7th February 2024

Pulmonary circulation

Blood supply to the lung

The lung receives blood supply via bronchial circulation and pulmonary circulation.

Bronchial circulation carries oxygenated blood from the left ventricle and supplies part of the tracheobronchial tree. Bronchial arteries arise from the aorta and the intercostal arteries and drain into pulmonary veins.

Pulmonary circulation carries mixed venous blood from the right ventricle to the pulmonary capillaries, where it participates in gas exchange.

Pressures in the pulmonary circulation

Pulmonary circulation is a low-pressure system. Typical measurements within the main pulmonary artery are:

Mean arterial pressure = 15mmHg

Systolic blood pressure = 25mmHg

Diastolic blood pressure = 8mmHg

Hence, the pressure gradient across pulmonary circulation is around 7-10mmHg.

Pulmonary vascular resistance

To readers familiar with Physics, vascular resistance is analogous to electrical resistance.

Pulmonary vascular resistance is determined by using pressure differences across pulmonary circulation and blood flow rate through the pulmonary circulation.

Pulmonary vascular resistance is approximately one-tenth of the systemic vascular resistance.

References

Levitzky, M. G. (2018). Chapter 4: Blood Flow to the Lung. In Pulmonary physiology (9th ed). McGraw-Hill education.