Expiratory central airway collapse (ECAC) is defined as abnormal central airway narrowing during expiration.1 Under the definition of ECAC, there are 2 main subgroups. The first group is tracheobronchomalacia (TBM) where, the cartilaginous structures are weak and leads to airway collapse. The second group is excessive dynamic airway collapse (EDAC) where, posterior membranous part of central airways bulges into airway lumen during expiration.1
There are various classifications for TBM. According to etiology, TBM is divided into as congenital (primary) and acquired (secondary) TBM.2 Another classification is according to the severity of malacia with lumen narrowing below 50% is considered to be normal, 50% to 75% is mild, 75% to 90% is moderate, and >90% is severe malacia.3 Afterwards, this classification was found insufficient, and multidimensional classification system Functional status, Extent, Morphology, Origin of the airway abnormality, Severity of airway collapse (FEMOS) was developed.4 FEMOS classification system was based on functional status (F), extent (E), and severity (S) of airway collapse as well as the morphology (M) and origin (O) of the airway abnormality.4
The combined prevalence of TBM and EDAC was reported 4% to 23% in bronchoscopy for various indications.5 In patients with chronic obstructive pulmonary disease (COPD), ECAC prevalence was found 12.7% and 23% by Ikeda et al3 and Jokinen et al,6 respectively. However, these studies are very old and they did not evaluate TBM and EDAC separately. Although there is no data on TBM prevalence in COPD according to current classification, a study reported 22% EDAC prevalence in patients with asthma and COPD.7 However, there is no proven correlation among any pulmonary function parameter related to COPD severity and tracheal collapse.8 In addition, expiratory tracheal collapse has been more frequently observed in patients with COPD and morbid obesity.9 Of 8820 patients, 443 (5%) of them have found to be ECAC, in a cohort study based on computerized tomography (CT) reported by Bhatt et al.10 In the same study, compared with control group, ECAC group reported to have statistically significantly higher pack years smoking and COPD. Patients with ECAC, compared with control group, had worse St George’s Respiratory Questionnaire scores and modified Medical Research Council (mMRC) scale scores, but no significant difference in 6-min walk distance.10 TBM causes symptoms of exertional dyspnea, difficulty in expectorating secretion, and chronic cough.11 There are studies reporting that presence of TBM might be related with frequent exacerbations of COPD resulting in hospitalization.12
Bronchoscopy is considered the gold standard for diagnosis of TBM. A maneuver is needed to see the tracheobronchial collapse, but this maneuver has not been standardized.13 TBM is reported in 1% of routine bronchoscopy. Although the use of dynamic CT in the diagnosis of TBM is reported,14 recent studies showed that 70% to 80% of normal population also met diagnostic criteria of 50% cutoff of airway collapse in dynamic CT.15
The recommended treatment options for TBM are continuous positive airway pressure device (CPAP), tracheobronchoplasty, and silicone stent implantation.13,16,17 However, there is no treatment consensus among these options. Previous studies showed that respiratory symptoms, quality of life, and functional status were improved, in silicone stent implanted patients due to ECAC, in the short term.13,18 Aim of this study is to share the results of silicone stenting for ECAC among patients with severe COPD.
PATIENTS AND METHODS
We evaluated data of 9 patients with stent implantation between December 2010 and November 2014. The data related to treatment and follow-up were collected, retrospectively. Medical history, demographics, radiographic images, digital photos, and videos from bronchoscopic procedures were obtained from the hospital archive. Patients were also called by phone and questioned for the current functional state and mMRC score. We could not obtain extent of abnormality and severity of airway collapse (used in the FEMOS classification of patients) as our archive have no data related to them.4
All patients that had COPD and ECAC were diagnosed via flexible bronchoscopy (Olympus Medical Systems, Tokyo, Japan) which was performed during stable state of the patients. There were various indications for bronchoscopy (such as frequent exacerbations leading hospitalization or poorly controlled symptoms under optimal COPD treatment). We did not use a special maneuver for the diagnosis during flexible bronchoscopy. On the basis of clinical, radiographic, and bronchoscopic evaluation, no other cause beside TBM could be identified for the frequent hospitalization and poorly controlled COPD symptoms. The patients were informed about stent implantation and informed consent form, for the procedure, was obtained. Only 2 of 9 patients have bronchoscopic video, but not the remaining 7. We are sure that all the cases were TBM. Because we performed bronchoscopy ourselves and made the decision according to the definition above. We have bronchoscopy reports of all patients. None of the patients have dynamic CT imaging. Therefore, we would like to write it as ECAC.
