see also:

• the chest X-ray (CXR)

• the diaphragm normally flattens during inspiration
• the diaphragm is the primary muscle for inspiration since it accounts for 80% of the power required for respiration.
• an elevated hemidiaphragm is usually an incidental finding on an inspired CXR and generally not symptomatic due to the compensation and recruitment of other inspiratory muscles and the other hemidiaphragm
• HOWEVER, it may cause issues, particularly if increased abdominal pressure restricts the other hemidiaphragm:
  • reduced vital capacity causing SOB, and on lung function tests, a restrictive pattern
    • elevated hemidiaphragm will show a reduced forced vital capacity (FVC) of 30% of the standard predicted value.
    • with bilateral diaphragm paralysis, the FVC may decrease by 75% of the expected value
  • reduced IVC blood flow causing reduced cardiac output similar to that which occurs in cardiac tamponade
    • normally, the intrathoracic pressure and contraction of the diaphragm overcome the force of gravity and propel blood into the right atrium from the inferior vena cava (IVC)
• less commonly, it may be bilateral

• the diaphragm has three points of origin, creating a C shape that culminates in a stable, dense fibrous center tendon:
  • sternal group of muscle fibers is attached to the posterior aspect of the xiphoid process
  • costal group of muscle fibers originates from the inner surface of seven to twelfth ribs
  • lumbar group of muscular fibers arises from the medial and lateral arcuate ligaments and anterior longitudinal ligament, and lumbar vertebral bodies of L2-L3
• there are three openings in the diaphragm, allowing structures to pass between the thoracic and abdominal cavity:
  • the oesophageal hiatus through which the esophagus and vagus nerve pass
  • the aortic hiatus through which the aorta, azygos vein and thoracic duct pass
  • the caval hiatus through which the inferior vena cava passes
• each side has it's own blood supply from the inferior and superior phrenic arteries arising directly from the aorta, subcostal and intercostal arteries.
• each hemidiaphragm is innervated by the ipsilateral phrenic nerve that arises from the cervical nerve roots of C3-C5
  • each phrenic nerve emerges through the anterior scalene muscle on either side of the neck and courses posteriorly to the subclavian vein
  • in the thoracic cavity, the right and left phrenic nerves follow different paths:
    • the right phrenic nerve descends anteriorly over the right atrium of the heart and exits through the inferior vena cava opening to innervate the inferior surface of the hemidiaphragm
    • the left phrenic nerve crosses the aortic arch and pericardium overlying the left ventricle until it pierces through the diaphragm to innervate the inferior surface of the left hemidiaphragm
• sensory innervation of the diaphragm is from the intercostal nerves 6-11

• phrenic nerve palsy
  • UMN
    • MCA stroke
    • multiple sclerosis (MS)
    • upper cervical spine injury or conditions
  • LMN
    • cervical spinal cord trauma or disease
      • poliomyelitis
    • trauma, damage to or pressure on a phrenic nerve
      • neck surgery
      • brachial plexus palsy
      • cervical spine injury
      • cervical spondylosis
      • bronchial artery embolization
      • interscalene blocks for procedures in shoulder injuries such as rotator cuff repair, humeral fracture, shoulder replacement surgery
      • common complication of cardiac surgery (usually left side)
      • intrathoracic tumours or lymphadenopathy pressing on the phrenic nerve
• neuromuscular disorders (often cause bilateral palsies)
  • amyotrophic lateral sclerosis (ALS)
  • myasthenia gravis
  • muscular dystrophy
  • 25% of patients with Guillain-Barre disease will develop diaphragmatic weakness requiring mechanical ventilation
• intrathoracic pathology
  • pneumothorax
  • atelectasis
  • partial or complete pneumonectomy
  • congenital defects: pulmonary hypoplasia or diaphragmatic eventration
  • chronic coughing in asthmatics rarely may cause a spontaneous diaphragmatic hernia

• congenital diaphragmatic eventration (partial or incomplete muscularization of the diaphragm)
  • these are usually R sided in the anteromedial portion
  • there is only a thin membrane instead of muscle
• direct injury to the diaphragm from penetrating trauma such as a stab wound

• hepatomegaly or liver tumours
• subphrenic abscess
• pneumoperitoneum (free air under diaphragm)
  • perforated viscus
  • post-laparoscopy
• Chilaiditi sign - air below the right diaphragm due to colon wrapping above the liver
  • this may rarely cause Chilaiditi syndrome if that bowel becomes obstructed

• distention of the stomach
• abdominal tumors
• distended abdomen
• subphrenic abscess
• splenomegaly
• colon malrotation
• pneumoperitoneum (free air under diaphragm)
  • perforated viscus
  • post-laparoscopy

• pleural effusion
• diaphragmatic hernia
• traumatic diaphragmatic rupture
• diaphragmatic or pleural tumour eg. mesothelioma

• ultrasound
  • during inspiration, when the diaphragm contracts, it is about 20% thicker than at the end of quiet respiration
  • diaphragmatic weakness is suggested if the thickness does not increase by 20% or if the diaphragm thickness is <15mm
  • paradoxical movement of the diaphragm during inspiration indicates paralysis of the diaphragm
  • these may be repeated every 6 months to assess progress and failure to resolve function in a symptomatic patient may be indication for plication surgery
• fluoroscopy if not ultrasound available
  • the weakened hemidiaphragm will move paradoxically during inspiration
• consider CT chest
  • especially if trauma or suspect malignancy

• laparoscopic diaphragmatic plication
  • weakened hemidiaphragm is sewn to the central tendon and peripheral muscles and improves ventilation
• phrenic nerve pacing
  • through diaphragm motor unit mapping and electrode placement has successfully assisted in the recovery of patients with spinal cord injury (SCI