1. Evaluation of lung and chest wall mechanics during anaesthesia using the PEEP-step method 
P. Persson, O. Stenqvist, S. Lundin 
British Journal of Anaesthesia 
Volume 120, Issue 4, Pages (April 2018)
DOI: /j.bja
Copyright © 2017 The Authors Terms and Conditions

2. Fig 1
PEEP-step method (PSM) measurement sequence: 1. Baseline ventilation. 2. Increased PEEP≈0.7×airway driving pressure (ΔPAW) at baseline. Determine the change in end-expiratory lung volume (ΔEELV) during 60–90 s at the new PEEP level. 3. Change PEEP back to baseline level after 120 s. Determine ΔEELV during 60–90 s. 4. Set tidal volume (VT)=mean ΔEELV. Calculate lung elastance as change in PEEP divided by change in end-expiratory lung volume (EL=ΔPEEP/mean ΔEELV) and transpulmonary driving pressure as lung elastance multiplied by tidal volume (ΔPL=EL×VT).
British Journal of Anaesthesia  , DOI: ( /j.bja )
Copyright © 2017 The Authors Terms and Conditions

3. Fig 2
Comparison of calculated and measured change in end-expiratory lung volume (ΔEELV) after an increase in PEEP. For calculated change in EELV (ΔPEEP/ELCONV)), the lung elastance from oesophageal measurements (ELCONV) is used (ELCONV=ΔPAW–ΔPES/tidal volume). Values from first, second, and third PEEP steps are marked with green, grey, and red dots, respectively.
British Journal of Anaesthesia  , DOI: ( /j.bja )
Copyright © 2017 The Authors Terms and Conditions

4. Fig 3
Transpulmonary driving pressure (ΔPLCONV) correlated to change in positive end-expiratory pressure (ΔPEEP) with a line of equality. During measurement of transpulmonary driving pressure (ΔPLCONV=ΔPAW–ΔPES), the size of the tidal volume is set equal to the measured change in end-expiratory lung volume (ΔEELV) induced by the change of PEEP (ΔPEEP). Values from first, second, and third PEEP steps marked with green, grey, and red dots, respectively.
British Journal of Anaesthesia  , DOI: ( /j.bja )
Copyright © 2017 The Authors Terms and Conditions

5. Fig 4
Change in positive end-expiratory pressure (ΔPEEP) compared to transpulmonary driving pressure (ΔPLCONV) for a tidal volume equal to the PEEP-induced change in end-expiratory lung volume (VT=ΔEELV). Values divided into three groups according to the size of the PEEP-induced change in end-expiratory lung volume and corresponding tidal volume. Bars in diagram represent mean values presented with standard deviation.
British Journal of Anaesthesia  , DOI: ( /j.bja )
Copyright © 2017 The Authors Terms and Conditions

6. Fig 5
Difference between the transpulmonary driving pressure calculated by the conventional method (ΔPLCONV=ΔPAW–ΔPES) and the PEEP step method (ΔPLPSM=ELPSM×VT) plotted against the mean value according to Bland and Altman. All measurements from each PEEP step are included. Values from first, second, and third PEEP step are marked with green, grey, and red dots, respectively. Mean difference (bias) indicated with a solid line and limits of agreement (±2 SD) with dashed lines in corresponding colours.
British Journal of Anaesthesia  , DOI: ( /j.bja )
Copyright © 2017 The Authors Terms and Conditions