The document discusses mechanical ventilation strategies for patients with COPD and asthma exacerbations, emphasizing key aspects such as pathophysiology, determinants of Paco2, and the role of NIPPV in treatment. It highlights the impact of factors like auto-peep, work of breathing, and ventilator settings on patient outcomes. Recommendations include using low tidal volumes and appropriate PEEP to manage ventilation effectively.

1. Mechanical Ventilation of Patients with COPD and Asthma Richard K. Albert, M.D. Chief of Medicine Denver Health Professor of Medicine University of Colorado Adjunct Professor of Engineering and Computer Science University of Denver 8 th Pulmonary Medicine Update February 7, 2008 Denver Health

2. Colorado Aspen Trees Denver Health

3. Colorado Aspen Trees Denver Health

4. Mechanical Venitlation of COPD & Asthma Exacerbations Objectives  Pathophysiology - PaCO 2 dederminants - Gas trapping - Work of breathing - Auto-PEEP  NIPPV - IPAP - EPAP  Mechanical ventilation - FIO 2 - PEEP - V T Denver Health

5. Pathohysiology of Asthma/COPD Exacerbations PEEP IPAP MV? Steroids Abx? MV? BDs Airway Inflammation Airway narrowing & obstruction Shortened muscles,  curvature  Frictional WOB  muscle strength  V T PaCO 2 pH PaO 2 Gas trapping Auto- PEEP  VCO 2  V E  Elastic WOB  V A IPAP MV Denver Health

6. Determinants of PaCO 2 PaCO 2  VCO 2 V A  VCO 2   Work - Agitation - Seizures -  WOB   Metabolism - Fever - CHO -  T4  V A   V E -  RR -  V T -  V D (without  V E ) Denver Health

7. Oxygen Cost of Breathing Roussos, JCI 1959 Denver Health

8. PV Curve in COPD and Asthma (Stable) Macklem and Becklake, 1963 -10 -20 -30 -40 2 4 6 Ptp (cm H 2 O) V L (L) V T V T Normal/ Asthma Emphysema Denver Health

9. COPD CXR Denver Health

10. PV Curve in COPD & Asthma (Acute Exacerbtion) -10 -20 -30 -40 2 4 6 Ptp (cm H 2 O) V L (L) V T V T Asthma Emphysema Denver Health

11. Implication V T falls because FRC encroaches on TLC  Limited ability to  V T with MV/IPAP Best way to  PaCO 2 is to  VCO 2   WOB (frictional and/or elastic)   PaCO 2 even if V T , V E and V A are constant Denver Health

12. Gas Trapping  P Inspmax Lung Volume TLC RV P Inspmax -100 0 Respiratory muscle weakness (Not fatigue!) Denver Health

13. Effect of Auto-PEEP Patm = 0 P A = 0 Ppl = - 5 Normal airway resistance (end-exhalation) Pel = 5  Ppl needed to initiate inhalation: - 1 P A drops to - 1 relative to Patm - 5 - 5 Ptp = 5 Denver Health

14. Effect of Auto-PEEP P A = 10 Airway narrowing causing auto-PEEP P atm = 0 Ppl = 2 Pel = 8  Ppl needed to initiate inhalation: - 11 2 2 Ptp = 8 Denver Health

15. Treatment of Auto-PEEP with PEEP or CPAP Airway narrowing with auto-PEEP: Treatment with PEEP P A = 10 PEEP = 10 Ppl 2 Pel = 8  Ppl needed to initiate inhalation: - 1 The only thing PEEP does is  work of breathing 2 2 Ptp = 8 Denver Health

16. Implication PEEP, EPAP, CPAP  No effect on V E , V T or V A   WOB (elastic) -  VCO 2 (on next breath) -  PaCO 2 (on next breath) Denver Health

17. Treatment of Auto-PEEP with  V insp Longer time for exhalation, P A falls P A = 6 Ppl = 1 Pel = 6  Ppl needed to initiate inhalation: - 7 1 1 Ptp = 5 P atm = 0 Denver Health

18. Work of Breathing Work of Breathing RV FRC TLC Total Work Elastic Work Frictional Work Denver Health

19. EPAP or CPAP vs IPAP Appendini, AJRCCM 1994  Ptp, Ptd in 7 COPD pts within 48 hrs  Work of breathing measured during: - Spontaneous breathing - CPAP = 0.8 - 0.9 auto-PEEP - PS = 10 cm H 2 O - PS + CPAP  Both CPAP and PS  WOB ¯  Additive  ? effect of underestimating auto-PEEP Denver Health

20. NIPPV Pathophysiology of AECOPD & Asthma is amenable to Rx with NIPPV  EPAP for auto-PEEP   IPAP for inspiratory Raw Will  work of breathing   VCO 2  At constant V A ,  PaCO 2 and  pH May  V A May  mortality and intubation rate Denver Health

