Final answer:
Respiratory acidosis in a neonate with respiratory distress syndrome is confirmed when the laboratory report reveals an increased PaCO2 of 55 mm Hg.
Step-by-step explanation:
Respiratory acidosis in a neonate with respiratory distress syndrome is confirmed when the laboratory report reveals an increased PaCO2 of 55 mm Hg. The other options listed (pH of 7.35, potassium level of 0.6 mEq/L, arterial O2 pressure of 80 mm Hg) are not specific indicators of respiratory acidosis.