Pulmonary function tests were performed using Jaeger Master Screen Pneumo (Jaeger Co., Hoechberg, Germany). The results of the pulmonary function test and mMRC scores were recorded from patient files.
Stent placement was performed in patients with ECAC. No information was obtained about extent of malacia during retrospective data collection. The severity of TBM’s was classified according to the previously described criteria.3 Silicone stenting was performed after discussing situation of patients in a council, made up of thoracic surgeons and chest physicians, and deciding that they were not suitable for tracheobronchoplasty (Fig. 1; Video 1, Supplemental Digital Content 1, http://links.lww.com/LBR/A138; and Video 2, Supplemental Digital Content 2, http://links.lww.com/LBR/A139). The council preferred stent placement in patients who have severe COPD and/or having long segment with malacia, or being unsuitable for surgery due to poor medical condition. No specific phenotype was selected.
Stent placement was performed in the operating room under general anesthesia via rigid bronchoscopy (Karl Storz Instruments, Germany). General anesthesia was composed of total intravenous anesthesia and the patients were ventilated with air-oxygen mixture. After stent deployment, patients were discharged with recommendations to perform nebulizations with isotonic sodium chloride 4 times a day in addition to current COPD treatment. One patient died as an outpatient after stenting due to unknown reasons and 1 patient’s stent was removed due to stent migration. These 2 patients were not included in the statistical analysis. Three months after stent placement, we performed pulmonary function test and evaluated the mMRC score in 7 of 9 patients.
The local ethics committee approval was obtained for the study.
All variables were tested for normality of distribution using the Kolmogorov-Smirnov test. Continuous variables were expressed as mean±SD or median according to distribution state. Categorical variables were presented as total number and percentage. Differences between the groups were assessed using independent samples t test or Mann-Whitney U test for continuous variables, and χ2 test or the Fisher exact test for categorical variables. To determine presence of statistically significant difference among prevalue and postvalue of forced expiratory volume (FEV) 1, forced vital capacity (FVC), and mMRC, we used paired samples t test. P<0.05 was accepted as statistically significant (SPSS 17.0; SPSS Inc., Chicago, IL).
Nine patients were enrolled in this study. Among those, 7 were male. The mean age was 67±10.73 years. The mean follow-up duration was 25.75±13.1 months. Body mass index, FEV1, FEV1% predicted, FEV1/FVC, and FVC of the 9 patients, before Y-stent implantation, were 31.75±3.75, 1.09±0.61, 45.65±20.23, 45.66±20.23, and 1.78±0.5 L, respectively.
We were able to approach 7 of the 9 patients for follow-up pulmonary function test results (1 of them died, due to unknown etiology, after a month of stenting procedure and another one had stent migration 2 days later of stenting procedure). Consequently, comparisons before and after stenting were made on the available 7 patients. The change in FEV1 (before and after stenting) was 0.02±0.08 L and it was not statistically significant (P=0.51). The mean mMRC score were 3.12±0.69 and 2.57±0.53 for before and after stenting, respectively. This improvement was statistically significant (P=0.03) (Table 1). The improvement in functional state of the patients were given in Table 2.
