Sri Ramajeyam Om Anandamayi Chaithanyamayi Sathyamayi Parame! Dr. S. Ahanatha Pillai, M.D.,D.A., Emeritus Professor Dr.

1. Sri Ramajeyam Om Anandamayi Chaithanyamayi Sathyamayi Parame! Dr. S. Ahanatha Pillai,M.D.,D.A., Emeritus Professor Dr. M. G. R. Medical University Former Professor of Anaesthesiology Madurai Medical College & Govt. Rajaji Hospital Madurai

2. DEPARTMENT OF ANAESTHESIOLOGY Madurai Medical College Madurai

3. Basics of VentilatorTherapy

4. Ventilation – Movement of Air Respiratory Physiology Movement of air in & out oflungs Purpose • Transfer O2into Blood • Removal CO2from Blood • Maintaining Normal Blood Gas

5. Respiratory Failure Inability of the system to maintainNormal • Blood GasLevels • Acid – BaseStatus Respiratory Failure -Ventilatory Failure

6. RespirationExternalInternal(Tissue) Ventilation Utilisation of O2 Mechanics Moving air Cell Metabolismin& out of lung Al-Cap Mem Diffusion Release of CO2 PerfusionO2into Blood CO2 into Alveoli Ventilation -----Perfusion----- Diffusion

7. Disorders of Breathing • Airways • Lungs • Thoracic Cage & Muscles (Apparatus) • Brain (Central Control)

8. Ventilator Therapy Useful only in Reversible Depression or Damage • Brain (Central Control) • Mechanics of Breathing(Apparatus) • Lungs Pulmonary Oedema, ARDS– Helpful Chronic - Irreversible Damage - ?

9. Respiratory Mechanics “The mechanical changes that happen in Respiratory apparatus which cause movement of air in and out of lungs” Respiratory Apparatus • Thoracic Cage • Respiratory Muscles • Lungs within Thoracic Cage

10. Mechanical Ventilation Common Indications • Failure of Respiratory Mechanics Neurological – G.B.S or N.M.Block • DepressionofRespiratory Center ByOpioids, Head Injury etc

11. Mechanical Ventilation A Machine performs the Work of Breathing instead of Inspiratory Muscles Expiration is always passive process

12. Ventilator • “A devicewhichcauses bulk movementof gases in andout of lungsand takes over orassists the functionof Respiratorymuscles”

13. “The user should know what the Ventilator can do, not how it does that” - J. S. Robinson

14. Any Ventilator Has two basic components Brain • A Control Mechanism to command what & how to do Muscle • A Driving Mechanism to carry out the command

15. Simplest Ventilator • Divides the MinuteVolume into Number of Breaths (Tidal Volume) Example – Ambu’sBag • The Brain • The Muscle Belongs to operator

16. Simplest Ventilator

17. Types • Negative Pressure Ventilators • PositivePressure Ventilators Negative Pressure Ventilator • Createsextra thoracicNegative pressure intermittently • Mimics normalrespiration eg: TankVentilators&Cuirass

18. Principle of Negative Pressure Ventilator Tank Ventilator Cabinet Ventilator or Iron Lung Cuirass Ventilator

19. Emerson Tank Ventilator

20. Iron lung ward Ranchos Los Amigos Hospital 1953

21. Emerson Iron Lung UsedbyBarton Hebert1950 – 2003 - Louisiana Museum – Center for Disease control & Prevention

22. Modern Transparent Tank Ventilator The Tank has clear acrylic lid & a gasket around neck The ventilator machine is seen as a Box

23. Cuirass Ventilator This patient has Hypoventilation during sleep

24. Patient Supported by Cuirass

25. Positive Pressure Ventilator All modern Ventilators The Principle is I.P.P.V • Positive Pressure (Supra-atmospheric) applied to proximal airway forces air into Lungs – Inspiration • Expiration is allowed passively • This is repeated - Intermittently

26. Spontaneous Respiration Inspiration Expiration

27. Positive Pressure Respiration - IPPV Inspiration Expiration

28. + _ + 2 cm – 2 cm + _ + 15 cm 0 (Atm) I:E ratio 1:2

29. IndicationsforVentilation • Apnoea orImpendingApnoea • Hypoventilation • Fatigue orParalysisof Respiratory muscles (Myesthenia, Polyneuritis) • Persistent Tachypnoea • Paradoxical Respiration • FlailChest

