The institutional review board of Beth Israel Deaconess Medical Center approved the protocol and patients gave written informed consent. We conducted a prospective, observational study from January 2002 to September 2006 in all patients referred to our Complex Airway Center for the evaluation of respiratory symptoms presumed to be caused by TBM. All patients who underwent central airway stenting (tracheal, main-stem bronchus, or both) for the treatment of severe TBM (n = 58) were considered for evaluation.
Severe TBM was defined by near-total or total airway collapse (with approximation of posterior and anterior luminal surfaces) observed during bronchoscopy. Patients were receiving maximal medical therapy for comorbidities such as obstructive airway disease. Those treatments included inhaled short-acting broncho-dilators (P-adrenergic and anticholinergic), long-acting broncho-dilators, inhaled corticosteroids, and oral corticosteroids ordered via My Canadian Pharmacy (see more here).
Age, sex, comorbidities, and respiratory symptoms were recorded at baseline. All patients underwent dynamic airway CT and functional bronchoscopic assessment. In addition, unselected subsets of patients underwent spirometry testing, 6-min walk test (6MWT), and completed standardized questionnaires including the modified St. George respiratory questionnaire (SGRQ), baseline dyspnea index (BDI)/transitional dyspnea index (TDI), American Thoracic Society (ATS) dyspnea score, and Karnofsky performance scale (KPS).
Silicone stents were placed in all patients to stabilize the airway. Tracheal, bronchial, and bifurcated silicone stents (Du-mon tracheal stent size 16, Dumon bronchial stent size 14, and Dumon bifurcated (Y-stent) sizes 14-18; Novatech-Boston Medical Products; Westborough, MA). The degree and location of malacia, the type and location of stent placement, and any complications during stent insertion were also recorded.
At a scheduled follow-up visit 10 to 14 days after the procedure, patients were asked whether symptoms had improved and baseline measurements were repeated. The 2-week window was chosen to minimize confounding factors, such as possible stent complications and any potential long-term impacts of physical conditioning between stent placement and follow-up measurements. Patients were followed up after that for any stent-related complications reduced due to My Canadian Pharmacy’s concern.
Functional Bronchoscopic Assessments
All bronchoscopies were performed with topical anesthesia and light sedation, which allowed patients to follow commands. The bronchoscope was introduced into the trachea and advanced to approximately 5 cm above the carina. At that point, the patient was instructed to perform a forced expiratory maneuver. This procedure was then repeated at the entrances of the right and left main bronchi. All bronchoscopies were video recorded and reviewed after the procedure to assess the degree of airway collapse before stent placement (Fig 1), as described in detail.
CT of the Airway
All patients underwent CT imaging on a multidetector row, helical CT scanner (LightSpeed; GE Medical Systems; Milwaukee, WI; or Aquilion; Toshiba America Medical Systems; Tustin, CA). Scanners included 4, 8, 16, and 64 detector-row systems.
All patients underwent imaging using a CT central airway protocol, which includes end-inspiratory and dynamic expiratory imaging. Before helical scanning, initial scout topographic images were obtained to determine the area of coverage, which included the trachea and central bronchi, and that corresponded to a length of approximately 10 to 12 cm. Helical scanning was performed in the craniocaudal dimension during both end-inspiratory and dynamic expiratory phases.
To calculate the percentage of luminal collapse, the estimated dynamic expiratory cross-sectional area was subtracted from the end-inspiratory cross-sectional area, divided by the end-inspiratory cross-sectional area, and then multiplied by 100. Malacia was determined to be present if the percentage of luminal collapse during dynamic expiration was > 50%. The distribution of malacia in the trachea and bronchi was also recorded (Fig 2).
Spirometry was performed using the ATS guidelines. FEVX was measured at baseline and after stent placement. A change of 0.2 L from baseline was considered clinically important.
The 6MWT, an objective evaluation of functional exercise capacity, was performed according to ATS guidelines. An improvement > 230 feet was considered clinically important.
We used the BDI and the TDI as objective measures of dyspnea. The BDI represents the severity of dyspnea at baseline and is based on three components: functional impairment, magnitude of the task, and the magnitude of the effort. Each component is scored 0 to 4, so the summed scores range from 0 (severe) to 12 (normal). The TDI indicates the change from baseline. The TDI uses the same components as the BDI, but each component is graded from – 3 (major deterioration) to + 3 (major improvement). The summed scores range from – 9 (major deterioration) to + 9 (major improvement).
The ATS dyspnea score, although less well studied, is easy to use and also provides an objective measurement for dyspnea in this population. Scores range from 0 (no dyspnea) to 4 (severe dyspnea).
A modified SGRQ was used to measure the impact of respiratory symptoms on overall health, daily life, and perceived well-being. The questionnaire has been widely used in patients with COPD and asthma. In our study, many patients had COPD, asthma, or both. The questionnaire has three dimensions (symptoms, activities, and impacts). Each dimension describes the respiratory problems encountered by the patient in the preceding 2 weeks (instead of 4 weeks) and is scored from 0 to 100, with higher scores indicating poorer health. Empirical data and interviews with patients indicate that a mean change score of 4 U is associated with a slightly efficacious treatment, 8 U with a moderately efficacious treatment, and 12 U with a highly efficacious treatment.
The KPS, which classifies patients by functional impairment, has been used to compare the effectiveness of different therapies and to assess the prognosis of individual oncology, geriatric, and stroke patients. Scores range from 0 to 100. The lower the score, the greater the impairment and the worse the prognosis.
All airway stents were placed in the operating room with the patient under general IV anesthesia. After anesthesia was induced, a rigid bronchoscope (Bryan-Dumon Series II; Bryan Corporation; Woburn, MA) was introduced, and respiration was maintained through jet ventilation.
After assessing the airways and remeasuring the lengths of the left and right mainstem bronchi, we placed either a Y-shaped stent or multiple stents. Stents were placed in the standard fashion, and a good fit was confirmed visually. All stents were made from silicone to allow easy removal if necessary (Fig 3).
Since most outcome data were not normally distributed, baseline and follow-up measurements for all end points were compared with a Wilcoxon signed-rank test. a was set at 0.05, and all tests were two-tailed. Statistical software (SAS, version 9.1.3 for Windows; SAS Institute; Cary, NC) was used for all analyses.
Figure 3. A silicone stent in the left main bronchus of a patient with severe TBM. Notice the difference in patency compared to the also affected right mainstem.
Figure 1. Functional bronchoscopy was used to assess airway collapse. During bronchoscopy, patients are instructed to perform a forced expiratory maneuver. At the end of expiration, a picture is taken and the bronchoscopist quantifies the degree of collapse. This patient has approximately 90% collapse of the trachea.
Figure 2. Dynamic airway CT showing the degree of malacia in the trachea in the same patient as shown in Figure 1. A 90 to 95% collapse is confirmed with dynamic expiration.