Bilateral Diaphragmatic Paralysis


  • Pulmonary HTN due to neuromuscular disease (due to bilateral diaphragmatic paresis or paralysis)
  • Hypoventilation leads to hypoxia/acidosis (with resultant pulmonary vasoconstriction)


  • Polydermatomyositis (see [[Polydermatomyositis]])
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  • PFT (restriction):
    • Decreased VC (due to muscle weakness, decreased lung, chest wall compliance): supine VC << upright VC (normals show approximate 20% decrease with change in position, but Bilateral Diaphragmatic Paralysis patients show >25-50% decrease)
    • Decreased TLC
    • Increased RV (due to inability to overcome recoil of chest wall outward at volumes below FRC)
    • Decreased MVV
    • Decreased MIP/ MEP
    • Decreased compliance (due to chronically low lung volumes: microatelectasis/ reduced surface tension/ altered interstitial elastic fibers)
    • Transdiaphragmatic pressure (with esophageal and gastric balloons): reveals decreased pressure gradient
  • CXR: low lung volumes/ possibly aspiration pneumonia
  • Diaphragmatic EMG/ NCV: may reveal myopathic changes, neuropathic changes, anterior horn cell disease


(usually symptomatic)

  • Exertional dyspnea
  • Orthopnea (due to pressure of viscera on diaphragm)
  • Dullness/ decreased BS at bases
  • Tachypnea (in severe disease)
  • Scalene/Sternocleidomastoid contractions
  • Paradoxic inward movement of abdomen with inspiration (classic)
  • Respiratory failure
  • Aspiration pneumonia
  • Sleep-disordered breathing
  • Acute/Chronic Hypoventilation (see Acute Hypoventilation, [[Acute Hypoventilation]] and Chronic Hypoventilation, [[Chronic Hypoventilation]])
  • Pulmonary Hypertension/Cor Pulmonale (see Pulmonary Hypertension, [[Pulmonary Hypertension]])


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