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

Janine Pilcher, Michael Richards, Leonie Eastlake, Steven J McKinstry, George Bardsley, Sarah Jefferies, Irene Braithwaite, Mark Weatherall and Richard Beasley
Med J Aust 2017; 207 (10): 430-434. || doi: 10.5694/mja17.00270

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 88–92%), 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, 1.3–5.2 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 88–92%.

Clinical trial registration: Australian New Zealand Clinical Trials Registry, ACTRN12610000522011.

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  • Janine Pilcher1
  • Michael Richards1
  • Leonie Eastlake1
  • Steven J McKinstry1
  • George Bardsley1
  • Sarah Jefferies1
  • Irene Braithwaite1
  • Mark Weatherall2
  • Richard Beasley1

  • 1 Medical Research Institute of New Zealand, Wellington, New Zealand
  • 2 Wellington School of Medicine, University of Otago, Wellington, New Zealand


Acknowledgements: 

This study was funded by the Health Research Council of New Zealand (HRC). Janine Pilcher and Irene Braithwaite received HRC clinical training fellowships (12/879, 14/040). The Medical Research Institute of New Zealand receives funding from the HRC Independent Research Organisations Capability Fund (14/1002). The HRC had no involvement in the design of the study, collection, analysis or interpretation of the data, nor in the decision to submit the results for publication.

Competing interests:

Janine Pilcher, Michael Richards, Leonie Eastlake and Richard Beasley are members of the Thoracic Society of Australia and New Zealand Adult Oxygen Guidelines Group. Richard Beasley is a member of the BTS Emergency Oxygen Guideline Group.

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