BY: DR. AHMED S. EL-KOMI, MD Specialist of Anaesthesia & ICU Farwaniya Hospital

1. PRINCIPLES OFMECHANICAL VENTILATION BY: DR. AHMED S. EL-KOMI, MD Specialist of Anaesthesia & ICU Farwaniya Hospital

3. Introduction • Cornerstone for intensive care medicine • The ventilators must overcome the pressure generated by the elastic recoil of the lung at end inspiration plus the resistance to flow at the airway. • Ventilators provide infusion of a blend of air or oxygen into the circuit.

4. History • In 1543, Vesalius demonstrated the ability to maintain the beating heart in animals with open chest. • In 1780, such technique were first applied to humans • In 1887, fell-o-dwyer apparatus was used for translaryngeal ventilation via a bellows. • In 1928, the drinker–Shaw iron lung based on negative pressure ventilation • From 1930-1950 – such machines were the mainstay in ventilation of victims of polio epidemics

5. Drinker-Shaw iron lung

6. MECHANICAL VENTILATION • Objectives • Clinical conditions need ventilator support • Physiological effects • Types • Complications • Monitoring • Weaning

7. Objectives

8. It is the volume remaining after normal expiration • Act as an oxygen reserve  maintain oxygenation of blood passing the lung during expiration / breath holding. (PAO2 decreased by 3 mmHg during expiration) What is the definition of FRC ??

9. Clinical conditions need ventilator support

10. Physiological effects Cardiovascularsystem Positive pressure ventilation results in: Rise in pleural pressure Rise in intra-abdominal pressure Increased lung volumes All these produce cardiovascular changes

11. Physiological effects Preload LV preload reduced by a variety of mechanisms Venous return • In a volume resuscitated patient venous return does not fall • Intrathoracic pressure is positive rather than negative but • Intra-abdominal pressure also rises • Pressure gradient between abdomen and thorax is maintained

12. Physiological effects • In a volume depleted patient Positive pressure intrathoracic Collapse of intra-abdominal veins and SVC • Abdomen collapse behind the liver as a result of positive pleural pressure transmitted through the diaphragm and liver • Superior vena cava results in a fall in venous return • RV stroke volume and hence LV preload

13. Physiological effects • Renal • Renal blood flow falls if cardiac output falls • Decreased sodium secretion due to fall in cardiac output and decreased secretion of atrialnatriuretic factor • Increased water retention due to increased secretion of ADH, particularly in children. • CNS Increased intrathoracic pressure decreases venous drainage from head and may increase ICP.

14. MECHANICAL VENTILATION • Non-invasive ventilation • Invasive ventilation

15. Non-invasive ventilation • Indications • Decreased ventilation • Increased work of breathing • Post-extubation for some COPD patients • Types • Face mask / Nasal cannula • Non-invasive mechanical ventilation

16. Non-invasive ventilation Non-invasive mechanical ventilation • BiPAP • Bi-level CPAP • Two pressure levels (PH & PL) • IPAP (PH) • EPAP (PL) • Delivered by nasal or full face mask

17. Non-invasive ventilation • Advantages • Avoids intubation • Preserves lower airways defense mechanisms  decrease noso-comial infection (Pneumonia or sinusitis) • Decreases patient’s discomfort • Preserves speech and swallowing • Decreases the amount of sedation • Allows application of therapy intermittently • Decreases the work of breathing  • Hypocarbia •  O2 Consumption

18. Non-invasive ventilation • Disadvantages • Limited access for airway management • Mask  discomfort and complications • Leaks  inadequate ventilation • Needs alert and cooperative patient • Contraindications: • Facial deformity / fracture • Inability to protect airway • Excessive secretion • Decreased mental status • Hemodynamic instability

19. Invasive Ventilation • With Intubation • Mechanical ventilation • T-piece tube What is a breathing machine (mechanical ventilator)? • A breathing machine helps the patient breathe. • It is designed to help patients who cannot breathe adequately on their own. • The breathing machine does not fix any problems of the lungs. • It is a device that simply pushes air and oxygen into the lungs and withdraws carbon dioxide from the lungs. • The lungs must function in order for the breathing machine to be effective

20. Invasive Mechanical Ventilation INDICATIONS

21. Invasive Mechanical Ventilation INDICATIONS

22. Invasive Mechanical Ventilation INDICATIONS

23. Ventilator cycle

24. Invasive Mechanical Ventilation CLASSIFICATIONS OF MECHANICAL VRNTILATORS

25. Components • Bacterial filter • Pneumotachometer, valves & solenoids • Humidifier • Heater/ theremostat • Oxygen analyser • Pressure manometer • Chamber for nebulising drug

26. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) • Respiratory Rate (RR) • Inspiratoty Oxygen Fraction (FiO2) • I:E Ratio • Inspiratory Flow Rate (IFR) • Trigger Sensitivity • PEEP

27. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) preset at 7-10 ml/Kg

28. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) • Respiratory Rate (RR) • If the patient is clinically stable  8-14 breath/min • Restrictive lung disease RR • Chronic respiratory acidosis  RR • Too high RR  Respiratory alkalosis - barotraumas • Too low RR hypoventilation -  work of breathing

29. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) • Respiratory Rate (RR) • Inspiratoty Oxygen Fraction (FiO2) Adjusted according to ABG within 20-30 min to keep SaO2 > 90% and PaO2 > 60mmHg • I:E Ratio Normally 1:2 - in ARDS: IRV 2:1

30. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) • Respiratory Rate (RR) • Inspiratoty Oxygen Fraction (FiO2) • I:E Ratio • Inspiratory Flow Rate (IFR) = tidal volume/inspiratory time Vt/Ti set at 40-90 L/min • High IFR ≥ 90 L/min • Used in COPD to increase Te AutoPEEP • Disadvantages: PIP risk of barotrauma • Low IFR ≤ 40 L/min • Used in ARDS to avoid PIP and risk of barotraumas • AutoPEEP

31. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) • Respiratory Rate (RR) • Inspiratoty Oxygen Fraction (FiO2) • I:E Ratio • Inspiratory Flow Rate (IFR) • Trigger Sensitivity Determines start of inspiration Pressure set at -0.5 to 2.0 • -0.5  too sensitive  self cycling • -2.0  too insensitive  work of breathing

32. Invasive Mechanical Ventilation INITIAL VENTILATOR SETTINGS • Tidal Volume (Vt) • Respiratory Rate (RR) • Inspiratoty Oxygen Fraction (FiO2) • I:E Ratio • Inspiratory Flow Rate (IFR) • Trigger Sensitivity • PEEP • Positive end-expiratory pressure • Holds alveolar sacs open and recruits more alveoli • Preset (physiological) = 3-5 cmH2O

33. Invasive Mechanical Ventilation AVOID CHANGING MORE THAN ONE VENTILATOR PARAMETER AT A TIME

34. Invasive Mechanical Ventilation Your patient acutely develops inadequate alveolar ventilation despite correct alveolar settings What causes must you rapidly rule out? LIFE

35. Invasive Mechanical Ventilation LIFE

36. Invasive Mechanical Ventilation MODES OF MV • A/C Assisted Control • SIMV Synchronized IMV • PSV Pressure Support Vent.

37. Invasive Mechanical Ventilation MODES OF MV • A/C Assisted Control • Volume controlled mode (preset Vt + RR) • The ventilator senses any patient-generated resp. effort and intermediately follows with a full machine-powered breath • Little patient’s work of breathing • Respiratory alkalosis is common

38. Invasive Mechanical Ventilation MODES OF MV • SIMV Synchronized IMV • The ventilator senses the patient’s spontaneous breath and times the machine-delivered breaths with the patient’s breathing cycle • SIMV prevents breaths stacking

39. Which is the best ventilation mode for each of the following clinical scenarios ? • A trauma patient who is totally apneic • ARDS patient with very low lung compliance • 24HRS P’ laporotomy with spont. breaths SIMV A/C PCV

40. Which is the best ventilation mode for each of the following clinical scenarios ? • A trauma patient who is totally apneic • ARDS patient with very low lung compliance • 24HRS P’ laporotomy with spont. breaths SIMV A/C PCV

41. Invasive Mechanical Ventilation COMPLICATIONS • RESPIRATORY: • Hypo or hyperventilation • Complications of excessive pressure and flow rates • Pulmonary barotraumas • Pulmonary volutrauma • Patient/ventilator asynchrony • Ventilator malfunction • Ventilator associated pneumonia • Complications of tracheal intubation

42. Invasive Mechanical Ventilation COMPLICATIONS • CVS: Effects of  ITP and PEEP •  Cardiac output •  Hepatic blood flow •  RBF •  ICP • OXYGEN TOXICITY: • GIT: • GIT bleeding • GIT colonization

43. Invasive Mechanical Ventilation COMPLICATIONS • RENAL: UOP • NUTRITIONAL: •  Caloric requirements •  PaCO2 • PSYCHOLOGICAL TRAUMA: • ADJUVANT DRUGS SIDE EFFECTS: • Morphine • Benzodiazepines • NMBs

44. Monitoring • Clinical • Radiological • Biochemical • Bacteriological • others

45. Clinical monitoring General Appearance • Level of activity • Response to stimulus • Eye opening • Posture • Perfusion • Color • Edema

46. Clinical monitoring Adequacy of mechanical breath • Movement of chest • Retractions • Synchronization • Air entry

47. Clinical monitoring Monitoring of O2 & CO2 status • Pulse oximetry • EtCO2 monitoring • ABG analysis • Capillary gas determination • Transcutaneous monitoring • Oxygenation indices

48. Clinical monitoring Ventilator Parameters • PIP • PEEP • MAP • RR • Ti & I:E Ratio • FiO2 • VT • Trends of Ventilator Parameters • Pulmonary Graphics

49. Hemodynamic Stability • Oxygenation • Adequacy of Circulation

50. Radiological Monitoring When to do CXR ? • At the start of ventilation • After ET tube change • Sudden deterioration • Prior to extubation • Post extubation