Silicone Stent Insertion for Focal Crescent–Type Tracheomalacia in a Patient with Sarcoidosis

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Chapter 11 Silicone Stent Insertion for Focal Crescent–Type Tracheomalacia in a Patient with Sarcoidosis

This chapter emphasizes the following elements of the Four Box Approach: physical examination, complementary tests, and functional status assessment; patient’s support system (also includes family); anesthesia and other perioperative care; and follow-up tests, visits, and procedures.

Case Description

A 62-year-old man with a history of pulmonary sarcoidosis diagnosed 10 years earlier presented with chronic cough and inability to clear secretions. He described his cough as “seal barking.” He had also noted increasing dyspnea with normal physical activities. For the past month, his primary care physician had treated him with short- and long-acting bronchodilators, as well as inhaled and systemic steroids (prednisone 20 mg/day) for suspected adult-onset asthma. He was a nonsmoker, worked as an electrician, and had a history of hypertension and supraventricular tachycardia controlled by diltiazem. Electrocardiogram (ECG) and two-dimensional (2D) echocardiogram were unremarkable. Pulmonary function testing (PFT) revealed moderate obstructive ventilatory impairment without improvement after bronchodilators. Flow volume loop (FVL) showed an airway collapse pattern on the expiratory curve (Figure 11-1). Paired inspiratory/expiratory dynamic computed tomography showed bilateral upper lobe fibrosis, tracheomegaly, and localized narrowing of the lower trachea during dynamic expiration (see Figure 11-1). Flexible bronchoscopy revealed fibrotic closure of the right and left upper lobar bronchi and complete expiratory collapse of the anterior cartilaginous structures in the lower trachea, giving the airway lumen the shape of a crescent (see Figure 11-1).

Figure 11-1 A, Flow-volume loop shows a sudden drop in expiratory flow followed by a plateau phase; these findings characterize the “airway collapse” pattern. B, Paired inspiratory/expiratory computed tomography shows complete collapse of the lower trachea during expiration. C, Dynamic bronchoscopy reveals similar findings and confirms that the collapse is caused by flattening of the anterior tracheal wall, which characterizes the crescent type of tracheomalacia.

Discussion Points

1. Describe five criteria used in classifying expiratory central airway collapse.

2. List three imaging modalities used to diagnose expiratory central airway collapse.

3. List three indications for treatment in this patient.

Case Resolution

Initial Evaluations

Physical Examination, Complementary Tests, and Functional Status Assessment

This patient presented with dyspnea, cough, and mucus retention. These nonspecific symptoms of pulmonary disorders are seen primarily in patients suffering from asthma, chronic obstructive pulmonary disorder (COPD), or bronchiectasis. His cough, however, was described as “seal barking.” This pattern is suggestive of expiratory central airway collapse (ECAC) and presumably is caused by vibration of the floppy membranous posterior wall against the anterior airway wall during expiration.¹ As in our patient, symptoms are usually refractory to corticosteroids and bronchodilators.² In addition, patients with ECAC may have recurrent bronchitis, pneumonia, and even respiratory failure.³ Some patients experience cough-syncope, presumably as a result of a significant rise in intrathoracic pressure and a sudden drop in venous return and cardiac output⁴ during violent coughing episodes.

