Dear Martin, thanks VERY much for your reply! This is all an hypothetical scenario for a case study. One more thing, if I may: have you ever used a CO-oximetre, it's a blood gas analyser that you attach to a normal ABG machine but nobody seems to know about. It gives you a breakdown of the various haemoglobins. If I use a normal ABG machine, which gives me SaP02, on a patient with CO intoxication, would that still give me an accurate picture of the patient's pulmonary exchange status after suctioning? Could high levels of carboxyhaemoglobin interfere with the SaO2 readings?