1. Copyright 2008 Society of Critical Care Medicine Mechanical Ventilation 2

2. 1 Copyright 2008 Society of Critical Care Medicine Objectives Describe interactions between ventilatory parameters and modifications needed to avoid harmful effects of mechanical ventilation Review guidelines for initial ventilator management that apply to specific clinical situations

3. 2 Copyright 2008 Society of Critical Care Medicine Case Study 18-year-old found unresponsive at a party (wt 60 kg, ht 64 inches [162.6 cm]) Vomitus in pharynx, difficult intubation SpO2 87-88% on 100% oxygen High pressure alarm sounding What ventilator settings are recommended?

4. 3 Copyright 2008 Society of Critical Care Medicine Case Study Mode FiO2 Tidal volume Rate PEEP Assist control (volume) 1.0 550 mL 10 breaths/min 5 cm H2O ® Predicted body wt = 45.5 + 2.3 (ht in inches-60) = 55 kg

5. 4 Copyright 2008 Society of Critical Care Medicine Case Study SpO2 Blood gas Ppeak Pplat Auto-PEEP Respiratory rate 88% pH 7.38, PaCO2 36 mm Hg (4.8 kPa), PaO2 57 mm Hg (7.6 kPa) 52 cm H2O 48 cm H2O 0 cm H2O 18 breaths/min ® What parameters should be measured?

6. 5 Copyright 2008 Society of Critical Care Medicine Case Study SpO2 88% (FiO2 1.0) Blood gas: pH 7.38, PaCO2 36 mm Hg (4.8 kPa), PaO2 57 mm Hg (7.6 kPa) Ppeak 52 cm H2O Pplat 48 cm H2O Auto-PEEP 0 cm H2O Respiratory rate 18 breaths/min ® What problems are present?

7. 6 Copyright 2008 Society of Critical Care Medicine Case Study Current Ventilator Settings Assist control (volume) FiO2 1.0 Tidal volume 550 mL Respiratory rate 10 breaths/min PEEP 5 cm H2O ® What changes in ventilator settings would improve oxygenation?

8. 7 Copyright 2008 Society of Critical Care Medicine Determinants of Oxygenation FIO2 Mean airway pressure Tidal volume I:E ratio Inspiratory flow rate PEEP Auto-PEEP Inspiratory flow waveform ®

9. 8 Copyright 2008 Society of Critical Care Medicine Case Study Assist control (volume) FiO2 1.0 Tidal volume 550 mL Respiratory rate 10 breaths/min PEEP 5 cm H2O What are the consequences of the following ventilator changes? − Increased PEEP − Increased tidal volume

10. 9 Copyright 2008 Society of Critical Care Medicine Case Study Current Ventilator Settings Assist control (volume) FiO2 1.0 Tidal volume 550 mL Respiratory rate 10 breaths/min PEEP 5 cm H2O ® What changes in ventilator settings would decrease inspiratory plateau pressure?

11. 10 Copyright 2008 Society of Critical Care Medicine Acute Lung Injury Hypoxemic respiratory failure Decreased lung compliance  high airway pressures Lower tidal volume needed (6 mL/kg PBW) Maintain Pplat  30 cm H2O PEEP to improve oxygenation Permissive hypercapnia may be necessary

12. 11 Copyright 2008 Society of Critical Care Medicine Case Study 70-year-old with long smoking history failed NPPV for respiratory distress Intubated, sedated, and receiving mechanical ventilation Wt 75 kg, ht 69 inches [175.3 cm]) Low blood pressure alarm sounding What ventilator settings are recommended?

13. 12 Copyright 2008 Society of Critical Care Medicine Case Study SIMV 1.0 700 mL 12 breath/min 5 cm H2O Mode FiO2 Tidal volume Rate PEEP

14. 13 Copyright 2008 Society of Critical Care Medicine Case Study Blood gas: pH 7.20, PaCO2 60 mm Hg (8 kPa), PaO2 215 mm Hg (28.7 kPa) Pplat 35 cm H2O, Ppeak 50 cm H2O Auto-PEEP 8 cm H2O I:E = 1:1.5 Respiratory rate 18/min Blood pressure 90/60 mm Hg, heart rate 130 beats/min ® What parameters should be measured?

15. 14 Copyright 2008 Society of Critical Care Medicine Case Study Blood gas: pH 7.20, PaCO2 60 mm Hg (8 kPa), PaO2 215 mm Hg (28.7 kPa) Pplat 28 cm H2O, Ppeak 50 cm H2O Auto-PEEP 8 cm H2O I:E = 1:1.5 Respiratory rate 18 breaths/min Blood pressure 90/60 mm Hg, heart rate 130 beats/min ® What are the major problems?

16. 15 Copyright 2008 Society of Critical Care Medicine Case Study Positive intrathoracic pressure Auto-PEEP Hypovolemia Tension pneumothorax Myocardial ischemia ® What are possible causes of the patient’s hypotension?

17. 16 Copyright 2008 Society of Critical Care Medicine Case Study Current Ventilator Settings SIMV FiO2 1.0 Tidal volume 700 mL Respiratory rate 12 breaths/min PEEP 5 cm H2O ® What immediate changes in ventilator settings should be made?

18. 17 Copyright 2008 Society of Critical Care Medicine Case Study SIMV Tidal volume 700 mL Respiratory rate 12 breaths/min PEEP 5 cm H2O pH 7.20, PaCO2 60 mm Hg (8 kPa), PaO2 215 mm Hg (28.7 kPa) Auto-PEEP 8 cm H2O I:E = 1:1.5 ® What are the consequences of the following ventilator changes? − Decrease in tidal volume − Decrease in respiratory rate − Change to assist control (volume)

19. 18 Copyright 2008 Society of Critical Care Medicine Obstructive Airway Disease Initial tidal volume ~8-10 mL/kg Optimize expiratory time Beware of auto-PEEP Adjust minute ventilation to low normal pH Treat obstruction with bronchodilators

20. 19 Copyright 2008 Society of Critical Care Medicine Questions?

21. 20 Copyright 2008 Society of Critical Care Medicine Key Points The complex interactions of ventilator parameters must be appreciated to evaluate the effects in each patient. Primary determinants of oxygenation are FiO2 and mean airway pressure. Patients should be monitored closely during mechanical ventilation. Maintain Pplat  30 cm H2O. Hypotension after initiation of mechanical ventilation should be promptly evaluated.