An eighteen year old man is presented at the emergency department with complaints of dyspnea, weight loss and general unease. You’re the junior intern on call that day and the emergency physician sends you to analyse the blood gas. Will you manage? After watching this SkillsLab video you will for sure! This case-based tutorial, presented by dr. Jos Kooter (internist at the VU University Medical Center in Amsterdam), takes you through the basis of any blood gas.