Lungs Have a Dual Arterial Blood Supply (Insights Imaging, 2020) [MEDLINE]

Pulmonary Arteries

• Function
  • Pulmonary Arteries Predominantly Supply the Lung Parenchyma
• Size/Pressure
  • Pulmonary Arteries are Larger Caliber than the Bronchial Arteries
  • Pulmonary Arteries are a Low-Pressure System
    • Consequently, Most Episodes of Hemoptysis Originate from the Pulmonary Arterial Circulation and are Not Life-Threatening
• Anatomy
  • Pulmonary Arteries Originate from the Right Ventricle
• Source of Hemoptysis (see Hemoptysis)
  • The Bronchial Arterial System is the Predominant Source of Hemoptysis in 90% of Cases of Massive Hemoptysis (Crit Care Med, 2000) [MEDLINE]
    • Other Sources Include
      • Pulmonary Arteries (5% of Cases)
      • Non-Bronchial Systemic Arteries (5% of Cases)

Bronchial Arteries

• Function
  • Bronchial Arteries Predominantly Supply the Tracheobronchial Tree, Large Blood Vessels, Lymph Nodes, Esophagus, and Pleura (Radiographics, 2006) [MEDLINE]
    • The Bronchial Arterial Circulation Accounts for Only 2% of the Total Vascular Supply to the Lung
  • Bronchial Arteries are Very Plastic, Potentially Increasing Their Blood Flow from 1% to 30% of the Cardiac Output in Response to a Pulmonary Insult
    • Consequently, Bronchial Artery Hypertrophy and Dilatation of Thin-Walled Distal Bronchial-to-Pulmonary Artery Anastomoses May Occur
• Size/Pressure
  • Bronchial Arteries Have a Smaller Caliber than the Pulmonary Arteries
    • On Contrast-Enhanced CT, They are Very Thin and Difficult to Detect
    • Normal Caliber of the Bronchial Arteries is <1.5 mm Near the Origin and <0.5 mm Distally, as They Branch in the Pulmonary Hila
    • When Bronchial Artery Hypertrophy Occurs, Their Diameter Can Exceed 2 mm, and They Tend to Have a More Tortuous Course
  • Bronchial Arteries are a High-Pressure System (Under Systemic Arterial Pressure)
• Anatomy
  • Orthotopic Origin
    • The Bronchial Arteries Most Commonly Originate from the Descending Thoracic Aorta, Usually at the T5-T6 Vertebral Plane, 1–2 cm Above or Below the Level of the Carina
    • The Orthotopic Right Bronchial Artery Originates Preferentially from the Posteromedial Aortic Wall (Directly or or More Commonly from a Short Intercostal-Bronchial Trunk), Running Retrotracheally Towards the Hilum
    • The Orthotopic Left Bronchial Artery Originates Preferentially from the Anterior or Lateral Aortic Wall, Running Retrotracheally Towards the Hilum
    • Most Patients Have 1-2 Bronchial Arteries on Each Side and a Total of 3-4 Bronchial Arteries
  • Ectopic Origin
    • In Up to 36% of Cases, the Bronchial Arteries Ectopically Originate from Aortic Arch, Subclavian Artery, Thyrocervical Trunk, Internal Mammary Artery, or Coronary Arteries (J Thorac Imaging, 2003) [MEDLINE] (Eur Radiol, 2007) [MEDLINE]
      • Ectopic Bronchial Arteries are Recognized Due to Their Adjacent Course with the Associated Bronchi
  • Bronchial Arteries Have Distal Microvascular Anastomoses Connecting to the Pulmonary Arterial System (Chest, 1972) [MEDLINE]
• Source of Hemoptysis
  • Despite the Bronchial Arteries Accounting for Only 2% of the Total Vascular Supply to the Lung, the Bronchial Arteries are the Predominant Source of Hemoptysis in 90% of Cases of Massive Hemoptysis (Crit Care Med, 2000) [MEDLINE]
    • Other Sources Include
      • Pulmonary Arteries (5% of Cases)
      • Non-Bronchial Systemic Arteries (5% of Cases)

Other Arteries

• The Non-Bronchial Arterial Circulation (Aorta, Intercostal Arteries, Coronary Arteries, Thoracic Arteries, Axillary Arteries, Subclavian Arteries, Upper and Lower Inferior Phrenic Arteries) Can Supply the Lungs in <5% of Cases (Chest, 2008) [MEDLINE] (Respiration, 2010) [MEDLINE]
  • Many Chronic Inflammatory Lung Lesions are Jointly Supplied by Hypertrophied Bronchial Arteries, as Well as by Collateral Systemic Arteries