29 Outcome Assessment in Laryngotracheal Stenosis

Laryngotracheal stenosis refers to abnormal narrowing of the central air passages from the supraglottic larynx to the carina and proximal main bronchi.1 It is caused by a heterogeneous group of diseases that have in common between them the ability to impair airflow and mucociliary clearance and in a smaller number of cases, swallowing and phonation also. The most common benign cause of this condition is intubation-related airway injury, followed by Wegener granulomatosis and idiopathic subglottic stenosis.¹

Although most cases of laryngotracheal stenosis clinically present in a similar way with exertional dyspnea and chronic stridor, the disease entities that cause these symptoms are very different. The ability to restore a prosthesis-free airway capable of meeting the ventilatory demands of the patient is therefore more determined in the long term by the natural history of the underlying disease process being treated than by the ability of an intervention to acutely improve breathing by restoring lumen dimensions. In patients with supraglottic and laryngeal stenosis, restoration of the ventilatory conduit needs also to be balanced against the risk of damaging phonatory and/or swallowing mechanisms. These factors need to be carefully considered when assessing and treating patients with this condition. Outcome assessment is essential in determining safety and success of different treatment strategies used within and between centers. This chapter begins by discussing initial patient assessment and treatment goal setting and goes on to highlight a multidimensional paradigm for assessing outcome in laryngotracheal stenosis.

Initial Patient Assessment and Treatment Goal Setting

The aims of initial assessment are to establish or confirm the diagnosis, to identify disease-specific risk factors and prognostic variables, to set realistic treatment goals in partnership with the patient, and to establish an initial management plan (Fig. 29.1).

Medical History

Assessment begins by eliciting general and disease-specific symptoms (Table 29.1). Many patients with laryngotracheal stenosis will have been initially misdiagnosed and treated for presumed “resistant” bronchopulmonary diagnoses. It is important therefore to try and obtain a clear time line of when symptoms were first noted as well as dates when initial diagnoses were made and treatments given.

Table 29.1 Initial Assessment of a Patient with Suspected Laryngotracheal Stenosis

Over half of all cases of laryngotracheal stenosis are caused by intubation-related airway injuries. Obtaining a detailed intubation history is therefore mandatory (Table 29.1). The second common cause of benign laryngotracheal stenosis is vasculitis-related airway stenosis, most commonly secondary to Wegener granulomatosis. Vasculitis symptoms need therefore to be specifically sought and if there is known or suspected vasculitis, then disease activity needs to be quantified. We use the Birmingham Vasculitis Activity Score (BVAS) for this purpose.²

Another factor which significantly impacts on treatment success is safety of swallowing, especially in supraglottic and laryngeal cases where laryngotracheal reconstruction may itself impact upon safety of swallowing, and in patients with neurological swallowing impairment where lumen restoration may lead to the development or worsening of chronic aspiration. Symptoms of chronic aspiration need therefore to be specifically sought and documented. A global assessment of patient function and ventilatory demands helps determine the most appropriate extent of reconstructive surgery.

Physical Examination

Physical examination for laryngotracheal stenosis consists of a general medical examination, an ear-nose-throat (ENT) examination, and a directed examination of the supraglottis and larynx with flexible endoscopy. Patient’s weight and height also needs to be noted. A body mass index > 40 significantly reduces the likelihood of treatment success.³

Stridor cannot reliably be elicited through auscultation during quiet breathing. It requires the patient to forcefully inspire and expire through the mouth and the clinician to auscultate over the trachea. Flexible nasoendoscopy aims to detect any obstructive supraglottic lesions, vocal fold movements, and any evidence of impaired swallowing such as hypopharyngeal pooling of secretions. If there are any concerns regarding safety of swallow, then a video fluoroscopy should be performed. A subglottic stenosis can sometimes be viewed with a flexible nasoendoscope, but this is not a reliable tool. In our practice all patients receive an examination under general anesthesia under suspension laryngoscopy and as such we do not place great reliance on outpatient tracheobronchoscopy. Outpatients tracheobronchoscopy, provided that it is done with topical laryngotracheal anesthesia and with video recording to allow detailed examination and photodocumentation of findings, is however a valid alternative method of visualizing the laryngotracheal complex.

