Diaphragmatic paralysis other diagnostic studies

Other diagnostic studies for diphragmatic paralysis include pulmonary function test which demonstrates decrease in vital capacity in diaphragmatic paralysis. Maximal inspiratory pressure (MIP) can be decreaed. Electromyography and polysomnography are other diagnostic studies.

• Spirometry in the supine and sitting positions may be helpful in the diagnosis of diaphragmatic paralysis. Findings suggestive of diaphragmatic paralysis include:
  • Unilateral diaphragmatic paralysis:^[1]
    • Mild decrease in vital capacity (VC): 75% of the predicted value and further decrease (10% to 20% in the supine position)
    • Functional residual capacity (FRC) and total lung capacity (TLC) are usually unchanged.
  • Bilateral diaphragmatic paralysis:
    • Decrease in vital capacity (VC): 50 % of the predicted value and further decrease (30% to 50% in the supine position )^[2]
    • Total lung capacity may be reduced
    • Residual volume (RV) may be elevated^[3]

• MIP shows the strength of the diaphragm.
• MIP can be decreased:
  • Less than 60% of the predicted value in unilateral diaphragmatic paralysis^[2]
  • Less than 30% of the predicted value in bilateral diaphragmatic paralysis

• Maximal expiratory pressure (MEP) is normal.
• MEP/MIP >2 is supportive of the diagnosis of diaphragmatic paralysis.

• It is not usullay done because it is very invasive.

• Electromyography (EMG) is not very useful in unilateral diaphragmatic paralysis.
• Electromyography (EMG) in bilateral diaphragmatic paralysis may reveal neuropathic or myopathic pathern besed on the etiology. ^[4]
• Absence of an EMG signal is seen in complete transection of the phrenic nerves

• Dyspnea and disturbed sleep are usully seen in bilateral diaphragmatic paralysis. It is better that overnight polysomnography is done to rule out sleep related disorders that cause breathing dysfunction. ^[5]

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