Bronchial artery

The bronchial arteries are the major supply of high-pressure oxygenated blood to the supporting structures of the lung, including the pulmonary arteries, but contribute only 1% of total lung blood flow. Blood in the bronchial circulation does not take part in gas exchange unless there is pathology reducing pulmonary arterial blood supply ^10,11. Two left and one right main bronchial arteries are found in ~70% of patients. 

Summary

• location: posterior mediastinum, in close association with aorta and bronchi

• origin and termination: thoracic aorta (left); common intercostobronchial trunk (right); terminates at capillary plexi of respiratory bronchioles

• branches and supply: variable

• relations: frequently 

Gross anatomy

The bronchial arteries arise from their parent vessels at the T3-T8 levels, most commonly between T5-T6 level (~70%; range 64-80%) where it is termed an orthotopic origin ⁵. There are most commonly 3 main bronchial arteries, one right and two left. In addition, there are often additional smaller bronchial arteries arising from the descending thoracic aorta ⁷.

They are small calibre arteries, with a diameter of 1.5 mm at the origin, tapering down to approximately 0.5 mm at the pulmonary hila level ⁶. 

The main bronchial arteries course into the pulmonary hila, branching down to the level of the respiratory bronchioles ⁷. Proximally, the left bronchial artery passes to the left of the oesophagus, while the right bronchial artery may pass to the right or left of the oesophagus ⁸. Their small branches form a network of arteries running along the external bronchial surface, with penetrating branches to supply the submucosal arterial network and sometimes a subpleural pulmonary capillary plexus ⁷.

Left bronchial arteries

There are usually two left bronchial arteries that arise directly from the anteromedial thoracic aorta ⁸:

• superior left bronchial artery: arises from the aorta near the level of the aortic arch, lateral to the carina, and posterior to the left main bronchus

• inferior left bronchial artery: arises from the aorta parallel to the superior artery, but inferior to the left main bronchus

Right bronchial artery

The right bronchial artery has a common origin with a posterior intercostal artery called the intercostobronchial trunk (ICBT) and arises from the right anteromedial aspect of the thoracic aorta ⁸.

Supply

• trachea and bronchi

• lymph nodes

• visceral pleura (jointly with pulmonary arterial supply ⁷)

• pericardium

• oesophagus (middle-third)

• posterior mediastinum

• vagus nerve

• vaso vasorum of the aorta, pulmonary trunk and pulmonary vein

Variant anatomy

Bronchial artery anatomy is usually classified by the to Cauldwell Classification. 

Origin

Ectopic origin is present in ~20% (range 8.3-35%) of patients and is defined when they arise from the aorta outside of the level from superior endplate of T5 to inferior endplate of T6 ^1,5.

The bronchial arteries may arise from a wide range of arteries including ^1,5:

• aortic arch

• internal thoracic artery

• thyrocervical trunk

• subclavian artery

• coronary arteries

Ostium

Although most commonly arising from the anteromedial aspect of the descending aorta (superomedial aspect aortic arch), the origin may also be located at ⁸:

• anterolateral aorta

• posteromedial aorta

• posterolateral aorta (rare)

Branching patterns

• common bronchial artery trunk (i.e. for both left and right bronchial arteries)

• single bronchial artery bilaterally (i.e. one left and one right)

• single bronchial artery on the left and two bronchial arteries on the right (one ICBT)

• left bronchial artery less commonly has its origin from an ICBT

Related pathology

• haemoptysis

• bronchial artery enlargement

• bronchial arterial aneurysm

• broncho-arterial ratio