December 06, 2015

Q&A: Evaluation of Acute Breathlessness and Wheeze

Wheezing is a common manifestation of respiratory illness in adults. While wheezing typically brings to mind airway obstruction from bronchoconstriction or excessive mucus production and/or poor clearance due to asthma or chronic obstructive pulmonary disease (COPD), wheezing is also caused by a spectrum of other processes that cause airflow limitation. These processes may be present on their own or may coexist with asthma or COPD, contributing to difficult to control symptoms. When evaluating wheezing, it may be helpful to recall the adage, "All that wheezes is not asthma [or COPD]; all that wheezes is obstruction."

This article is for Medical Students & Professionals
This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Wheeze article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
Evaluation of acute wheeze and respiratory distress
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Evaluation of acute wheeze and respiratory distress

Our first step in evaluating a patient with wheezing is to determine the severity of respiratory compromise and the rapidity of worsening of any associated shortness of breath. For patients with rapid onset of respiratory distress associated with wheezing or stridor, the key initial steps are to ensure adequate oxygenation and ventilation based on pulse oximetry and arterial blood gas measurement. Supplemental oxygen is administered, and a rapid assessment made to determine the most likely cause. If asthma and chronic obstructive pulmonary disease (COPD) are likely, nebulized bronchodilator treatment is immediately given. If there is evidence of anaphylaxis, subcutaneous epinephrine should be given.

For patients with impending respiratory failure and suspicion of central airway obstruction (eg, due to stridor, tachypnea, lack of response to inhaled bronchodilator), endotracheal intubation by an experienced clinician may be necessary prior to a diagnostic evaluation if the initial measures have failed to improve the situation. If endotracheal intubation cannot be performed immediately, inhalation of a helium-oxygen mixture with a helium concentration of at least 40 percent may allow temporary stabilization of respiratory status.

For severe tracheal obstruction, use of an open ventilating rigid bronchoscope may be necessary. At the time of intubation, the larynx and vocal folds are examined for evidence of mass or paralysis. After intubation, the intrathoracic airway can be examined by flexible bronchoscopy through the endotracheal tube. Resolution of wheeze with intubation suggests that the area of obstruction is in the upper airway and may be extrathoracic.

For patients not needing emergent intubation, a high resolution chest computed tomography (CT) with three-dimensional airway reconstruction can help identify and characterize any central airway obstruction. Direct visualization of the airway is often needed to diagnose the specific cause.

Paroxysmal vocal cord dysfunction can sometimes present with acute respiratory distress and stridor, but does not require intubation.

MCQ exam: clinical scenario

A 23 year old female banker presents to the Emergency Department with shortness of breath. She is wheezing, can barely speak and prefers to sit leaning forwards. She is a known asthmatic who has been using her prescribed steroid inhaler regularly. Few days earlier, she had visited her general practitioner for a cough, for which she was prescribed Erythromycin tablets, but the cough had persisted and deteriorated into her present clinical state.

Which of the following causes of respiratory failure is recognized to have the highest mortality rate?

a). Chronic obstructive pulmonary disease (COPD)
b). Asthma
c). Acute respiratory distress syndrome (ARDS)
d). Obesity
e). Neuromuscular disease

MCQ questions & answers on

MCQ exam: answer

The correct answer is C.

MCQ exam: explanation

The mortality associated with respiratory failure varies according to the etiology. For ARDS, mortality is approximately 40%-45%; this figure has not changed significantly over the years. Younger patients (<60 years) have better survival rates than older patients. Approximately two thirds of patients who survive an episode of ARDS manifest some impairment of pulmonary function 1 or more years after recovery.

Significant mortality also occurs in patients admitted with hypercapnic respiratory failure. This is because these patients have a chronic respiratory disorder and other comorbidities such as cardiopulmonary, renal, hepatic, or neurologic disease. These patients also may have poor nutritional status.

For patients with COPD and acute respiratory failure, the overall mortality has declined from approximately 26% to 10%. Acute exacerbation of COPD carries a mortality of approximately 30%. The mortality rates for other causative disease processes have not been well described.

A study by Noveanu et al suggests a strong association between the preadmission use of beta-blockers and in-hospital and 1-year mortality among patients with acute respiratory failure. Although cessation exacerbates the mortality, predischarge initiation of beta-blockers is also associated with an improved 1-year mortality.

1). Noveanu M, Breidthardt T, Reichlin T, Gayat E, Potocki M, Pargger H, et al. Effect of oral beta-blocker on short and long-term mortality in patients with acute respiratory failure: results from the BASEL-II-ICU study. Critical Care (London, England), 03 Nov 2010, 14(6):R198
DOI: 10.1186/cc9317 PMID: 21047406 PMCID: PMC3219994.
2). UpToDate: Evaluation of wheezing illnesses other than asthma in adults. Available online:

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