Which of the following indicates potentially serious complications from immobility?

The presence of crackles in the lungs indicates potentially serious complications from immobility. When a person is immobile, fluid can accumulate in the lungs due to stasis and impaired circulation, leading to conditions such as pneumonia or atelectasis. Crackles, which are abnormal lung sounds, can be heard during auscultation and suggest that there may be fluid in the alveoli or that airway obstruction is present. This symptom necessitates further assessment and intervention to prevent serious respiratory complications.

Other options, while they may indicate different health statuses, do not specifically signal complications stemming from immobility. Stable vital signs suggest that the individual is stable and not exhibiting immediate signs of distress, while a persistent cough could have various causes unrelated to immobility. Improved mobility is a positive sign indicating recovery and is opposite to the complications that arise from being immobile. Thus, among the choices, crackles in the lungs are most directly related to the risks associated with prolonged immobility.