Spirometry showed obstructive ventilatory impairment. In ECAC, spirometry usually demonstrates obstruction that is proportionate to the severity of the disease.⁵ The expiratory FVL seen in this patient suggested compression of the central airways (see Figure 11-1). This “airway collapse” pattern occurs when maximal flow is quickly reached after expiration of a small volume of air. Following maximal flow, a large fall in flow occurs, although only a small volume is exhaled. Subsequently, the flow rate falls very little during the remainder of expiration. This phase is responsible for the long plateau seen on the FVL (see Figure 11-1).⁶ However, the FVL is neither sensitive nor specific; it can be seen in almost 40% of patients with severe COPD.⁷ Flow oscillations on the FVL have also been described. These take on a sawtooth appearance, defined as a reproducible sequence of alternating decelerations and accelerations of flow. This pattern is nonspecific because it can be seen in patients with obstructive sleep apnea, structural or functional disorders of the upper airway, and neuromuscular diseases.⁸ Lack of clinical and spirometric improvement after bronchodilator administration might be explained by the effects of bronchodilators on central airways. Bronchodilators cause smooth muscle relaxation, further decreasing tracheobronchial wall stiffness and worsening airway obstruction. Bronchodilators increase airway wall compliance. The resulting increased airway compressibility will cause the choke point to be localized to a point closer to the thoracic outlet. The increased length of the upstream segment (from the alveoli to the choke point) and the decreased cross-sectional area at the choke point offset any advantages gained by bronchodilator-induced caliber increase in upstream airways with respect to maximal expiratory flow.⁹ In fact, although this effect has not been studied in adults, a dramatic fall in peak flow in response to bronchodilators has been described in pediatric cases of tracheobronchomalacia (TBM).¹⁰ *

In our patient, a diagnosis of expiratory central airway collapse was made bronchoscopically and on paired dynamic inspiratory/expiratory computed tomography (CT) scanning. Because of the obvious weakness of the lower anterior tracheal cartilaginous wall, this patient had focal crescent tracheomalacia.¹¹ The disorder was characterized by a severe (100%) degree of airway narrowing. During dynamic (functional) bronchoscopy, the airways were visualized by moving the patient into supine, upright, and lateral decubitus positions during spontaneous breathing, as well as during cough, forced expiration, and deep inspiration. During these bronchoscopic assessments, changes in airway lumen can be measured and the extent of collapse noted, and narrowing can be classified as being of the crescent, saber-sheath, or circumferential type. Regions of cartilaginous weakness (tracheomalacia) can be differentiated from areas of excessive dynamic airway collapse (EDAC) or normal physiologic dynamic airway collapse (DAC) (Figure 11-2).

Figure 11-2 A, Normal dynamic airway collapse characterized by bulging of the posterior membrane inside the airway lumen. The cartilage is intact, and airway narrowing during expiration (bottom) is less than 50% as compared with inspiration (top). B, Excessive dynamic airway collapse is caused by excessive bulging of the posterior membrane, which leads to greater than 50% reduction in the airway lumen during expiration. C, In crescent-type tracheomalacia, airway collapse is caused by weakness of the anterior wall, which leads to airway narrowing during expiration.

Among radiologic studies, fluoroscopy was used to diagnose tracheomalacia in the past. During fluoroscopy, one can visualize the airway collapse, but it is difficult to appreciate whether it is due to softening of the cartilage or to excessive bulging of the posterior membrane (Figure 11-3).¹² Today, with the use of dynamic CT, one more easily distinguishes cartilaginous from posterior wall collapse (see Figure 11-3). Results from studies show that dynamic CT correlates well with bronchoscopy findings,¹³ offers excellent display of anatomic details of the airway and adjacent structures,¹⁴ and allows objective interpretation and quantitative measurements of the degree of airway wall collapse before and after airway splinting interventions.^14,¹⁵ Dynamic magnetic resonance imaging (MRI) has been insufficiently studied, but small case series support its use for quantifying the degree of airway collapse¹⁶ (see Figure 11-3). Its main advantage over CT is that radiation is avoided and contrast materials used are not nephrotoxic.

Figure 11-3 Fluoroscopy reveals tracheal narrowing during expiration (bottom) as compared with inspiration (top) but cannot define which airway wall is abnormal, nor can it detect adjacent structures (A). Dynamic computed tomography shows (B) normal, physiologic dynamic airway collapse, (C) excessive dynamic airway collapse, and (D) crescent-type tracheomalacia. E, Dynamic magnetic resonance imaging reveals normal dynamic airway collapse during expiration without exposure to ionizing radiation.

