High flow or titrated oxygen for obese medical inpatients: A randomised crossover trial

Abstract

Objective: To compare the effects on transcutaneous carbon dioxide tension (PtCO2) of high concentration and titrated oxygen therapy in medical inpatients with morbid obesity who were not selected for a pre-existing diagnosis of obesity hypoventilation syndrome. Design: A randomised, crossover trial undertaken between February and September 2015. Setting: Internal medicine service, Wellington Regional Hospital, New Zealand. Participants: 22 adult inpatients, aged 16 years or more, with a body mass index exceeding 40 kg/m2. Interventions: Participants received in random order two 60-minute interventions, with a minimum 30-minute washout period between treatments: titrated oxygen therapy (oxygen delivered, if required, via nasal prongs to achieve peripheral oxygen saturation [SpO2] of 88e92%), and high concentration oxygen therapy (delivered via Hudson mask at 8 L/min, without regard to SpO2). PtCO2 and SpO2 were recorded at 10-minute intervals. Main outcome measure: PtCO2 at 60 minutes, adjusted for baseline. Results: Baseline PtCO2 was 45 mmHg or lower for 16 participants with full data (73%). The mean difference in PtCO2 between high concentration and titrated oxygen therapy at 60 minutes was 3.2 mmHg (95% CI, 1.3e5.2 mmHg; P = 0.002). Conclusion: High concentration oxygen therapy increases PtCO2 in morbidly obese patients. Our findings support guidelines that advocate oxygen therapy, if required in patients with morbid obesity, be titrated to achieve a target SpO2 of 88e92%. Clinical trial registration: Australian New Zealand Clinical Trials Registry, ACTRN12610000522011.