Closed Loop Ventilation

1. Closed Loop Ventilation Vijay Deshpande, MS, RRT, FAARC Emeritus Professor Georgia State University Atlanta, Georgia

2. Evolution of Mechanical Ventilation • Resuscitation Bags • Negative Pressure Ventilation ( Iron Lung etc.) • Pressure Cycled Ventilators ( Bird, Bennett etc.) • Volume Ventilators (Bennett MA-1, Bear 1, Emerson Post-op) • SIMV Ventilators ( Siemens 900 C etc.) • Third Generation Ventilators ( PB 7200, Hamilton Veolar, Bird 6400 etc.) • Microprocessor Ventilators ( Siemens 300, Hamilton Galileo, Bird 8400 ST, Bear 1000 etc.)

3. Technological Advances • Addition of new modes - SIMV, PSV,PCV • Flow Triggering mechanism • Servo Controlled ventilation • Better Alarm System

4. Advancements in Mechanical Ventilation Control, Assist, PEEP, CPAP CLOSED-LOOP VENTILATION VENTILATOR GRAPHICS IMV, SIMV, PSV, PCV, Combinations of Volume or Pressure ventilation: SIMV +PSV, SIMV+PSV+CPAP VAPS, Paug Volume Support, PRVC, Auto-flow, ASV,APV, VS, auto mode PAV, NAVA

5. Flow Triggering Vijay Deshpande

6. Flow Sensor Flow Sensor Flow Triggering

7. Church Bulletin Bloopers Ladies, don't forget the rummage sale. It's a chance to get rid of those things not worth keeping around the house. Don't forget your husbands.

8. ARDS • Acute Respiratory Distress Syndrome • Inflammation leads to Acute Lung Injury • Further deterioration promotes ARDS

9. Etiology of ARDS • Inflammation • Pnemonia • Sepsis • Trauma • Near-drowning

10. ARDS • Inflammatory response promotes: • increased pulmonary vascular permeability • seepage of proteinaceous fluid into the pulmonary interstitium and alveoli • reduction in Surfactant production and inactivation of existing Surfactant • increased surface tension • microatelectasis in the affected areas The American-European Consensus Conference on ARDS. Am J Respir Crit Care Med 1994; 149:818-824

11. Clinical Manifestations of ARDS • Increased Capillary Permeability • Interstitial and intra-alveolar edema • Decreased lung compliance • Atelectasis • Refractory hypoxemia • Bilateral diffuse infiltrates on chest Radiogram • Non-homogeneous disorder on CT scan • Increased PAP with near normal PCWP

13. Saura P, Blanch L. How to set Positive End-Expiratory Pressure. Respir Care 2002; 47 (3): 279-295 Overdistention and repetative opening and closing of alveolar units seem to contribute to progressive lung injury.

14. Factors Responsible for Ventilator-induced lung injury • Lung injury is precipitated by: • Alveolar overdistention than high proximal • airway pressure. • Volutrauma rather than barotrauma

16. Dilemma in Ventilatory Management of ARDS Objective: Reopen collapsed and recruitable alveoli Strategy: Application of Positive Pressure Ventilation Commonly used Mode of Ventilation: Volume Targeted Problem: Alveolar Overdistention

17. VOLUME TARGETED VENTILATION • Delivered Tidal Volume is Constant • Better Control on PaCO2 • Higher risk of Ventilator-induced Lung Injury • Palv may Increase • Potential for local Alveolar Over-distention • May promote patient-ventilator dyssynchrony and increased WOB

18. Surprise!!!!!!!

19. Acute Lung Injury ( ALI ) and ARDS Damage to the Lung : • Not distributed homogenously • Even in severe cases ~ 1/3 lung is open • Open lung receives the entire tidal volume resulting in : • Over-distention • Local hyperventilation • Inhibition of surfactants Ravenscraft, Sue. Respiratory Care, Vol 41, No 2 : 105-111, Feb 1996

22. Over-distention Preset Tidal Volume With little or no change in VT Normal Abnormal Volume (ml) Paw rises Pressure (cm H2O)

23. Over-distention • Observed on a Pressure-Volume Loop • Indicates hyperinflation or excessive application of pressure • May promote Barotrauma • Corrective action includes reduction in the Peak Inspiratory Pressure or Tidal Volume

