Diaphragmatic paralysis other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

Other diagnostic studies for diphragmatic paralysis include pulmonary function test which demonstrates mild decrease in vital capacity in unilateral diaphragmatic paralysis and and [diagnostic study 2], which demonstrates [finding 1], [finding 2], and [finding 3].

Other Diagnostic Studies

Pulmonary function test:

• 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:
    • 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 )
    • Total lung capacity may be reduced
    • Residual volume (RV) may be elevated

Maximal inspiratory pressure (MIP) :

Maximal inspiratory and expiratory pressures (MIP, MEP) are measured to confirm respiratory muscle weakness. The maximal inspiratory pressure (MIP) reflects the strength of the diaphragm. Patients with diaphragmatic dysfunction or paralysis have decreased MIPs. This is especially true in those with systemic or generalized neuromuscular disease. The MIP in patients with bilateral diaphragm paralysis is lower (less negative) than -60 cm H2O. Rarely, the MIP is normal in patients with isolated diaphragmatic paralysis because of preserved strength of the accessory muscles. The MEP is usually normal, but may be mildly reduced, as it is measured at full inspiration and patients with diaphragmatic paralysis are unable to achieve full inspiration. The ratio of MEP over MIP (MEP/MIP) >2 has been useful as a screening test for diaphragmatic dysfunction

• MIP shows the strength of the diaphragm.
• MIP can be decreased:
  • Less than 60% of the predicted value in unilateral diaphragmatic paralysis
  • 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.

Electromyography

• 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 eyiology.
• Absence of an EMG signal is seen in complete transection of the phrenic nerves

Polysomnography 

• 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.