Results Titrated O 2 reduced mortality compared with high flow O 2 by 58% for all patients (RR 0.42, 95%CI 0.20 to 0.89; P=0.02) and by 78% for the patients with confirmed COPD (RR 0.22, 95%CI 0.05 to 0.91; P=0.04) Patients with COPD who received titrated O 2 according to the protocol were significantly less likely to have respiratory acidosis (mean difference in pH 0.12 (SE 0.05); P=0.01; n=28) or hypercapnia (mean difference in arterial carbon dioxide pressure 33.6 (16.3) mm Hg; P=0.02; n=29) than were patients who received high flow O 2 Number needed to harm by using high flow O 2 =14 (9%-2%=7%; 100/7=14)
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