A 72-year-old man on the medical ward is reviewed because the nurse is worried he is deteriorating. His observations are: temperature 38.9°C, respiratory rate 26/min, oxygen saturation 93% on air, systolic blood pressure 94 mmHg, heart rate 118/min, and he is drowsier than earlier. His National Early Warning Score 2 (NEWS2) is calculated as 7. What is the single most appropriate immediate management step?