FCCSslides-05B-MechanicalVent02_Live_2021_20 Sep.pptx

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1. Mechanical Ventilation 2 Copyright 2021 Society of Critical Care Medicine

2. Objectives Describe the interactions between ventilatory parameters Detail the modifications needed to avoid harmful effects of mechanical ventilation Review guidelines for initial ventilator management as they apply to specific clinical situations 1 Copyright 2021 Society of Critical Care Medicine

3. Case Study 1 36-year-old previously healthy (weight 162 lb [73 kg], height 72 inches (183 cm) man; fever for 2 days Admission radiograph: developing infiltrate in left lower lobe Oxygen saturation on pulse oximetry (Sp o 2 ) 83% to 89% on high flow nasal cannula at 10 L/min Repeat radiograph: bilateral infiltrates 2 Copyright 2021 Society of Critical Care Medicine What ventilator settings are recommended?

4. Determinants of Gas Exchange Oxygenation is affected by: Fraction of inspired oxygen (F IO 2 ) Mean airway pressure Ventilation (CO 2 exchange) is affected by: Minute ventilation = respiratory rate x tidal volume 3 Copyright 2021 Society of Critical Care Medicine

5. Determinants of Oxygenation F I O 2 Mean airway pressure Tidal volume Inspiratory to expiratory time (I:E) ratio Positive end-expiratory pressure (PEEP) Inspiratory flow rate Auto-PEEP 4 Copyright 2021 Society of Critical Care Medicine

6. Case Study 1 Mode F I O 2 Tidal volume Rate PEEP Assist-control (volume) 1.0 440 mL 18 breaths/min 5 cm H 2 O 5 Copyright 2021 Society of Critical Care Medicine Predicted body weight = 77.6 kg 50 + (2.3 * [72in – 60]) = 50 + (2.3 * 12) = 77.6 kg

7. Case Study 1 Sp o 2 Blood gas Peak pressure (Ppeak) Plateau pressure (Pplat) Auto-PEEP Respiratory rate 83% pH 7.38, Pa o 2 45 mm Hg (7.6 kPa), Pa co 2 36 mm Hg (4.8 kPa) 52 cm H 2 O 48 cm H 2 O 0 cm H 2 O 18 breaths/min 6 Copyright 2021 Society of Critical Care Medicine Which parameters should be measured?

8. Case Study 1 Sp o 2 83% (F IO 2 1.0) Blood gas: pH 7.38, Pa co 2 36 mm Hg (4.8 kPa), Pa o 2 45 mm Hg (7.6 kPa) Ppeak 52 cm H 2 O Pplat 48 cm H 2 O Auto-PEEP 0 cm H 2 O Respiratory rate 18 breaths/min 7 Copyright 2021 Society of Critical Care Medicine What problems are present?

9. Case Study 1 Current ventilator s ettings Assist-control (volume) F I O 2 1.0 Tidal volume 440 mL Respiratory rate 18 breaths/min PEEP 5 cm H 2 O 8 Copyright 2021 Society of Critical Care Medicine What changes in ventilator settings would improve oxygenation?

10. Case Study 1 Assist-control (volume) F I O 2 1.0 Tidal volume 440 mL Respiratory rate 18 breaths/min PEEP 5 cm H 2 O 9 Copyright 2021 Society of Critical Care Medicine What are the consequences of the following ventilator changes? Increased PEEP Increased tidal volume

11. Acute Lung Injury/Acute Respiratory Distress Syndrome (ARDS) Hypoxemic respiratory failure Decreased lung compliance  high airway pressures Lower tidal volume needed (4 to 6 mL/kg of ideal body weight) Maintenance of Pplat 30 cm H 2 O PEEP to improve oxygenation Permissive hypercapnia may be necessary 10 Copyright 2021 Society of Critical Care Medicine

12. Case Study 2 28-year-old woman with a history of asthma admitted to ICU for acute asthma exacerbation Intubated, sedated, and receiving mechanical ventilation Weight 130 lb (59 kg), height 64 inches (175.3 cm) On admission: Ppeak 40 cm H 2 O, Pplat 25 cm H 2 O; 6 hours later: Ppeak 55 cm H 2 O; Pplat 25 cm H 2 O 11 Copyright 2021 Society of Critical Care Medicine Which ventilator settings are recommended?

