A ventilation/perfusion (V/Q ratio) mismatch occurs when:

ventilation is inadequate due to a traumatic injury or medical condition, which results in an impairment in pulmonary gas exchange.

a disruption in blood flow inhibits the exchange of oxygen and carbon dioxide in the lungs, even though the alveoli are filled with fresh oxygen.

ventilation is compromised, resulting in the accumulation of carbon dioxide in the bloodstream, alveoli, and the tissues and cells of the body.

a traumatic injury or medical condition impairs the body's ability to effectively bring oxygen into the lungs and remove carbon dioxide from the body.