Cyanosis is also discussed in Chapter 13, The Chest. The important questions regarding cyanosis are indicated in that chapter.

On occasion, cyanosis is noted only in the lower extremities. This is termed differential cyanosis. It is related to a right-to-left shunt through a patent ductus arteriosus (PDA). In a right-to-left shunt resulting from pulmonary hypertension, blood in the pulmonary artery crosses the PDA, which is located below the level of the carotid and left subclavian arteries; deoxygenated blood is pumped only to the lower extremity, producing cyanosis in only that location. Some blood does get to the lungs for oxygenation and is ultimately pumped out through the aorta to produce normal skin color in the upper extremity.

The patient whose feet are shown in Figure 14-11 is a 30-year-old immigrant who was evaluated in the United States for cyanosis. Until the age of 20 years, he had marked ''bluish discoloration'' of his lower extremities and relatively normal color in his upper extremities. Over the next 10 years, there was a gradual darkening of his upper extremities. Note the marked cyanosis of the extremities and nail beds of the fingers and toes. The patient had a PDA with marked pulmonary hypertension.

Differential Cyanosis
Figure 14-11 Differential cyanosis of the extremities: patent ductus arteriosus.
Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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