We quantified this patient’s functional impairment on the basis of World Health Organization (WHO) functional class criteria.¹⁷ He had WHO class II functional impairment defined as mild limitation of physical activity without discomfort at rest, but with normal physical activity causing increased symptoms.¹⁸ The use of other dyspnea or quality of life (QOL) instruments (St. George’s Respiratory Questionnaire [SGRQ], American Thoracic Society [ATS] Dyspnea Scale, Baseline Dyspnea Index [BDI]/Transitional Dyspnea Index [TDI], Karnofsky Performance Scale [KPS], and a 6-minute walk test [6MWT]) in these patients to objectively determine response to interventions has been studied.¹⁹

Comorbidities

The patient had controlled cardiac arrhythmia and no evidence of systolic or diastolic dysfunction on 2D echocardiogram. Although moderate obstructive ventilatory impairment was noted, clinical evaluation and the 2D echocardiogram showed no evidence of pulmonary hypertension, which might prompt hemodynamic instability in case of general anesthesia.²⁰

The patient had been on prednisone 20 mg/day for 4 weeks. Traditionally, any patient who has received the equivalent of 15 mg/day of prednisone for longer than 3 weeks should be suspected of having hypothalamic-adrenal axis suppression.²¹ As a general rule, any patient who has received glucocorticoids in doses equivalent to at least 20 mg/day of prednisone for longer than 5 days is at risk for hypothalamic-pituitary-adrenal (HPA) axis suppression.²² Furthermore, this patient had been on high-dose inhaled fluticasone (440 mcg twice daily) for several years. The development of adrenal suppression from inhaled steroids is known to be related to dose, duration of therapy, and use of a potent agent (such as fluticasone).²³

Support System

The patient is married, but his wife suffers from severe COPD and is on continuous home oxygen supplementation. He is her caregiver. Investigators have found that informal caregivers (defined as untrained and unpaid persons who provide care to an ill person) have needs that go largely unmet, and that they usually receive insufficient help from services with regard to daily physical caring and emotional issues, as well as regarding information about available health and social services. Caring for a patient with dyspnea is particularly challenging and is most difficult to cope with.²⁴

Patient Preferences and Expectations

Similar to other people caring for patients with dyspnea, this patient expressed uncertainty about the future and feared there would come a time when he could no longer help his spouse, or that helping her would be done at the expense of his own health. Active participation and availability of health care professionals are needed to assist informal caregivers with coping strategies they are already using and to address future challenges. Greater involvement of health care professionals leads to sharing of information and advice, thereby enhancing the informal caregiver’s competence, especially in managing difficult symptoms such as dyspnea.²⁴ This patient was particularly motivated to improve his own symptoms so that he could maintain and improve his caregiving role for his wife. He had clearly expressed his willingness for treatment and was ready to consider all available treatment options, including noninvasive positive-pressure ventilation, airway stent insertion, and open surgical resection if necessary.

Procedural Strategies

Indications

Focal Tracheomalacia Resulting in Functional Impairment

The treatment of severe malacia often involves the use of minimally invasive or open surgical procedures.^25,²⁶ The exact degree of expiratory airway narrowing responsible for symptoms and requiring intervention remains unknown. Many investigators use 50% or greater reduction in airway caliber between inspiration and expiration to identify abnormal central airway collapse on dynamic CT or bronchoscopy.²⁷^–²⁹ This criterion, however, is applied during coughing or forced exhalation, and its use may lead to false-positive results: 78% of normal individuals exceed the current diagnostic criterion for tracheomalacia in the upper and/or lower trachea.³⁰ Furthermore, patients with other airway disorders such as bronchiolitis, COPD, or cystic fibrosis have peripheral airway obstruction, and the expiratory airway collapse seen in the central airways represents normal physiology.³¹^–³³ Indeed, during flow-limited breathing, the central airways become severely compressed, particularly during forced expiration and cough—maneuvers often used in diagnosing this entity on dynamic imaging studies. The Starling resistor model* shows that the pressure drop occurs across a very short length of airway, and that proximal airway (downstream from the choke point, mouth ward) resistance should not affect airflow. Pressure catheter measurements demonstrate this flow-limiting choke point and lack of further pressure drop in airways between the mouth and the flow-limiting segment.³⁴ Because the choke point in adult humans is often located at the level of the lobar bronchi and is even more peripheral in patients with COPD,³⁵ central airway collapsibility should not impede airflow.³²