The LPN/LVN must be suspecting post operative atelectasis.
Explanation:
Post operative fever in a patient is a common symptom but rales are mostly associated with blocking of air passage. And this blocking of air passage is a common symptom of atelectasis.
Moreover, atelectasis is common in patients who have undergone major surgeries under anesthesia.
Anesthesia changes the rate of lung intake so resulting in collapse of few alveoli.
Thus, it is more probable for the nurse to suspect the development of atelectasis.
