Final answer:
The prolonged immobility of the client creates a direct risk for Deep Vein Thrombosis (DVT) because immobility can lead to blood stasis and the formation of blood clots in the legs.
Step-by-step explanation:
A 57-year-old client recovering from a bilateral mastectomy and breast reconstruction who is unwilling to mobilize is at risk for several complications due to prolonged immobility. Of the options provided, the client's immobility most directly increases the risk for Deep Vein Thrombosis (DVT). This is because immobility can lead to blood stasis and thus the formation of blood clots in the deep veins of the legs, which can then travel to the lungs, causing pulmonary embolism, a significant and life-threatening complication. Respiratory distress can also be a concern due to poor air exchange from immobility but is not the most direct risk. While immobility can contribute to constipation due to decreased bowel movements and less physical activity, this is not as immediately dangerous as DVT. Immobility does not typically cause an increase in blood pressure; in fact, the lack of movement would more likely contribute to orthostatic hypotension upon mobilization, not increased blood pressure.