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Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study
Sunny G Nijbroek1, Liselotte Hol, Pien Swart
1From the Department of Intensive Care (SGN, LH, PS, ASN, JMB, MJS), Department of Anaesthesiology, Amsterdam UMC, location AMC, Amsterdam, The Netherlands (SGN, LH, SNTH, MWH), Department of Critical Care Medicine, Australian and New Zealand Intensive Care Research Centre (ANZIC-RC), Monash University, Melbourne, Victoria, Australia (ASN), Hedenstierna Laboratory, Department of Clinical Physiology, Uppsala University Hospital, Uppsala, Sweden (GH), Intensive Care Unit, University Hospital of Montpellier and Saint Eloi Hospital, Montpellier University, Montpellier, France (SJ), Division of Cardiac, Thoracic, Vascular Anaesthesia and Intensive Care, Medical University of Vienna, Vienna, Austria (MH, WS), Operating Services, Critical Care and Anaesthesia, Sheffield Teaching Hospitals, Sheffield and University of Sheffield, Sheffield, UK (GHM), Department of Anaesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA (MFVM), Department of Anaesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany (CP), Department of Biotechnology and Life Sciences, ASST Sette Laghi Ospedale di Circolo e Fondazione Macchi, University of Insubria, Varese, Italy (PS), Department of Anaesthesiology, Intensive Care Medicine and Emergency Medicine, Pain Therapy, Bergmannstrost Hospital Halle, Halle (HW), Department of Anaesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technical University Dresden, Dresden, Germany (MG de A), Dipartimento di Scienze Chirurgiche e Diagnostiche Integrate, Università degli Studi di Genova (PP), IRCCS, Ospedale Policlinico San Martino, Genova, Italy (PP), Mahidol Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Bangkok, Thailand (MJS) and Nuffield Department of Medicine, University of Oxford, Oxford, UK (MJS).
Background:
One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.
Objectives:
The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.
Design, Patients And Setting:
This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.
Main Outcome Measures:
Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.
Results:
This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P < 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P < 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.
Conclusion:
In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.
Trial Registration:
The study was registered at Clinicaltrials.gov, NCT01601223.
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