Cyanosis describes someone's fingertips, toes, hands, or feet turn a shade of blue or green due to a lack of oxygenated blood. Oxygen-rich blood is a bright red inside of an individual's body, while oxygen-poor blood is a dark maroon in the body. Light reflects off of these two colors in different ways, which causes oxygen-poor blood to appear blue when looking at it through the skin. Pulmonary artery sling patients may have trouble with inhaling an adequate amount of oxygen due to the effects pulmonary artery sling has on the function of their trachea and right mainstem bronchus.
Not only can both of those main airways become compressed, but an individual affected by pulmonary artery sling may also experience a decrease in the amount of oxygen they can breathe in due to stenosis, the adaptive narrowing of the trachea or windpipe. Not enough oxygen can reach the alveoli, which causes insufficient levels of oxygen in the blood. Low blood oxygen concentration causes the extremities to exhibit cyanosis.