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The actual values in the lung vary depending on the position within the lung. If taken as a whole, the typical value is approximately 0.8. [4] Because the lung is centered vertically around the heart, part of the lung is superior to the heart, and part is inferior. This has a major impact on the V/Q ratio: [5] apex of lung – higher; base of ...
A Pancoast tumor is a tumor of the apex of the lung. It is a type of lung cancer defined primarily by its location situated at the top end of either the right or left lung. It typically spreads to nearby tissues such as the ribs and vertebrae. Most Pancoast tumors are non-small-cell lung cancers.
Local venous pressure falls to -5 at the apexes and rises to +15 mmHg at the bases, again for the erect lung. Pulmonary blood pressure is typically in the range 25–10 mmHg with a mean pressure of 15 mmHg. Regional arterial blood pressure is typically in the range 5 mmHg near the apex of the lung to 25 mmHg at the base.
The left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung. A shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein. The oesophagus may sit in a wider shallow impression at the base of the lung. [3]
The V/Q ratio in the apex is roughly 3.3 and 0.63 in the base, which indicates that perfusion is greater than ventilation towards the base, and the ventilation rate is greater than perfusion towards the apex. [3] Towards the base of the lungs, the fluid volume in the pleural cavity increases due to gravity, resulting in greater intrapleural ...
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Atlas image: lung_carina at the University of Michigan Health System - "Cast of trachea and bronchi, anterior view" (#2) [dead link ] "Trachea and carina — tomogram, coronal plane" at SUNY Downstate Medical Center Archived 2016-03-03 at the Wayback Machine; Carina tracheae entry in the public domain NCI Dictionary of Cancer Terms
In the upright lung, both perfusion and ventilation are greatest at the base, but the gradient of perfusion is steeper than that of ventilation so V/Q ratio is higher at the apex than at the base. This means that blood flowing through capillaries at the base of the lung is not fully oxygenated. [3]