Whistling in the Dark

Posted by Sara Fazio • May 4th, 2012

In a new Clinical Problem-Solving article, shortness of breath, fever, and cough productive of yellow sputum developed in a 38-year-old woman soon after the birth of her third child. Although her symptoms initially resolved with antibiotics, an intermittent nonproductive cough, wheezing, and shortness of breath soon followed.

It is important to consider a broad differential diagnosis for wheezing, especially when findings are atypical for asthma or when symptoms fail to subside as expected in response to conventional therapy. This case highlights the importance of measuring lung function both when attempting to confirm (or rule out) a diagnosis of asthma if it is suspected and when adjusting medications in patients with established asthma.

Clinical Pearls

• What is the differential diagnosis of a patient who presents with a cough and wheezing?

Recurrent episodes of shortness of breath, cough, and wheezing suggest a diagnosis of asthma. Nocturnal worsening of symptoms is consistent with this diagnosis. Atypical features, opening the possibility of alternative diagnoses, would be a late age at onset and the absence of identifiable triggers for the symptoms. Other potential causes include recurrent respiratory tract infections, gastroesophageal reflux with microaspiration of gastric contents, and congestive heart failure, including that resulting from valvular heart disease or diastolic dysfunction, which may cause “cardiac asthma.”

• How does aspirin-associated respiratory disease present?

Aspirin-exacerbated respiratory disease often presents in adulthood with a characteristic sequence of recurrent sinusitis, followed by the development of asthma and then the recognition of exacerbations of asthma precipitated by ingestion of aspirin or any other cyclooxygenase-1 inhibitor.

Morning Report Questions

Q: How does one make the diagnosis of tracheomalacia?

A: The diagnosis of tracheomalacia may be made with the use of fiberoptic bronchoscopy, but the speed of image collection on modern multidetector CT equipment makes chest CT a useful alternative means of diagnosis. Images should be obtained during inspiration and expiration and then compared. For images collected during expiration, the goal is to maximize the abnormal movement of the posterior tracheal wall (or any other malacic portion of the wall). The best time to obtain the image is near but not at the end of exhalation, when the pleural pressure is still positive. Precise criteria for radiographic diagnosis of tracheomalacia have not yet been defined, but many radiologists use a luminal narrowing of 50% on exhalation as a benchmark.

Q: What is the most common cause of tracheomalacia?

A: In adults, the most common cause of tracheomalacia is prolonged mechanical ventilation; high pressures in the endotracheal tube cuff may cause localized ischemic injury to the tracheal wall (the cartilage and the membranous sheath). Other causes of segmental tracheomalacia include prolonged external pressure on the tracheal wall, such as may be caused by a large substernal goiter or a congenital vascular sling (e.g., a right-sided aortic arch with an aberrant subclavian artery). More diffuse tracheomalacia is encountered in patients with the rare conditions of tracheobronchomegaly (Mounier-Kuhn syndrome) and relapsing polychondritis.

One Response to “Whistling in the Dark”

  1. Brian Sabb says:

    Hi,

    Thanks for another educational post, keep up the great work.

    While it is true that many radiologists use the 50% criteria as stated above, recent research makes this number difficult to apply.

    An article by Dr. Boiselle in Radiology 2009 noted that in 51 healthy volunteers: “The mean percentage of expiratory reduction in tracheal lumen cross-sectional area was 54.34% +/- 18.6 (standard deviation) in the upper trachea and 56.14% +/- 19.3 in the lower trachea.”

    78% of their healthy population exceeded the 50% cut off that is used to diagnose tracheomalacia.

    Thanks for another interesting post.

    Sincerely,

    Dr. Brian Sabb
    http://www.linkedin.com/in/briansabb

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