21. Frequency of Intubation in Controls in Studies of NIPPV Study N % Kramer, 1995 15 73 Wysocki,1995 20 70 Brochard. 1995 42 74 Burk, 1973 ? 29-54 Albert, 1980 44 2 Bone, 1984 50 26 Niewoehner, 1999 271 3 Denver Health

22. Mortality in Controls in Studies of NIPPV Study N % Bott, 1993 30 30 Kramer, 1995 15 13 Wysocki,1995 20 50 Brochard. 1995 42 29 Sukumalchantra, 1966 43 18 Campbell, 1967 198 6 Albert, 1980 44 0 Stauffer, 1993* 67 19 Niewoehner, 1999 271 3 Denver Health

23. Mechanical Ventilation of COPD & Asthma Exacerbations Mode:  AC vs IMV  PS  ? rest respiratory muscles: CMV  Better sleep with AC vs. IMV-PS  Ventilator-induced diaphragm changes (?) Triggering: key issue with either mode  PEEP to counter auto-PEEP  Major cause of patient-ventilator dissynchrony Denver Health

24. Mechanical Ventilation of COPD & Asthma Exacerbations Tidal Volume (with AC)  Recommendations: 8-12 ml/kg  For 60 kg man = 480 to 720 ml  Frequently > FEV 1 !  Use smaller V T (encroaching on TLC) Minimize effect of auto-PEEP  High inspiratory flow ( ignore peak Paw)  PEEP Adjust ventilator to patient, not vice-versa Denver Health

25. V/Q in Emphysema (H-Pattern): Normal and High V/Q Wagner, JCI 1977 0 0.001 0.01 1 10 100 0 0.1 0.2 0.3 0.4 0.5 V/Q Ratio Ventilation ( ) Perfusion ( ) Denver Health

26. V/Q in Emphysema (L-Pattern): Normal and Low V/Q 0 0.001 0.01 1 10 100 0 0.1 0.2 0.3 0.4 0.5 V/Q Ratio Wagner, JCI 1977 Ventilation ( ) Perfusion ( ) Denver Health

27. Effect of V A /Q on PaCO 2 (Normal) VCO 2 = 100 ml/min PcCO 2 = 40 PaCO 2 = 40 PcCO 2 = 40 PvCO 2 = 46 PvCO 2 = 46 DCO 2 = 100 ml/min DCO 2 = 100 ml/min P A O 2 = 100 P A CO 2 = 40 P A O 2 = 100 P A CO 2 = 40 VCO 2 = 100 ml/min Denver Health

28. Effect of V A /Q on PaCO 2 (Low V A /Q, Normal) PcCO 2 = 40 PaCO 2 = 40 PcCO 2 = 40 PvCO 2 = 46 DCO 2 = 50 ml/min DCO 2 = 150 ml/min HPV 50%  V E VCO 2 = 50 ml/min 50%  V E VCO 2 = 150 ml/min PvCO 2 = 46 P A O 2 = 50 P A CO 2 = 40 P A O 2 = 100 P A CO 2 = 40 Denver Health

29. Effect of V A /Q on PaCO 2 (Low V A /Q,, AECOPD) PcCO 2 = 44 PaCO 2 = 42 PcCO 2 = 40 PvCO 2 = 46 PvCO 2 = 46 DCO 2 = 50 ml/min HPV V E at max 50%  V E VCO 2 = 50 ml/min VCO 2 = 100 ml/min DCO 2 = 150 ml/min P A O 2 = 50 P A CO 2 = 40 P A O 2 = 100 P A CO 2 = 40 Denver Health

30. Effect of V A /Q on PaCO 2 (Low V A /Q,, AECOPD,  F I O 2 ) PcCO 2 = 44 PaCO 2 = 44 PcCO 2 = 44 PvCO 2 = 46 PvCO 2 = 46 DCO 2 = 100 ml/min HPV V E constant 50%  V E VCO 2 = 50 ml/min VCO 2 = 50 ml/min DCO 2 = 100 ml/min  FIO 2 P A O 2 = 100 P A CO 2 = 44 P A O 2 = 100 P A CO 2 = 44 Denver Health

31. Acute Exacerbations of COPD What do I do?  NIPPV with EPAP - Auto-PEEP - Work of breathing - VCO 2  Mechanical ventilation - PEEP to facilitate triggering - Low V T - Lowest safe FIO 2 Denver Health

32. Acute Exacerbations of COPD Summary  Pathophysiology - VCO 2 - Gas trapping - Work of breathing - Auto-PEEP  NIPPV - IPAP - EPAP  Mechanical ventilation - FIO 2 - PEEP - V T Denver Health

33. 8 th Pulmonary Medicine Update February 6, 2008 Denver Health