30. Advantages of Ventilation • Takes overWork of Breathing • Improves Gas Exchange • Opens upcollapsed alveoli (Recruiting) • Permits HeavySedation & Analgesia ignoring Respiratory Depression • May reversePulmonary Oedema

31. Problems “ A common problem in patients supported by Mechanical ventilation is that they are hyperventilated, which leads to Respiratoryalkalosis”

32. Respiratory Alkalosis • Hypocapnoea(Hypocarbia) • O2 Dissociation Curve – Shift toLeft • Cerebral Vasoconstriction • I.C.T. – Reduced, Cerebral Oedema • “Inverse Steal” in Brain pathology • Hypotension • Respiratory Centre – Depressed

33. Effects on CVS • Thoracic Neg. Pump –Abolished • VenousReturn–Reduced • Cardiac Output – Reduced • Pulm. BloodFlow – Reduced • Pulm. Cap.Pressure – Raised • Strain on RightVentricle

34. Patient -Ventilator Asynchrony Ventilator – Muscle Overload “With improperventilator settings, patient fights the ventilator” Results in need for • More Sedation or Muscle Relaxant • Undue delay in weaning process

35. Atrophy of Diaphragm • Ventilation for> 40 hoursresults in reduction of Diaphragmmuscle mass • Minimal amountof WOB prevents reduction of Diaphragmaticstrength and maintains endurance • Assist / ControlMode Prevents Respiratorymuscle atrophy

36. Oxygen Toxicity & Stretch Injury Two possible injuries • Excess O2 (High F i O2) O2 Free radicalmediated lung injury • Excess Flow Over distention – Stretch injury Barotrauma – in Poor compliance Volutrauma – in Good compliance

37. InadequateTidal Volume Leaks &ExpansibleVolume • Leaks in the circuitsmay cause lossofgas that will not reach the lungs • When positivepressure is applied, tubesof breathing circuitmayexpand and accommodatesome volume ofgases that willnot be delivered to the lungs

38. ExhaledTidal Volume is the actual tidal volume the lungs received That is measured by • Wright’s Respirometer • Volumeter Bellows(ExpSpirometer) • Transducers- Digital Display

39. The panel must have Two Displays • What we set on the Machine • What actually the patient receives

40. Methods of Artificial Ventilation • Self inflating resuscitator bag- Ambu • Simple mechanical device- EastRadcliff • Sophisticated ventilators “As long as the lungsare well ventilated, by some method,life can be saved ” 1952 Denmark polio epidemic had proved it

41. East Radcliff Ventilator (Positive – Negative pressure Respiratory pump) Still it isbetter than aBag, Mask &Hands

42. Modern Ventilators Brain - Control Mechanism • Microprocessor Modules Muscle - Driving Power • Pneumatic – Air or O2 • Electricity • Combined

43. Ventilator Breath (Mechanical Breath) EachCycleis divided intoFour Phases • InspiratoryPhase • Changeover -Inspiration to Expiration (Cycling) • ExpiratoryPhase • Changeover - Expiration toInspiration

44. Basic Mechanical Breath 2 (Cycling) 1 3 + 0 4 _ Initiation of Inspiration Any change can be done only on this

45. 2 2 Special Modes Changeover from Insp – Expi(Cycling) * Volume * Pressure * Time * Flow * IMV * SIMV * MMV * CPAP * BIPAP * APRV 1 3 Inspi Phase Pressure Expi Phase • * PSV • * PCV • * PAV • * IRV * NEEP * ZEEP * PEEP + 0 Time ChangeovertoInspiration 4 – * Time (CMV) * Patient Triggered (Assist) * Patient Triggered / Time (A/C) All the possible modifications in a Mechanical Breath

46. Inspiratory Phase • Pressure Support PSV • Pressure Control PCV • Proportional Assist PAV • Inverse Ratio IRV

47. Change over from Inspiration to Expiration • Volume Cycling – Preset Volume • Pressure Cycling – Preset Pressure • Time Cycling – Preset Time(Pr or Vol) • Flow Cycling – Preset Flow Microprocessorscan doall thesein one

48. Expiratory Phase • NEEPNegative End Expiratory X • ZEEPExpiratory Retard X • PEEP Positive EndExpiratory Pressure • CPAP Continuous Positive Airway PEEP applied Spontaneous Breathing

49. IPPV & NEEP NEEP Negative End Expiratory Pressure _

50. Expiratory Retard - Interrupted line is normal expiration ZEEP Zero End Expiratory Pressure