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

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

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

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

Rapid Assessment for Intubation Clinical Signs of Increased WOB: Facial Appearance: Mouth open during inspiration, tongue jerking. Pursed Lip Breathing during exhalation Speech: Reduced to yes/no questions, unable to speak in full sentences? Mentation: Early – Anxious, Late – vacant gaze, apathy, then drowsiness, and coma. Tobin, Martin J. "Principles and practice of mechanical ventilation." (2013).

Rapid Assessment for Intubation Accessory Muscle Usage Nasal Flaring: Reduces nasal resistance 40-50%, Reduces airway resistance 10-30%. Prominent Sternomastoid Muscles. Chest wall pulling cricoid cartilage down Intercostal Recessions Respiratory Rate: Tachypnea is nearly universally found in respiratory distress Tobin, Martin J. "Principles and practice of mechanical ventilation." (2013).

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

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

Mr. Breathless CPAP 8, 100% FiO2, SaO2 84% ABG: 7.12 / 96 / 52 Not expiring CO2 CPAP 8, 100% FiO2, SaO2 84% ABG: 7.12 / 96 / 52

Pressure Control: Inspiratory Pressure 25, PEEP 5, RR 16, FiO2 1.0 Mr. Breathless The 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 D

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

Low Tidal Volume Strategy ARDS: Berlin Criteria FOUR CRITERIA -Timing -Imaging -Origin of Edema -Oxygenation Within one week of known clinical event Bilateral 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

Low Tidal Volume Strategy Dec’d Vent Complications, Ventilatory Days, Organ Failure, Mortality: 39.8% vs 31% NNT = 12 ARDS – better outcomes with low tidal volumes 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.

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

Ventilation Targets Pressure Control VARIES BY PATIENT Volume Flow Pressure is Set (Independent) Volume is Variable (Dependent) on the interaction of the ventilator and the patient’s lung compliance and airflow resistance. Pressure SET BY VENT

Ventilation Targets Pressure Control Volume Control SET BY VENT Volume Flow Flow Pressure is Set (Independent) Volume is Variable (Dependent) on the interaction of the ventilator and the patient’s lung compliance and airflow resistance. VARIES BY PATIENT Pressure Pressure

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

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

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? 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 C

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

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

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

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

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? 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 B

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

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

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

Auto-PEEP Complete Exhalation Volume Flow

Auto-PEEP COPD: Prolonged, Incomplete Exhalation Volume Flow

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

Consult for tracheostomy Resume sedation and re-evaluate the next AM 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? Extubate to CPAP Consult for tracheostomy Resume sedation and re-evaluate the next AM Start steroids for airway edema C

Mr Breathless A) Extubate to CPAP B) Consult for tracheostomy 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

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

Extubation Criteria Rapid Shallow Breathing Index Frequency (f) / Tidal Volume (Vt, in L) >/=105  Increased risk to fail extubation RSBI = RR/TV(mL); RSBI goal <105 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.

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.

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? Nava, Stefano, et al. "Noninvasive ventilation to prevent respiratory failure after extubation in high-risk patients." Critical care medicine 33.11 (2005): 2465-2470. Esteban, Andrés, et al. "Noninvasive positive-pressure ventilation for respiratory failure after extubation." New England Journal of Medicine 350.24 (2004): 2452-2460.