Mechanical Ventilation

1. Mechanical Ventilation Michael Hellmann, MD Department of Pulmonary-Critical Care 2.11.2018

2. https://gizmodo.com/the-last-of-the-iron-lungs-1819079169

3. Invasive Mechanical Ventilation • Decision to Intubate • Initiating Mechanical Ventilation • Oxygenation/Ventilation • Ventilator Problems • Decision to Extubate

4. Indications for Mechanical Ventilation • Respiratory Failure • Oxygenation • Ventilation • Trauma or Surgery • Upper Airway Obstruction • Angioedema • Burns, trauma • Airway Protection • Hematemesis • Prevention of Aspiration • Facilitation of Suctioning • Excessive Secretions • Inadequate cough/clearance

5. Rapid Assessment for Intubation Tobin, Martin J. "Principles and practice of mechanical ventilation." (2013).

6. Rapid Assessment for Intubation Tobin, Martin J. "Principles and practice of mechanical ventilation." (2013).

7. Rapid Assessment for Intubation • Patient Appearance vs Lab Data • Chest Imaging, Blood Gasses • pH<7.2, Inability to compensate for acidosis • Worsening airspace disease • Trajectory

8. Mr. Breathless • 65yoM, COPD, new influenza, SOB • Poor appetite, fevers, losing weight: 6’0, 150lbs • Admitted on CPAP, treating influenza, pneumonia, COPD

9. Mr. Breathless • CPAP 8, 100% FiO2, SaO2 84% • ABG: 7.12 / 96 / 52

10. Mr. BreathlessThe decision is made to intubate the 6’0”, 150lb Mr. Breathless. What initial vent settings would be appropriate? • Pressure Control: Inspiratory Pressure 25, PEEP 5, RR 16, FiO2 1.0 • Volume Control: Tidal Volume 750mL, RR 16, PEEP 10, FiO2 0.6 • Pressure Control: Inspiratory Pressure 25, PEEP 10, RR 25, FiO2 0.6 • Volume Control: Tidal Volume 450mL, RR 16, PEEP 10, FiO2 1.0

11. Mr. Breathless • The decision is made to intubate the 6’0”, 150lb Mr. Breathless. What initial vent settings would be appropriate? • A) Pressure Control: Inspiratory Pressure 25, PEEP 5, RR 16, FiO2 1.0 • B) Volume Control: Tidal Volume 750mL, RR 16, PEEP 10, FiO2 0.6 • C) Pressure Control: Inspiratory Pressure 25, PEEP 10, RR 25, FiO2 0.6 • D) Volume Control: Tidal Volume 450mL, RR 16, PEEP 10, FiO2 1.0

12. Low Tidal Volume Strategy ARDS: Berlin Criteria Within one week of known clinical eventBilateral opacities (Not explained by effusion, lobar collapse, or nodules)Respiratory failure not fully explained by heart failure or volume overload PaO2/FiO2 Ratio with PEEP >/= 5: Mild: 200-300 Moderate: 100-200 Severe: <100 • -Timing-Imaging • -Origin of Edema-Oxygenation FOUR CRITERIA

13. Low Tidal Volume Strategy • Dec’d Vent Complications, Ventilatory Days, Organ Failure, Mortality: 39.8% vs 31% • NNT = 12 Acute Respiratory Distress Syndrome Network. "Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome." New England Journal of Medicine 342.18 (2000): 1301-1308.

14. Low Tidal Volume Strategy • Ideal Body Weight: • Male: 50 + 2.3 x (Height inches -60) • Female: 45.5 + 2.3 x (Height inches -60) • Goal Tidal Volume 6mL/kg Ideal Body Weight

15. Ventilation Targets Pressure Control VARIES BY PATIENT Volume Flow SET BY VENT Pressure

16. Ventilation Targets Pressure Control Volume Control SET BY VENT Volume Volume Flow Flow VARIES BY PATIENT Pressure Pressure

17. Ventilation Targets Pressure Volume Advantages Guarantees constant tidal volume Control minute ventilation: pH and PaCO2 Disadvantages Potential for high airway pressures, barotrauma Potential for Dyssynchrony • Advantages • Reduce peak pressures • Patient synchrony • Disadvantages • Potential for hypoventilation • Potential for overdistension

18. Mr. Breathless • Intubated with low tidal volume strategy. • Stabilizes after Intubation, FiO2 weaned

19. Mr. BreathlessThe patient is now oxygenating well, but he has a severe respiratory acidosis. His current ventilator settings are Vt 400, RR 16, PEEP 10, FiO2 0.6. Which intervention would provide the most CO2 elimination? • Bicarbonate infusion • Increase RR from 16 to 20 breaths/minute • Increase Vt from 400 to 500 mL/breath • Increase PEEP from 10 cm H20 to 14cm H20

20. Mr Breathless • The patient is now oxygenating well, but he has a severe respiratory acidosis. His current ventilator settings are Vt 400, RR 16, PEEP 10, FiO2 0.6. Which intervention would provide the most CO2 elimination? • A) Bicarbonate infusion • B) Increase RR from 16 to 20 breaths/minute • C) Increase Vt from 400 to 500 mL/breath • D) Increase PEEP from 10 cm H20 to 14cm H20

