Final answer:
The nurse's priority when admitting a 4-month-old infant with heart failure would be to address tachypnea, as it indicates immediate respiratory distress and a potential lack of sufficient oxygen intake.
Step-by-step explanation:
When admitting a 4-month-old infant with heart failure, the nurse's priority finding would be D) Tachypnea. Tachypnea, or rapid breathing, is an immediate concern as it indicates that the infant is working hard to breathe and may not be getting sufficient oxygen, which is vital for survival. As heart failure progresses, the heart struggles to pump blood efficiently, which can lead to fluid buildup in the lungs and thus, difficulty in breathing. Although poor weight gain, a persistent cough, and decreased urine output are also serious findings, they do not represent as immediate a threat to life as tachypnea does.
In a scenario where a baby is born prematurely before type II cells produce sufficient pulmonary surfactant, you would expect b. difficulty inflating the lungs, as surfactant is crucial for keeping the air sacs in the lungs open. In cases of heart failure like the one described, tachypnea can be a result of the heart's inability to pump oxygenated blood effectively.