Ventilatory/respiratory failure occurs when

• A. Lungs and respiratory muscles cannot move enough air to adequately oxygenate and remove CO2
• B. Oxygenation is adequate but CO2 removal is excessive
• C. There is only nasal congestion
• D. There is excessive air movement without gas exchange impairment

Answer: (A)

Ventilatory failure happens when the act of moving air into and out of the lungs is not adequate to meet the body's needs for oxygen delivery and CO2 removal. If ventilation is insufficient, less oxygen reaches the blood and CO2 isn’t expelled effectively, leading to hypoxemia and often hypercapnia with possible acidosis.

The best description is the one that states the lungs and respiratory muscles cannot move enough air to adequately oxygenate and remove CO2, because it directly ties together both sides of gas exchange that ventilation controls.

The other scenarios don’t fit: having adequate oxygenation but excessive CO2 removal would imply too much ventilation, not failure; nasal congestion alone doesn’t cause the broad gas-exchange failure seen in respiratory failure; and excessive air movement with no gas exchange impairment means ventilation is working and gas exchange is intact, not a failure.