In 1 case, there was malacia only at the left and right main bronchi. Two of the patients had tracheal malacia only, whereas the rest of 6 patients had malacia at the trachea and main bronchi. One patient needed short-term CPAP after Y-stent placement.
The patients needed recurrent bronchoscopy during follow-up due to high rate complications. Detailed information about the complications during follow-up were given in detail in Table 2. The mean number of bronchoscopies were 2.2 times (Table 2).
According to our best knowledge, there are very few study on stent placement for TBM associated with severe COPD.13,19 The study showed that stent placement can be performed under general anesthesia via rigid bronchoscopy safely in severe COPD complicated with ECAC. We observed that functional status and mMRC scale improved after stenting. However, we frequently encountered complications in short and long follow-up terms.
The pathophysiology and etiology of ECAC are not known exactly.19 It is known that ECAC frequently accompanies chronic pulmonary diseases such as chronic bronchitis and emphysema.5,10,19 Smoking, which is the most important cause of COPD, causes chronic irritation and inflammation. Furthermore, it has also been reported to be the reason of ECAC.20,21
The gold standard method to diagnose TBM is bronchoscopy.11 Although some studies reported that dynamic CT could be used to diagnose TBM,22 other studies proved that airway collapse in dynamic CT might be seen in healthy volunteers as well.15 A study based on CT reported the prevalence of central airway malacia up to 53% in patients with COPD.23 In addition, EDAC were reported more frequently in patients with COPD and morbid obesity.9,10 In our study, the mean body mass index of our 9 patients was 31.75±3.75, which was compatible with the literature. Although COPD being the fourth most common cause of death today, it is estimated to rise to the third place in 2020.24 The frequency of exacerbations, hospitalization, and mortality due to COPD increase with the presence of TBM. It has been reported that TBM may be a risk factor for COPD exacerbation. In the same study, it has been highlighted that the COPD patients with TBM requires hospitalization 2-fold compared with COPD only.12 In addition, the airway stabilization, carried out in patients with TBM was reported to be useful.13 Our reason to perform bronchoscopy was uncontrolled COPD symptoms under optimal treatment conditions. Improvement of the patients’ functional status and mMRC scores after stent placement, in our study, is compatible with literature.
Stent-related complications (such as migration, mucus plugging, granulation tissue, infection, and airway perforation) are well described in the literature.5 In addition, silicone Y-stent application for TBM is known to cause the same frequent complications.13
The results of our case series showed that stent-related complications are more frequently encountered during the follow-up period. In contrast, no serious complication was observed during silicone Y-stent placement for ECAC with severe COPD. Therefore, it requires close monitoring of the patients. In one of our cases, a stent was oversized and replaced with a smaller one. Subsequently the stent migrated at the early stages and removed. One patient died due to an unknown reason 1 month later of the stent placement outside the hospital. For the remaining 7 patients, we needed to perform recurrent bronchoscopic interventions, for follow-up and complications, with mean number of 2.2 times, which was consistent with previously reported complication rates.13 Murgu and Colt18 reported that their patients got rapid symptomatic relief after silicone stenting due to ECAC. However, they also experienced frequent stent-related complications, and needed recurrent bronchoscopic interventions.
Our study had limitations. As it is a retrospective-uncontrolled case series, we were not able to obtain data related to current TBM classification. Further, we could not compare our method with CPAP and tracheobronchoplasty.
In conclusion, there were 2 different observations in terms of the conditions of the patients with the stent placement. On the one hand, there was frequent stent-related complications during the follow-up period for ECAC in the patients with severe COPD. These frequent complications may be listed as the stent migration, stent obstruction with secretion, and granulation tissue formation. In contrast, these patients had rapid improvement in their functional state and dyspnea score after the stent implantation, and there was no serious complication during the stent placement. The patients had rapid improvement in functional state and dyspnea score after stent implantation. Consequently, prospective and controlled studies are warranted to elucidate different treatment methods in ECAC with COPD.
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