• Tomas Öhman, Thorir S Sigmundsson, Magnus Hallbäck, Suarez SipmannFernandoF0000-0002-7412-2970Department of Surgical Sciences, Section of Anaesthesiology and Critical Care, Hedenstierna's Laboratory, Uppsala University, Uppsala, Sweden.CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Mad, Mats Wallin, Anders Oldner, Håkan Björne, and Caroline Hällsjö Sander.
• Department of Perioperative Medicine and Intensive Care, Karolinska University Hospital, Stockholm, Sweden.
• Acta Anaesthesiol Scand. 2020 May 1; 64 (5): 670-676.

IntroductionLung protective ventilation can decrease post-operative pulmonary complications. The aim of this study was to evaluate a capnodynamic method estimating effective lung volume (ELV) as a proxy for end-expiratory lung volume in response to PEEP changes in patients, healthy subjects and a porcine model.MethodsAgreement and trending ability for ELV in anaesthetized patients and agreement in awake subjects were evaluated using nitrogen multiple breath wash-out/in and plethysmography as a reference respectively. Agreement and trending ability were evaluated in pigs during PEEP elevations with inert gas wash-out as reference.ResultsIn anaesthetized patients bias (95% limits of agreement [LoA]) and percentage error (PE) at PEEP 0 cm H2 O were 133 mL (-1049 to 1315) and 71%, at PEEP 5 cm H2 O 161 mL (-1291 to 1613 mL) and 66%. In healthy subjects: 21 mL (-755 to 796 mL) and 26%. In porcines, at PEEP 5-20 cm H2 O bias decreased from 223 mL to 136 mL LoA (34-412) to (-30 to 902) and PE 29%-49%. Trending abilities in anaesthetized patients and porcines were 100% concordant.ConclusionThe ELV-method showed low bias but high PE in anaesthetized patients. Agreement was good in awake subjects. In porcines, agreement was good at lower PEEP levels. Concordance related to PEEP changes reached 100% in all settings. This method may become a useful trending tool for monitoring lung function during mechanical ventilation, if findings are confirmed in other clinical contexts.2020 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.

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