13. Case Study 2 Mode F I O 2 Tidal volume Rate PEEP Assist-control (volume) 1.0 400 mL 15 breaths/min 5 cm H 2 O 12 Copyright 2021 Society of Critical Care Medicine

14. Case Study 2 13 Copyright 2021 Society of Critical Care Medicine What is the likely etiology of her high peak airway pressures in the setting of unchanged plateau pressures? In addition to ventilator support, what therapies does this patient need to reduce the elevated airway pressure? Which parameter (Ppeak or Pplat) has been associated with a higher risk of barotrauma in an intubated patient?

15. Case Study 2 Blood gas: pH 7.23, Pa co 2 75 mm Hg (8 kPa), Pa o 2 365 mm Hg (28.7 kPa) Ppeak 55 cm H 2 O, Pplat 25 cm H 2 O, Auto-PEEP 12 cm H 2 O I:E = 1:1.5 Respiratory rate 15 breaths/min Blood pressure 90/50 mm Hg, heart rate 130 beats/min 14 Copyright 2021 Society of Critical Care Medicine What parameters should be measured?

16. Case Study 2 Positive intrathoracic pressure Hypovolemia Myocardial ischemia Tension pneumothorax Auto-PEEP 15 Copyright 2021 Society of Critical Care Medicine What are possible causes of the patient’s hypotension?

17. Case Study 2 Current ventilator settings Assist-control (volume) F I O 2 1.0 Tidal volume 400 mL Respiratory rate 15 breaths/min PEEP 5 cm H 2 O 16 Copyright 2021 Society of Critical Care Medicine What immediate change in ventilator settings should be made?

18. What immediate change in ventilator setting should be made in response to development of auto-PEEP? (Choose the single best answer.) Increase tidal volume. Decrease ventilator rate. Increase ventilator rate. Make no change; the patient will adapt. 17 Copyright 2021 Society of Critical Care Medicine

19. Case Study 2 Current ventilator settings Assist-control (volume) F I o 2 1.0 Tidal volume 400 mL Respiratory rate 15 breaths/min PEEP 5 cm H 2 O 18 Copyright 2021 Society of Critical Care Medicine What immediate change in ventilator settings should be made?

20. Case Study 2 A ssist-control (volume) Tidal volume 400 mL Respiratory rate 15 breaths/min PEEP 5 cm H 2 O pH 7.23, Pa co 2 75 mm Hg (8 kPa), Pa o 2 365 mm Hg (28.7 kPa) Auto-PEEP 12 cm H 2 O I:E = 1:1.5 19 Copyright 2021 Society of Critical Care Medicine What are the consequences of the following ventilator changes? Decrease in tidal volume Decrease in respiratory rate

21. Obstructive Airway Disease Set initial tidal volume approximately 6 to 8 mL/kg Optimize expiratory time Beware of auto-PEEP Adjust minute ventilation to low-normal pH Treat obstruction with bronchodilators Administer steroids and magnesium 20 Copyright 2021 Society of Critical Care Medicine

22. Weaning From Mechanical Ventilation Cause of respiratory failure has improved significantly or resolved Maintain airway, including the ability to clear secretions Adequate oxygen saturation >90%, Po 2 >60 mm Hg, F i o 2 40% to 50% PEEP around 5 to 8 cm H 2 O, pH > 7.25 Able to initiate inspiratory effort Hemodynamically stable and no escalation of resuscitation or vasopressors 21 Copyright 2021 Society of Critical Care Medicine

23. Extubation 22 Copyright 2021 Society of Critical Care Medicine Spontaneous breathing trial (SBT) Negative inspiratory force (NIF) Respiratory shallow breathing index (RSBI)

24. Questions 23 Copyright 2021 Society of Critical Care Medicine

25. Key Points The complex interactions of ventilator parameters must be appreciated to evaluate the effects in each patient. Primary determinants of oxygenation are F I O 2 and mean airway pressure. Patients should be monitored closely during mechanical ventilation. Pplat should be maintained 30 cm H 2 O. Hypotension after initiation of mechanical ventilation should be promptly evaluated. 24 Copyright 2021 Society of Critical Care Medicine