Within intensive care settings, a patient with obstructive laryngotracheal edema or acute or pre-existing stenosis may manifest with failure to wean or decannulate or post-extubation stridor. Many cases of extubation failure or stridor are due to acute laryngotracheal edema and are successfully managed with systemic corticosteroid therapy.4 ENT assessment is often reserved for refractory or acutely life-threatening cases. The aim of this assessment is to distinguish between laryngeal swelling and obstructive granulation tissue formation (Fig. 29.2) or structural laryngotracheal deformities to determine whether minimally invasive surgery can help with critical care step-down and the degree of urgency of such treatment⁵ and whether the patient is likely to require post-discharge follow-up.

Under physiological conditions it is the performance of the cardiovascular system and not the respiratory system that limits exercise capacity. The principal objective of laryngotracheal reconstruction is therefore long-term restoration of a prosthesis-free airway whose reconstructed dimensions do not constrain the ventilatory demands of the patient while maintaining good phonation and a safe swallow. The four domains in which treatment efficacy can be assessed are anatomy, physiology, symptoms, and quality of life. Systematic documentation of occurrence and severity of disease or treatment-specific complications is also critical for assessing treatment efficacy (Table 29.2).

Treatment durability can be assessed by measuring the intertreatment interval, but this can only be meaningfully done for individual pathological disease processes. For example, idiopathic subglottic stenosis and Wegener granulomatosis are intrinsically recurrent disease processes. Deciding between what “treatment failure” is and what is treatment for recurrence of an intrinsically recurrent disease can therefore be difficult. By contrast, intubation-related airway stenosis is in most cases a nonrecurrent disease process that can be expected to be “cured” by surgery. Posttreatment recurrence in the intubation-related stenosis can therefore be considered a true treatment failure.

Assessment of Airway Anatomy

The most commonly used system for assessing stenosis anatomy is the Myer-Cotton grading system.⁶ This system is based on the degree of cross-sectional lumen encroachment. Grade I lesions encroach in between 0 and 50% of the lumen, grade II lesions obstruct between 51 and 70% of the lumen, grade III lesions obstruct between 71 and 99%, and grade IV lesions cause total lumen obliteration. This system was initially developed for assessing the subglottis in children, but has since been expanded to encompass tracheal lesions in both children and adults. More recently, Freitag et al proposed a more detailed descriptive system for assessing the nature and extent of tracheobronchial stenoses (Fig. 29.3).⁷

Table 29.2 Disease-Specific Complications in Laryngotracheal Stenosis

In 1992, McCaffrey proposed a different system which was based on the site of involvement.8 McCaffrey divided stenoses into four groups based on the length of the lesion and on whether or not the glottis was involved (Fig. 29.4). The classification was validated against actuarial time to decannulation.

In our experience the four key prognostic factors are the nature of the underlying disease process, presence of acute fibroinflammatory stenoses as opposed to mature fibrotic strictures (Fig. 29.5), site of the stenosis, and in particular whether the glottis is involved, and vertical height of the lesion (Fig. 29.6).^3,9 Details of our approach to anatomical airway assessment are provided in Table 29.3.

Some years ago we developed a system for quantitative endoscopy to determine the precise degree of luminal obstruction as an assessment method and an outcome measure.¹⁰ There had been previous and subsequent efforts by other workers to achieve the same objective and in particular, the computed tomography-based “laryngotracheal profile” by Kiesler et al provides a most eloquent approach to assess airway dimensions (Fig. 29.7).^11–13

We have, however, subsequently found detailed assessment of cross-sectional airway anatomy to be unnecessary and have reverted to using the Myer-Cotton system (Table 29.3). The reason for this is the nonlinear relationship between the degree of cross-sectional stenosis and symptoms. It has long been known that most patients are asymptomatic or minimally symptomatic for prolonged period but suddenly develop severe clinical symptoms and need to be operated on urgently.

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