Measuring end-expiratory lung volume

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: • Lecturingfees from GE • Institutional, researchgrants 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 cmH2O= FRC

4. How do we measure End-expiratory lung volume? • Whyshouldwemeasure end-expiratorylung volume?

5. Techniques • CT scan • Precise quantitative assessment • Radiologicalexposure+patienttransfer • Closedcircuit • Need for a dedicatedtracer+closedsystem • No need for «fast» responseconcentrationmeasurements - offline measurement • Open circuit muti-breathwashin/washout • Potentially no need for a gas tracer • Fast responsemeasurement, synchrony with tidalventilation

6. Techniques • CT scan • Precise quantitative assessment • Radiologicalexposure+patienttransfer • Closedcircuit • Need for a dedicatedtracer+closedsystem • No need for «fast» responseconcentrationmeasurements - offline measurement • Open circuit muti-breathwashin/washout • Potentially no need for a gas tracer • Fast responsemeasurement, synchrony with tidalventilation

7. Ci = - EELV Vi Vi Cf ClosedDilutionTechnique Ci Vi Cf Vf Mass conservation FRC ? Vi* Ci = Vf* Cf Vf = Vi + EELV

9. Techniques • CT scan • Precise quantitative assessment • Radiologicalexposure+patienttransfer • Closedcircuit • Need for a dedicatedtracer+closedsystem • No need for «fast» responseconcentrationmeasurements - offline measurement • Open circuit muti-breathwashin/washout • Potentially no need for a gas tracer • Fast responsemeasurement, synchrony with tidalventilation

10. FeN2 FiN2=70% Vt 30 % 50 % O2 600 ml 1000 ml 70 % N2 50 % 1400 ml 1000 ml

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

12. Derives N2concentration from: 100%- [CO2]- [CO2] • Uses end-tidalconcentration (no need for synchronization)

14. Pressure Support R2 = 0.8353 What about Pressure Support ? Using a 20% variation in FiO2: 4000 Volume Control 3000 EELV by GE Engstrom (ml) 2000 1000 0 0 1000 2000 3000 4000 EELV by He dilution (ml) Bellani G, unpublished

15. FRC INview (Engstrom carestation)

18. How do we measure End-expiratory lung volume? • Whyshouldwemeasure end-expiratorylung volume?

19. Whyshouldwemeasure end-expiratorylung volume? EELV is profoundly reduced in ARDS • Estimate of alveolar recruitment • Determinant of VILI

20. Whyshouldwemeasure end-expiratorylung volume? EELV is profoundly reduced in ARDS • Estimate of alveolarrecruitment • Determinant of VILI

21. Alveolarrecruitment by P-V curve Maggiore S. et al, Am J RespCrit Care Med, 2001

22. Effect of recruitment on FRC (0 cmH2O)

23. Patroniti N et al., CCM 2010

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

25. 1950 l 1524 l Crs 29 expected EELV increase 174 ml true EELV increase 600 ml ∆EELV / PEEP change = 600 / 6 = 100 ml/cmH2O 2 35 1.8 30 1.6 25 1.4 1350 ml 1.2 Crs (ml/cmH2O) 20 EELV (l) 1 15 0.8 0.6 10 0.4 5 0.2 0 0 14 4 6 8 10 12 PEEP (cmH2O)

28. Whyshouldwemeasure end-expiratorylung volume? EELV is profoundly reduced in ARDS • Estimate of alveolarrecruitment • Determinant of VILI

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

30. Vt/FRC

31. Regionaldistension and inflammation End-expiration End-inspiration PET High activity 100 Kinormally-aerated EELVnormally-aerated Vtnormally-aerated -500 Low activity - 1000 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: • Measurement of end-expiratorylung volume isnowavailable: RESEARCH TOOL → CLINICAL TOOL • Useful in estimatinglungrecruitment • Can it help in setting PEEP? Yes • Isitbeingused to set PEEP? Don’tknow • Possiblerole in adjustingtidal volume?