A term newborn (38 weeks gestation) born to a mother with meconium-stained amniotic fluid presents with tachypnea (RR 68/min), grunting, and intercostal retractions within 2 hours of birth. Apgar scores were 8 and 9 at 1 and 5 minutes. Chest X-ray shows patchy infiltrates with hyperinflation and areas of atelectasis. SpO₂ is 88% on room air. What is the most appropriate immediate next step in management?