1. Measuring end-expiratory lung volume Giacomo Bellani, M.D., Ph.D. University of Milano-Bicocca Monza, Italy giacomo.bellani1@unimib.it

2. Conflicts of interest  Personal: Lecturing fees from GE  Institutional, research grants from: Draeger Maquet Chiesi Farmaceutici

3. Which «lung volume» ? Functional Residual Capacity (FRC) Volume of gas in the lung at the end of a physiologic expiration Relaxation volume of respiratory system End Expiratory Lung Volume (EELV) Volume of gas in the lung at end expiration during mechanical ventilation with PEEP EELV @ 0 cmH 2 O= FRC

4. How do we measure End- expiratory lung volume? Why should we measure end-expiratory lung volume?

5. Techniques  CT scan Precise quantitative assessment Radiological exposure+patient transfer  Closed circuit Need for a dedicated tracer+closed system No need for «fast» response concentration measurements - offline measurement  Open circuit muti-breath washin/washout Potentially no need for a gas tracer Fast response measurement, synchrony with tidal ventilation

6. Techniques  CT scan Precise quantitative assessment Radiological exposure+patient transfer  Closed circuit Need for a dedicated tracer+closed system No need for «fast» response concentration measurements - offline measurement  Open circuit muti-breath washin/washout Potentially no need for a gas tracer Fast response measurement, synchrony with tidal ventilation

7. Closed Dilution Technique V f = V i + EELV Mass conservation CiVi FRC ? CfVf Vi Cf Ci ViEELV -= V i * C i = V f * C f

9. Techniques  CT scan Precise quantitative assessment Radiological exposure+patient transfer  Closed circuit Need for a dedicated tracer+closed system No need for «fast» response concentration measurements - offline measurement  Open circuit muti-breath washin/washout Potentially no need for a gas tracer Fast response measurement, synchrony with tidal ventilation

10. 70 % 30 % O2O2 N2N2 50 % FiN 2 =70% VtVt FeN 2 600 ml 1400 ml 1000 ml

11. Multibreath nitrogen washout Wrigge H et al Intensive Care Med 1998; 24: 487 Off-line correction of viscosity effect on sidestream delay time and pneumothacografic measurments

12.  Derives N 2 concentration from: 100%- [CO 2 ]- [CO 2 ]  Uses end-tidal concentration (no need for synchronization)

14. What about Pressure Support ? 0 1000 2000 3000 4000 01000200030004000 EELV by He dilution (ml) EELV by GE Engstrom (ml) Volume Control R 2 = 0.8353 Pressure Support Using a 20% variation in FiO 2 : Bellani G, unpublished

15. FRC INview (Engstrom carestation)

18. How do we measure End- expiratory lung volume? Why should we measure end-expiratory lung volume?

19. EELV is profoundly reduced in ARDS Estimate of alveolar recruitment Determinant of VILI Why should we measure end- expiratory lung volume?

20. EELV is profoundly reduced in ARDS Estimate of alveolar recruitment Determinant of VILI Why should we measure end- expiratory lung volume?

21. Alveolar recruitment by P-V curve Maggiore S. et al, Am J Resp Crit Care Med, 2001

22. Effect of recruitment on FRC (0 cmH 2 O)

23. Patroniti N et al., CCM 2010

24. A simplified approach Assessing alveolar recruitment by EELV PEEP = 0 Compliance=30 ml/cmH2O EELV= 1000 ml PEEP=10 Expected EELV increase: 30 * 10= 300 ml No recruitment EELV= 1300 ml Recruitment EELV = 1600 ml

25. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 4 14 PEEP (cmH2O) EELV (l) 0 5 10 15 20 25 30 35 Crs (ml/cmH2O) 681012 1350 ml Crs 29 expected EELV increase 174 ml 1524 l 1950 l true EELV increase 600 ml ∆EELV / PEEP change = 600 / 6 = 100 ml/cmH2O

28. EELV is profoundly reduced in ARDS Estimate of alveolar recruitment Determinant of VILI Why should we measure end- expiratory lung volume?

29. EELV V E (L/min) RATIO NORMAL ARDS 2500< 7< 2.8 1000> 15 SPECIFIC HYPERVENTILATION

30. Vt/FRC

31. End-expirationEnd-inspiration PET EELV normally-aerated Vt normally-aerated Ki normally-aerated High activity Low activity - 1000 100 -500 Regional distension and inflammation Bellani G et al., Am J Resp Crit Care Med, 2011

32. The role of tidal volume/EELV Bellani G et al., Am J Resp Crit Care Med, 2011

34. Conclusions: o Measurement of end-expiratory lung volume is now available: RESEARCH TOOL → CLINICAL TOOL o Useful in estimating lung recruitment o Can it help in setting PEEP? Yes o Is it being used to set PEEP? Don’t know o Possible role in adjusting tidal volume?