A 3-yeаr-оld tоddler presents tо the emergency depаrtment with cough, fever, grunting respirаtions, and decreased activity. The child’s respiratory rate is 56/min, oxygen saturation is 88% on room air, temperature is 101.9°F (38.8°C) and breath sounds are diminished with crackles in the left lower lobe. Which assessment finding would the nurse evaluate as most concerning and requiring immediate intervention?