F. Wheezing—Stridor

Introduction

Wheezing is manifested as high-pitched, musical, variable sounds with breathing, most prominently during expiration. The sound is generated by gas flowing through narrowed or irregular airways. In some instances it is immediately audible, but in most cases, it is heard only by auscultation of the chest. Generally, wheezing is due to asthma, although a variety of conditions may be associated with this finding.

Stridor, by contrast, is the typically shorter, crowing sound which is often evident during inspiration and expiration, but which is louder and longer during inspiration. It is heard readily without the aid of a stethoscope. Stridor is almost universally associated with mechanical or functional narrowing of the larynx or subglottic airways. Clinically, stridor is most commonly heard with either viral/bacterial infections, usually of infants and children, which result in epiglottitis or laryngitis. Sometimes, aspirated food or foreign bodies may cause acute stridor. Chronic stridor is most often the result of conditions that cause fixed narrowing of the extrathoracic airways. Laryngeal carcinoma, paralyzed vocal cords, or subglottic granulation tissue are among the more common causes of chronic inspiratory stridor. Because the causes of stridor are acutely and readily identified by clinical pattern and/or laryngeal examination, this symptom will not be discussed further in this chapter.

Various components of the history, physical examination, or laboratory assessment can aid in diagnosing asthma or the recognition of other conditions that result in wheezing. Some relatively common disorders might be mistaken for asthma (See Table 11). The table is organized by anatomical sites in order to aid with a systematic consideration of options. Table 12 includes selected elements that are useful in this process. In addition, a general principle for practitioners is to re-evaluate the diagnosis of asthma or to refer to specialists when patients do not respond satisfactorily to standard management (see above). Asthma and some of the conditions more frequently mistaken for this disorder are described briefly below.

Patients who present with episodic wheezing and dyspnea very likely suffer from asthma. However, the diagnosis should be confirmed, including steps to both document and characterize the asthma, as well as to rule out other disorders which might complicate or simulate the asthma.

Asthma

Baseline diagnostic steps in the initial evaluation include elements of history, physical examination and laboratory studies. Historical features to suggest asthma include a familial pattern, associated conjunctivitis and rhinosinusitis, seasonality, episodic appearance, worsening with coughing in late night and early morning, and/or provocation by exercise, exposure to pets, cold air, aspirin, or nonsteroidal anti-inflammatory drugs (NSAID’s). Physical examination characteristically demonstrates prolonged expiratory high pitched musical sounds heard prominently in the mid and lower lung fields. Tachypnea, tachycardia, and diaphoresis are prominent with acute illness. In severe and chronic cases, overinflation of the thorax with increased anterior-posterior diameter and limited chest wall excursion are seen. Coughing is variably prominent, typically with production of sparse but tenacious secretions. Rhinitis with boggy membranes is common. Nasal polyps may indicate “triad” asthma (asthma, sinusitis, and polyps due to aspirin sensitivity ). The key laboratory study to confirm the diagnosis of asthma is spirometry, which typically demonstrates reduced forced expiratory volume in one second (FEV1) that is reversible with inhalation of ß-adrenergic aerosols. Between episodes, however, pulmonary function tests (PFT’s) may be normal. In patients suspected of having asthma but whose initial spirometric studies are normal, bronchial challenge tests with histamine or methacholine will reveal bronchial hyperresponsiveness; in its absence, alternative diagnoses are likely. Seasonal, allergically-mediated asthma may be accompanied by peripheral blood eosinophilia and elevated levels of immunoglobulin E (IgE). Other investigations to identify disorders that may complicate asthma include CT scans of the paranasal sinuses and assessment for gastroesophageal reflux by barium contrast studies or 24-hour pH monitoring. Among children and young adults with asthmatic symptoms and abnormal spirometry with partially reversible obstructive deficits, consideration should be given to the co-existence of mild forms of cystic fibrosis. Chest x-rays need not be done with typical asthma that is readily responsive to therapy. But among patients with complicated or poorly responsive wheezing syndromes, radiographic studies may help suggest alternative diagnoses as delineated in Table 12. Specific features of the more common disorders that are potentially confused with asthma are described below.

Vocal Cord Dysfunction Syndrome (VCDS)

Several articles have described patients with episodic dyspnea, wheezing, and airflow obstruction originating in the larynx. Vocal cord dysfunction syndrome (VCDS) merits particular emphasis due to its recent recognition and the general lack of familiarity on the part of clinicians. Also of importance is the potential for immense iatrogenic morbidity if misdiagnosed as refractory asthma.

Typically, VCDS is associated with inspiratory wheezing due to paradoxical closure of the cords. Features which help to distinguish it are: failure to respond to standard therapy, inspiratory stridor (the anomaly of inspiratory wheezes may be overlooked due to the patient’s dramatic distress), the patient’s indication that the obstruction is most pronounced in the neck, coarseness of voice around the attacks, the absence of hypoxemia despite severe respiratory distress, and the failure of patients to report nocturnal awakening or early morning symptoms.

VCDS is thought to be a conversion reaction, not deliberate malingering. Two groups have been noted to be at greater risk: women, ages 20 to 50 years, many of whom work in helping or para-medical roles, and young adolescents who are high-achieving athletes or students and whose attacks come at times of stress.