21. Oxygenation • Goals: PaO2 55-80, SaO2 >88%

22. Oxygenation • PEEP Lanken, Paul N., et al. Intensive Care Unit Manual E-Book. Elsevier Health Sciences, 2013.

23. Ventilation • Acid-Base Goals: 7.30-7.45 (Tolerate 7.20-7.30) • CO2 Goals: Usually Secondary • Minute Ventilation: Respiratory Rate x Tidal Volume • Alveolar Ventilation: • Deadspace Ventilation

24. Mr. BreathlessYou are called because the patient desaturates even after increasing the FiO2 to 1.0. Breath sounds are present bilaterally but decreased on the left. No wheezing is noticeable. Peak airway pressure has increased to 50 cm H20 (from 30) but plateau pressure is relatively unchanged at 15. Which intervention is MOST LIKELY to improve the patient’s hypoxia? • Air trapping is present, discontinue patient from the ventilator • Secretions are present and need to be suctioned • Pneumothorax is present and requires needle decompression • Pulmonary edema is present requiring diuresis

25. Mr. Breathless • You are called because the patient desaturates even after increasing the FiO2 to 1.0. Breath sounds are present bilaterally but decreased on the left. No wheezing is noticeable. Peak airway pressure has increased to 50 cm H20 (from 30) but plateau pressure is relatively unchanged at 15. Which intervention is MOST LIKELY to improve the patient’s hypoxia? • A) Air trapping is present, discontinue patient from the ventilator • B) Secretions are present and need to be suctioned • B) Pneumothorax is present and requires needle decompression • C) Pulmonary edema is present requiring diuresis

26. Peak vs Plateau Pressure • Volume Control Volume Peak Pressure = Airway Resistance Flow Plateau Pressure = Total Lung Compliance Pressure

27. Peak vs Plateau Pressure Peak Pressure = Airway Resistance Plateau Pressure = Total Lung Compliance Pneumothorax Right Mainstem ET Tube Auto-PEEP Worsening ARDS Pulmonary Edema Pleural Effusions Extrathoracic – Abdominal Pressure • Airway Secretions • Biting the Tube • Bronchospasm • Foreign Body

28. Auto-PEEP • Complete Exhalation Volume Flow

29. Auto-PEEP • COPD: Prolonged, Incomplete Exhalation Volume Flow

30. Auto-PEEP • COPD: Prolonged, Incomplete Exhalation Disconnect Vent, Allow Exhalation Volume Flow

31. Mr. BreathlessBy day 6 the patient has improved greatly. Ventilator FiO2 is weaned to 30%, PEEP is weaned to 5. In the morning his sedation is lessened and he is placed on continuous positive airway pressure of 5. He breathes 30 times a minute with a minute ventilation of 6 liters/minute. What is an appropriate next step? • Extubate to CPAP • Consult for tracheostomy • Resume sedation and re-evaluate the next AM • Start steroids for airway edema

32. Mr Breathless • By day 6 the patient has improved greatly. Ventilator FiO2 is weaned to 30%, PEEP is weaned to 5. In the morning his sedation is lessened and he is placed on continuous positive airway pressure of 5. He breathes 30 times a minute with a minute ventilation of 6 liters/minute. What is an appropriate next step? • A) Extubate to CPAP • B) Consult for tracheostomy • C) Resume sedation and re-evaluate the next morning • D) Start steroids for airway edema

33. Extubation Criteria • Fix Primary Problem? • Is Artificial Airway Required? • Are Lungs Working? • Ventilation • Oxygenation • Lung Mechanics

34. Extubation Criteria • Rapid Shallow Breathing Index • Frequency (f) / Tidal Volume (Vt, in L) • >/=105  Increased risk to fail extubation Increased risk of failure. Yang, Karl L., and Martin J. Tobin. "A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation." New England Journal of Medicine 324.21 (1991): 1445-1450.

35. Extubation Criteria • Are the Lungs Working? • Ventilation: Acid/Base, CO2 elimination • Oxygenation: FiO2 Acceptable? • Can you replicate with non-invasive? Generally </= 0.4 • Lung Mechanics: Rapid Shallow Breathing Index • Daily Spontaneous Breathing Trial: • Daily sedation holiday paired with weaning trial (CPAP of 5) reduced ventilator days and reduced mortality. NNT to save one life = 7 Girard, Timothy D., et al. "Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial." The Lancet 371.9607 (2008): 126-134.

36. Post Extubation CPAP • Planned early NIPPV improves outcomes for marginal extubations • Rescue NIPPV after failing extubation doesn’t work • Future: High flow nasal cannula delivery? Esteban, Andrés, et al. "Noninvasive positive-pressure ventilation for respiratory failure after extubation." New England Journal of Medicine 350.24 (2004): 2452-2460. Nava, Stefano, et al. "Noninvasive ventilation to prevent respiratory failure after extubation in high-risk patients." Critical care medicine 33.11 (2005): 2465-2470.