24. PRESSURE TARGETED VENTILATION • PIP and Palv are Limited • Prevents Alveolar Over-distention • Provides better Patient-Ventilator synchrony • Delivered Tidal Volume depends on Airway Resistance and Lung Compliance • PaCO2 is variable

25. Time-Cycled Flow (L/min) Pressure (cm H2O) Volume (ml) Assisted Mode (Pressure-Targeted Ventilation) Patient Triggered, Pressure Limited, Time Cycled Ventilation Set PC level Time (sec)

26. P P P

27. +PEEP Paw = 1/2 ( PIP- PEEP ) x (TI / TCT) Mean Airway Pressure During constant flow ventilation Mean Airway Pressure can be estimated by: Paw = 1/2 PIP x ( TI / TCT ) If PEEP is added, Paw can be calculated by:

28. MEAN AIRWAY PRESSURE EQUATION: Paw = {[ (Raw x Flow) + VT/2C ]- [PEEP]} x ( TI/TCT ) + PEEP + Auto PEEP

29. What the #%$&@ is this?

30. ARDS network. N Eng J Med 2000, 342(18):1301-1308. Multi-center NIH study demonstrated that ALI/ARDS patients ventilated with tidal volumes of 6 ml/Kg were significantly more likely to survive than those ventilated with tidal volumes of 12 ml/Kg.

32. ARDSnet Findings • Lower Tidal Volumes • Use of rapid rates avoiding auto-PEEP ( < 35/min ) • PPLAT < 30 cm H2O reduces mortality • Lower PPLAT showed better outcome ARDSnet: 6ml/kg reduces mortality vs. 12 ml/kg

33. Strategies to Ventilate ALI and ARDS patients • Prevent Alveolar Over-distention • Use of low Tidal Volumes (5-7 ml/Kg) • May promote de-recruitment of alveoli • Prevent repetitive alveolar opening and closure • Use of Recruitment Maneuver • sustained increase in airway pressure • application of adequate end-expiratory pressure (PEEP/CPAP)

34. Recruiting Maneuver Amato, NEJM 1998; 338-347 • 35-40 cm H2O CPAP for 30-40 seconds • at enrollment • After ventilator discontinuation • Absence of any hemodynamic compromise • No barotrauma

35. Ventilation with Recruitment Maneuver • Sedate the patient (do not paralyze) • Recruit the lung 40 cm H2O for 40 seconds • Continue using Pressure-A/C mode • Perform a decelerating PEEP trials OR set PEEP at 15 cm H2O • Insure vascular volume adequacy • Decrease FIO2 to maintain PaO2 at 60-70 mm Hg Data from Massachusettes General Hospital

36. Efforts made to prevent de-recruitment • Application of PEEP • Use of Inverse Ratio Ventilation with PEEP • Use of Airway Pressure Release Ventilation (APRV) or BiLevel Ventilation

37. How much PEEP?

39. Amato MB., et al., Effect of a protective-ventilation strategy on mortality in ARDS. N Eng J Med 1998;338(6):347-354 Initial recruitment of alveolar units may be achieved by applying PEEP at a level above the lower inflection point of the P-V curve.

40. Lung Protective Strategy Volume (ml) PEEP > 2-3 cm H2O above LIP

41. Lower Inflexion Point ( Pflex) The lower inflection point (Pflex) is obtained by static inflation maneuver and should not be measured from the dynamic curve.

42. Initial PEEP Level 2-3 cm H2O above the Lower Point of Inflection

43. 10 cmH2O No PEEP 800 800 700 700 600 600 500 500 Volume Volume 400 400 300 300 200 Point of Inflection 200 100 100 20 10 0 10 20 30 40 20 10 0 10 20 30 40 Pressure Pressure Optimizing PEEP

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45. COMBINED PRESSURE/VOLUME VENTILATION • Exploit beneficial effects of both Pressure and Volume Ventilation • Improve Patient-ventilator Synchrony • Prevent ventilator induced lung injury

46. Inflection Points Upper Inflection Point Volume (ml) Pressure (cm H2O) Lower Inflection Point (LIP or Pflex)

47. What about Tidal Volume?

48. Inflection Points Upper Inflection Point Volume (ml) Pressure (cm H2O) Lower Inflection Point (LIP or Pflex)

49. Lung Protective Strategy VT above PEEP to reach UIP at end-inspiration Volume (ml) PEEP > 2-3 cm H2O above LIP

50. Lung Recruitment Strategy Lung Recruitment Strategy Volume (ml)