Diagnosis of VCDS is based upon the clinical presentation, evidence of upper airway obstruction and laryngoscopic demonstration of anomalous vocal cord motion. Treatment entails speech therapy, psychological intervention, and weaning from asthma medication (provided that there is documentation of the absence of bronchial hyperresponsiveness). Most critically, patients should be withdrawn from the high doses of corticosteroids that they are typically receiving for “refractory asthma”.

Other Disorders Commonly Mistaken for Asthma

In addition to VCDS, the following are notable for the frequency with which they are mistaken for asthma.

Central Airway Masses: Granulation or scar tissue may form within the subglottic area or trachea following tracheostomy or prolonged intubation. This may produce substantial impairment of airflow, wheezing and dyspnea. Similarly, thyroid masses may compress this region of the trachea. If the obstructing lesion lies outside the thorax, inspiratory stridor may be the most prominent manifestation. Lower lesions may cause both inspiratory and expiratory wheezing.

Bronchial Masses: Various obsructive lesions, benign or malignant, may narrow the lumina of major bronchi, causing dyspnea, wheezing and cough. Aspirated foreign bodies and bronchial adenomas are especially prone to confusion with asthma due to their occurrence in younger persons and the absence of systemic findings to suggest the diagnosis.

Small Airway Lesions: Bronchiolitis obliterans (BO), a disorder characterized by obstructive proliferation within the very small peripheral airways, also confounds the diagnosis of asthma. Associated with a variety of predisposing diseases or idiopathic, BO typically presents with cough and shortness of breath. Wheezes may or may not be present. In contrast to BO with organizing pneumonias (BOOP), the chest x-ray is usually within normal limits or mainly shows overinflation. High resolution CT may reveal patchy or mosaic variation of lung tissue density thought to reflect heterogeneous zones of air-trapping caused by BO. Spirometry reveals reduced expiratory airflow with minimal or no improvement with bronchodilators. Many patients, however, respond to systemic corticosteroids, sometimes leading to a diagnosis of variant asthma. Diagnosis is made by lung biopsy.

Cardiogenic Disorders: Cardiogenic pulmonary edema has considerable clinical overlap with asthma. Episodic dyspnea, nocturnal worsening, aggravation with exercise, and, on occasion, wheezing that responds to bronchodilators, are all potential components of cardiogenic pulmonary edema. Therefore, careful review of risk factors plus physical examination and laboratory studies to identify cardiac dysfunction are essential.

When to Refer

Most individuals who complain of episodic dyspnea, chest tightness and anxiety that is associated with expiratory wheezes have asthma. Spirometry should be done to confirm the diagnosis and to quantify the degree of airway obstruction. These patients should be managed in accordance with recently published guidelines and their treatment stratified by disease severity. However, among individuals with uncharacteristic symptoms, physical findings or laboratory studies, alternative diagnoses should be considered. Failure to respond to conventional treatment, including the requirement for chronic oral steroids, should be regarded as an important indication for referral.

Medicolegal Concerns

Perhaps the most compelling considerations are the morbidity that derives from extended, inappropriate use of corticosteroids for conditions other than asthma or from delayed/missed diagnosis of central airway narrowing from tumors or foreign bodies. Also, failing to provide to the patient and/or family a plan of care for escalating or refractory symptoms is deemed substandard practice.

Summary

It is still true that “not all that wheezes is asthma”. However, most is! Historical, radiological, and physical findings as well as pulmonary function testing generally allow clinicians to distinguish asthma from other conditions. But, among selected patients, alternative diagnoses may prove diagnostically elusive. By considering Tables 6-1 and 6-2 and the narrative sections above, practicing physicians should be assisted in recognizing asthma and the diverse conditions which can mimic this disorder.

References

Cormier YF, Camus P, Desmeules MJ. Nonorganic acute upper airway obstruction: description and diagnostic approach. Amer Rev Respir Dis 1980;121:147-150.

Pitchenik AE. Functional laryngeal obstruction relieved by panting. Chest 1991;100:1465-1467.

Christopher KL, Wood RP, Eckert RC, Blager FB, Raney RA, Souhrada JF. Vocal-cord dysfunction presenting as asthma. New Engl J Med 1983;308:1566-1570. The above 3 references give descriptions of patients in whom upper airway abnormalities causing wheezing were mistakenly misdiagnosed and mistreated as asthma.

Kryger M, Bode F, Antic R, Anthonisen N. Diagnosis of obstruction of the upper and central airways. Am J Med 1976;61:85-93. An excellent review of the diverse physiological findings associated with obstructing lesions/processes in the large airways, trachea and extrathoracic airways.

National Institutes of Health. National Heart, Lung, and Blood Institute: Expert panel report 2: guidelines for the diagnosis and management of asthma. NIH Publ No. 97-4051, 1997. Guidelines that clarify asthmatic severity and offer stratified or “stepwise” recommendations for treatment.

Wright JL, Cagle P, Churg A, Colby TV, Myers J: Diseases of the small airways. Am Rev Respir Dis 1992;146:240-262. A comprehensive review of a variety of conditions associated with inflammation and compromise of the small airways including bronchiolitis obliterans and BOOP.

E. Hemoptysis < back | next > G. Positive Tuberculin Skin Test
9 of 23 HTML pages