What is the role of pulmonary function testing in the workup of diaphragmatic paralysis?

Updated: Oct 10, 2018
  • Author: Justina Gamache, MD; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Measuring the vital capacity in the upright and supine positions is the most important part of the pulmonary function test.

Diaphragmatic paralysis reduces the measured compliance of the lungs and a restrictive pattern can develop.

Normally, vital capacity in recumbency decreases by 10%. In contrast, patients with bilateral diaphragmatic paralysis show a 50% decrease in vital capacity when they are supine. This decrease is from cephalad displacement of abdominal contents.

Pulmonary function test results, however, are not always consistent and do not always correlate with the severity of dyspnea from diaphragmatic paralysis. [9]

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