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· Composed of a central tendinous portion and a peripheral muscular portion
· Muscular portion consists of sternal, costal, and lumbar components
· Three major openings: aortic (aorta, azygos vein, thoracic duct), esophageal (esophagus, vagus nerves), caval (IVC)
· Right and left phrenic arteries arise from the abdominal aorta
· Additional arterial supply from pericardiophrenic and musculophrenic arteries
· Venous drainage is via right and left phrenic veins to the IVC; some drainage to the left renal vein as well
· Right and left phrenic nerves supply both sensory and motor innervation
A. Bochdalek's Hernia
· Occurs posterolateral in the area of the 10th and 11th ribs
· 90% occur on the left
· 2:1 male to female incidence
· Usually isolated and not associated with other congenital defects
· Typically manifests as acute respiratory distress
· CXR demonstrates intestine in the thorax and shift of mediastinal contents to the right
· Initial treatment includes NG decompression, positive-pressure ventilatory support, and surgical correction
· Approach left-sided defect through the abdomen in order to explore for malrotation and obstruction
· Right-sided defects are repaired through a thoracotomy
· Postoperative mortality can be as high as 50%, mostly attributed to increased pulmonary vascular resistance
· ECMO is useful to reduce pulmonary vascular resistance and help resolve persistant fetal circulation
B. Morgagni's Hernia
· Defect occurs in a subcostosternal location
· Uncommon (less than 3% of diaphragmatic hernias) and usually asymptomatic
· Well defined hernia sac becomes symptomatic typically after age 40, when obesity, pregnancy, or trauma increases intraabdominal pressure
· The transverse colon is the most common organ to herniate, and can present as an acute colonic obstruction
· Repair is usually performed through a upper midline incision
C. Esophageal Hiatal Hernia
· Congenital defects causing these hernias are uncommon in adults, but some neonates and infants may have reflux associated with an esophageal hiatal hernia
· Typical symptoms are vomiting, respiratory complications, anemia, and failure to thrive
· Diagnosis rests on esophagography, fluoroscopy, and pH monitoring
· Treatment is primarily medical; surgery is indicated for medical failure
A. Primary
· Rare tumors; cysts are more common than inflammatory masses, which are more common than neoplasms
· Equal male:female incidence; left-sided tumors are slightly more common than right-sided tumors
· Symptoms include pain, cough, dyspnea, and GI symptoms
· CXR and CT scan will localize the tumor
· The majority of neoplasms are benign (60%), which are usually cysts
· Up to 40% are malignant, usually sarcomas
· Treatment includes excision and closure of the diaphragmatic defect
B. Metastatic
· Most neoplastic involvement of the diaphragm occurs from contiguous extension of nearby tumors
· The most common lesions arise from lung, esophagus, stomach, liver, and the retroperitoneum
· Treatment is based on the primary tumor
· Penetrating perforation should be suspected with any thoracic injury below the level of the nipples (5th ICS)
· Most blunt hernias are caused by automobile accidents, and about 90% occur in the left hemidiaphragm
· Blunt trauma defects are large, usually about 10-15 cm, and typically located in the posterior left hemidiaphragm
· Stomach is the most commonly herniated organ, followed by spleen, colon, small bowel, and liver
· Respiratory insufficiency is common early, while intestinal obstruction predominates later
· CXR and CT scan will diagnose most; barium contrast is contraindicated, as it can produce a total obstruction in this setting
· Missed injury and delayed diagnosis commonly leads to bowel incarceration and obstruction
· Mortality is relatively high (15-40%) due to high incidence of associated injuries
· Repair should be undertaken promptly with full exploration for other injuries
· Left-sided perforation should be repaired through the abdomen to allow correction of associated injuries
· Right-sided perforations may require thoracotomy
A. Indications
· Sarnoff (1940's) and Glenn (1950's) were the primary developers of diaphragmatic pacers
· Pacing is indicated in patients who have chronic ventilatory insufficiency with normal nerves, lungs and diaphragm
· This includes some quadriplegic patients and central alveolar hypoventilation
· Contraindications to pacing are lower motor neuron dysfunction, muscular dystrophy, and extensive lung disease
B. Mechanism
· There are four components to a diaphragmatic pacer:
1) Transmitter: sets respiratory rate and length of inspiration
2) Antennae: transfers signal across intact skin to the receiver
3) Receiver: obtains signal and energy from external portion by inductive coupling
4) Electrode: stimulates the phrenic nerve
· The electrode portion is usually implanted on the phrenic nerve through the 2nd ICS anteriorly
· The receiver is placed in a subcutaneous pocket
C. Central Alveolar Hypoventilation
· Features of CAH include: hypoxemia and hypercapnia increasing with sleep, hypoventilation or apnea during sleep, and clinical findings of cyanosis, polycythemia, and cor pulmonale
· These patients have near-normal ventilatory capacity tests, but have a reduced response to induced hypoxemia and hypercapnia
· Absence of upper airway obstruction or persistence after relief must also be demonstrated
· These patients should begin pacing within 3 weeks of operation
D. Quadriplegia
· Patients with high cervical lesions (C1 or C2) are suitable candidates; injury to C3-C5 may injure the motor component of the phrenic nerves, preventing adequate pacing
· Delay surgery for several months to allow for potential recovery after spinal cord injury
· Pacing should be gradually introduced to avoid diaphragmatic fatigue and permanent damage
· Patients should be selected who are good candidates for long-term rehabilitation