A 64-year-old woman comes to the office due to worsening dyspnea on exertion and a "whistling noise" while breathing heavily during exercise. These symptoms have worsened over the past 3 months. The patient has had no cough, fever, hoarseness, or weight change. She has hypertension and hyperlipidemia and had a coronary artery bypass graft 4 years ago. Physical examination reveals no cardiopulmonary abnormality. A flow-volume loop demonstrates the following:

What is the most likely etiology of this patient's symptoms?

Question

A 64-year-old woman comes to the office due to worsening dyspnea on exertion and a "whistling noise" while breathing heavily during exercise. These symptoms have worsened over the past 3 months. The patient has had no cough, fever, hoarseness, or weight change. She has hypertension and hyperlipidemia and had a coronary artery bypass graft 4 years ago. Physical examination reveals no cardiopulmonary abnormality. A flow-volume loop demonstrates the following:

What is the most likely etiology of this patient's symptoms?

Quizplus · Accepted Answer

11ec193a_98ed_03cb_853d_37d28fd73596_MD0002_00 A flow-volume loop trends airflow rate through the large airways (y-axis) with change in lung volume (x-axis) during a respiratory cycle. The loop begins when the patient is at full inhalation or total lung capacity (point "a" in the graph) and starts to exhale at full force (upper half of graph). Complete exhalation (patient at residual volume) is followed by a quick inhalation and the patient returns to total lung capacity (point "a"). Blunting of the flow-volume curve occurs when airflow is limited by upper airway (mouth to lower trachea) obstruction. Obstruction can be dynamic (either inspiratory or expiratory) or fixed (both inspiratory and expiratory). Fixed upper airway obstruction, as seen in this patient, causes blunting of both limbs of the loop due to reduction of airway diameter. This pattern may be seen with obstructive substernal goiters; these extend through the thoracic inlet into the thoracic cavity and therefore may not be visible on physical examination. As goiters may occur in patients in a euthyroid state, symptoms of a substernal goiter may present as exertional dyspnea, wheezing, cough, or a choking sensation. Tracheal stenosis can also cause a fixed obstruction. Fixed upper airway obstruction (Choices A and B) Asthma and emphysema cause a greater reduction in initial airflow (forced expiratory volume in 1 second) followed by a sharp decline in the airflow rate. This results in the classic "scooped out" appearance of the expiratory loop due to obstruction of the lower airways with loss of elastic recoil (in emphysema) or constriction (in asthma). "scooped out" appearance (Choices D and E) Dynamic or variable obstruction is seen when airflow is limited in either inspiration or expiration. Intrathoracic lesions (eg, tracheomalacia) limit airflow during exhalation due to compression of the airway from increased intrathoracic pressure. Extrathoracic lesions such as those causing vocal cord paralysis tend to get "tugged in" on inspiration, resulting in a blunted inspiratory limb. Educational objective: Fixed upper airway obstruction limits airflow in both inhalation and exhalation. Extrathoracic dynamic obstruction causes blunting of the flow-volume loop during inhalation (airway "tugged in"). Intrathoracic dynamic obstruction limits airflow during exhalation (compression from increased intrathoracic pressure). __________ References: Flow volume loop as a diagnostic marker. (http://www.ncbi.nlm.nih.gov/pubmed/23741103)

A 64-Year-Old Woman Comes to the Office Due to Worsening