Final answer:
Restlessness is an early sign of hypoxemia and is key for nurses to recognize for timely intervention.
Step-by-step explanation:
One of the early signs of hypoxemia, a lower-than-normal level of oxygen in the blood, is restlessness. Restlessness can be an indication of inadequate oxygenation to the brain and other vital organs. It is important for nurses, especially in a pulmonary unit, to recognize restlessness as it may necessitate prompt medical intervention to address potential underlying causes such as pneumonia or respiratory distress syndrome (RDS).