MECHANICAL VENTILATION

1. MECHANICAL VENTILATION D.Gihan Tarabeah Ass. Prof. OF anesthesia And surgical ICU, Mansoura Faculty of Medicine.

2. Presentation • Different settings to consider • Monitoring of the patient • Different type of patient • COPD, Asthma • ARDS • Trouble shooting

3. Ventilator settings

4. Ventilator settings • Ventilator mode • Respiratory rate • Tidal volume or pressure settings • Inspiratory flow • I:E ratio • PEEP • FiO2 • Inspiratory trigger

5. CMV

6. A/CV

7. SIMV

8. PSV(pressure support ventilation) Spontaneous inspiratory efforts trigger the ventilator to provide a variable flow of gas in order to attain a preset airway pressure. Can be used in adjunct with SIMV.

9. Respiratory Rate • What is the pt actual rate demand?

10. Tidal Volume or Pressure setting • Maximum volume/pressure to achieve good ventilation and oxygenation without producing alveolar overdistention • Max cc/kg? = 10 cc/kg • Some clinical exceptions

11. Inspiratory flow • Varies with the Vt, I:E and RR • Normally about 60 l/min • Can be majored to 100- 120 l/min

12. I:E Ratio • 1:2 • Prolonged at 1:3, 1:4, … • Inverse ratio

13. FIO2 • The usual goal is to use the minimum Fio2 required to have a PaO2 > 60mmhg or a sat >90% • Start at 100% • Oxygen toxicity normally with Fio2 >40%

14. Inspiratory Trigger • Normally set automatically • 2 modes: • Airway pressure • Flow triggering

15. Positive End-expiratory Pressure (PEEP) What is PEEP? What is the goal of PEEP? • Improve oxygenation • Diminish the work of breathing • Different potential effects

16. PEEP • What are the secondary effects of PEEP? • Barotrauma • Diminish cardiac output • Regional hypoperfusion • NaCl retention • Augmentation of I.C.P.? • Paradoxal hypoxemia

17. PEEP • Contraindication: • No absolute CI • Barotrauma • Airway trauma • Hemodynamic instability • I.C.P.? • Bronchospasm?

18. PEEP • What PEEP do you want? • Usually, 5-10 cmH2O

19. Monitoring of the patient

20. Look at your patient • Question your pt • Examine your pt • Monitor your pt • Look at the synchronicity of your pt breathing

21. Pressures

22. Compliance pressure (Pplat) • Represent the static end inspiratory recoil pressure of the respiratory system, lung and chest wall respectively • Measures the static compliance or elastance

23. Pplat • Measured by occluding the ventilator 3-5 sec at the end of inspiration • Should not exceed 30 cmH2O

24. Peak Pressure (Ppeak) • Ppeak = Pplat + Pres Where Pres reflects the resistive element of the respiratory system (ET tube and airway)

25. Ppeak • Pressure measured at the end of inspiration • Should not exceed 50cmH2O?

26. Auto-PEEP or Intrinsic PEEP • What is Auto-PEEP? • Normally, at end expiration, the lung volume is equal to the FRC • When PEEPi occurs, the lung volume at end expiration is greater then the FRC

27. Auto-PEEP or Intrinsic PEEP • Why does hyperinflation occur? • Airflow limitation because of dynamic collapse • No time to expire all the lung volume (high RR or Vt) • Expiratory muscle activity • Lesions that increase expiratory resistance

28. Auto-PEEP or Intrinsic PEEP • Auto-PEEP is measured in a relaxed pt with an end-expiratory hold maneuver on a mechanical ventilator immediately before the onset of the next breath

29. Auto-PEEP or Intrinsic PEEP • Adverse effects: • Predisposes to barotrauma • Predisposes hemodynamic compromises • Diminishes the efficiency of the force generated by respiratory muscles • Augments the work of breathing • Augments the effort to trigger the ventilator

30. Different types of patient

31. COPD and Asthma • Goals: • Diminish dynamic hyperinflation • Diminish work of breathing • Controlled hypoventilation (permissive hypercapnia)

32. Diminish DHI • Why?

33. Diminish DHI • How? • Diminish minute ventilation • Low Vt (6-8 cc/kg) • Low RR (8-10 b/min) • Maximize expiratory time

34. Diminish work of breathing • How: • Add PEEP (about 85% of PEEPi) • Applicable in COPD and Asthma.

35. Controlled hypercapnia • Why? • Limit high airway pressures and thus diminish the risk of complications

36. Controlled hypercapnia • How? • Control the ventilation to keep adequate pressures up to a PH > 7.20 and/or a PaCO2 of 80 mmHg

37. Controlled hypercapnia • CI: • Head pathologies • Severe HTN • Severe metabolic acidosis • Hypovolemia • Severe refractory hypoxia • Severe pulmonary HTN • Coronary disease

38. A.R.D.S. Ventilation with lower tidal volume as compared with traditional volumes for acute lung injury and the ARDS The Acute Respiratory Distress Syndrome Network N Engl J Med 2000;342:1301-08

39. Methods • March 96 – March 99 • 10 university centers • Inclusion: • Diminish PaO2 • Bilateral infiltrate • Wedge < 18 • Exclusion • Randomized

40. Methods • A/C 28d or weaning • 2 groups: • 1. Traditional Vt (12cc/kg) • 2. Low Vt (6cc/kg) • End point: • 1. Death • 2. Days of spontaneous breathing • 3. Days without organ failure or barotrauma

41. Results • The trails were stopped after 861 pt because of lower mortality in low Vt group

42. Trouble Shooting

43. Trouble Shooting • Doctor, doctor, his pressures are going up!!! What is your next step?

44. Trouble Shooting • Call the I.T., he will take care of it! • Where is the staff? • I dont know this pt, and run! • Ask which pressure is going up

45. Trouble Shooting • Ppeak is up • Look at your Pplat

46. Trouble Shooting • If your Pplat is high, you are faced with a COMPLIANCE problem • If your Pplat is N, you are faced with a RESISTIVE problem • DD?

47. Trouble Shooting

48. Trouble Shooting • Doctor, doctor, my patient is very agitated! • What is your next step?

49. Trouble Shooting • Give an ativan to the nurse! • Give haldol 10mg to the patient! • Take 5mg of morphine for yourself! • Look at your pt!

50. Trouble Shooting • At the time of intubation, fighting is largely due to anxiety • But what do you do if pt is stable and then becomes agitated?