About 90% of Dr. Mirza’s patients are female. When she sees PVFM in men, they also tend to have asthma, she noted.
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May 2009
Careful Diagnosis Needed
PVFM is often mistaken for asthma on initial diagnosis, noted Dr. Aviv. The condition may also be confused for lung disease or merely being out of shape, he added.
About 30% of patients with asthma also have some element of paradoxical dysfunction, said Dr. Mirza. However, if patients with asthma are not responding to inhalers as well as they should, she usually suspects PVFM as the primary cause of symptoms.
Physicians and therapists have to be careful when working with this population to make a differential diagnosis, said Dr. Mathers-Schmidt.
Taking a Medical History
Because patients often don’t have any significant PFVM symptoms when they come into the office, Dr. Mirza relies on medical history and clinical suspicion for a diagnosis.
Generally, patients with PVFM often complain of experiencing cough or shortness of breath during exercise, noted Dr. Aviv. PVFM symptoms also tend to occur after an upper respiratory infection. We think a cold or flu has caused vagus nerve injury, leading to shortness of breath, he said.
In addition to taking a medical history, practitioners often observe patients while engaged in the level of activity that tends to induce PVFM, said Dr. Mathers-Schmidt. Many people I’ve worked with experience PFVM as they shift to a higher level of activity, she said. A soccer player could be playing just fine, but once she increases her activity for a fast sprint, she’ll experience PFVM.
Examination and Pulmonary Function Tests
Examination of the vocal folds is another important part of diagnosis. Dr. Mirza often uses flexible laryngoscopy to visualize the vocal folds of patients with suspected exercise-induced PVFM after they have engaged in the physical activity that typically triggers their symptoms.
Dr. Klaben sometimes uses videostroboscopy to examine both vocal folds to see if they are moving correctly and to ensure that no obstruction is present.
Patients with suspected PVFM may also undergo pulmonary function testing. If the condition is present, a truncated flow loop diagram will be produced during inspiration, said Dr. Klaben. The ratio of forced expiratory and inspiratory flow at 50% vital capacity is normally less than 1, but with PVFM, the inspiratory obstruction result in a ratio greater than 1, she explained.