow deterioration (choking), carinal stenosis group combined fixed and dynamic patterns, and extensive stenosis group complex patterns containing elements of all the former. After stenting, almost full-function patterns with significant improvement in PEF were observed in all groups (p < 0.01, p < 0.05, p < 0.001, p < 0.01, respectively). In patients with extensive stenosis, implantation of additional stents was required when the choke points were observed to have migrated to the areas of malacia with cartilage destruction by the tumor. Secondary stenting at migrated choke points resulted in a significant improvement in PEF over the initial stenting (p < 0.01). Stenting at the choke point improved expiratory flow limitation by increasing the cross-sectional area, supporting the weakened airway wall and relieving dyspnea.

Role of bronchoscopy in modern medical intensive care unit

This article gives a broad overview of the increasingly important applications of bronchoscopy, flexible (FOB) and rigid (RB), in a modern medical intensive care unit. Special emphasis is made to bronchoscopy use in mechanically ventilated patients. Therapies such as endobronchial stenting and Nd:YAG laser are being used to improve respiratory failure and facilitate weaning from mechanical ventilation. Practical applications of recent advancements in technology (endobronchial stenting, laser therapy, and so forth), the increasing use of rigid bronchoscopy, and the new generation of flexible bronchoscopes like battery bronchoscopes, and ultra-thin bronchoscopes, are also discussed. The risks, potential benefits, complications, and suggested technique of performing bronchoscopy in mechanically ventilated patients are reviewed.

Implantation of ultraflex nitinol stents in malignant tracheobronchial stenoses

STUDY OBJECTIVE

To assess the uncovered Ultraflex nitinol stent (Boston Scientific; Natick, MA) for its efficacy and safety.

DESIGN, SETTING, AND PATIENTS

Between October 1997 and October 1998, we carried out a prospective multicenter study at six hospitals in Japan. Fifty-four Ultraflex stents were inserted in 34 patients with inoperable malignant airway stenosis using a flexible and/or a rigid bronchoscope under fluoroscopic and endoscopic visualization.

MEASUREMENTS AND RESULTS

Clinical, endoscopic examination, and pulmonary function on days 1, 30, and 60 after stent implantation showed improvement. In 19 patients (56%), stent implantation was performed as an emergency procedure because of life-threatening tracheobronchial obstruction. Immediate relief of dyspnea was achieved in 82% of the patients. The dyspnea index improved significantly after implantation (before vs. days 1, 30, and 60; p<0.001). Significant improvements were observed in obstruction of airway diameter (81+/-15% before vs. 14+/-17% on day 1, 12+/-12% on day 30, and 22+/-28% on day 60; p<0.001). Vital capacity (VC), FEV(1), and peak expiratory flow (PEF) increased significantly after stent implantation: before vs immediately after VC (p<0.01), FEV(1) (p<0.001), and PEF (p<0.05). The main complications were tumor ingrowth (24%) and tumor overgrowth (21%). After coagulation with an Nd-YAG laser or argon plasma coagulation, mechanical coring out using the bevel of a rigid bronchoscope was necessary in patients showing tumor ingrowth or overgrowth. Removal and reposition were possible in case of misplacement. There were no problems with migration and retained secretions. The median survival time of patients was 3 months. The 1-year survival rate was 25.4%.

CONCLUSIONS

In this study of the Ultraflex nitinol stent, we have demonstrated that patients were relieved from dyspnea, which contributed to improved quality of life, with minimal complications. This stent can be used safely, even in the subglottic region. Owing to its excellent flexibility and biocompatibility, the stent is also indicated in certain complicated situations, eg, narrow stenosis, hourglass stenosis, curvilinear stenosis, bilateral mainstem bronchial stenoses, and long stenosis of varying diameters.