Basic modes of mechanical ventilation

understand evolution and principles of Basic modes of mechanical ventilation in children

1. Mechanical Ventilation Basic Modes Lokesh Tiwari AIIMS Patna CME on Mechanical Ventilation: Bench to Bedside AIIMS RAIPUR: 22 nd August 2015

2. What are ventilators ? A machine that generates a controlled flow of gas into a patient’s airways Supportive role to buy time

3. Mechanical ventilation Several models have evolved over time- Negative pressure ventilation Positive pressure ventilation Simple pneumatic system New generation microprocessor controlled systems. The basic function and applications remain common.

4. Basic Ventilator Parameters Tidal volume Frequency PIP Plateau Pressure PEEP Inspiratory Time Expiratory time I:E Ratio

5. Basic Ventilator Parameters Mode Tidal volume Frequency PIP Plateau Pressure PEEP Inspiratory Time Expiratory time I:E Ratio

6. Starting a ventilator: Mode Mode denotes interplay b/w patient and the ventilator Describes the style of breath support based on relationship between the various possible types of breath and inspiratory – phase variables

7. Where to Start ? CPAP, IPAP, EPAP , NIV Pressure control, V olume control CMV, Assist Control, IMV, SIMV, PSV, ASV , MMV, APRV PCV, PRVC , PSV, VCIRV , Volume Support, Auto Mode, BiLevel , BiPAP , HFJV, HFOV

8. Objective From

9. Objective To

10. Objectives Understand how ventilators control breath delivery, phase and control variables. Understand the basic modes of ventilation. Combinations, tailor-making, mix and match…

11. The ventilator circuit

12. The ventilator circuit 50 psi air 50 psi O2 Blender Air-O2 mixture of desired FiO2 at 50 psi Stepped down pressure Flow regulator Pressure regulating valve T-piece & ETT tube Insp limb Exp limb

13. Flow regulators / PEEP Flow in ventilator circuit- constant Flow in ET & patient airway- keeps changing in magnitude & direction !! T-connection ETT Baby’s airway PEEP PIP Flow sensor

14. What does flow sensor do? Flow in ventilator circuit- constant T-connection ETT Flow sensor Insp flow  RR = tidal vol Exp flow - insp flow = peri-tube leak

15. Ventilatory P hases Inspiration : Inspiratory valve opens and expiratory valve is closed Inspiratory pause : inspiratory valve and expiratory valve closed Expiration : Inspiratory valve closed and expiratory valve open Expiratory pause : Inspiratory valve and expiratory (or PEEP ) valve closed at end of expiration Ti Te

16. Phase Variables: Trigger , Limit and Cycling

17. Phase variables Trigger : ventilator (time)- triggered or patient (pressure or flow) triggered Limit : flow-limited or pressure-limited Cycling : volume, time, flow or pressure cycled .

18. Phase variables: Trigger What causes the breath to begin (signal to open the inspiratory valve) Machine (controlled): the ventilator will trigger regular breaths at a frequency which will depend on the set respiratory rate, ie , they will be ventilator time triggered . Patient (assisted): If the patient does make an effort to breathe and the ventilator can sense it (by either sensing a negative inspiratory pressure or an inspiratory flow ) and deliver a breath, it will be called a patient-triggered breath.

19. Phase Variables: Trigger

20. Phase Variables: Trigger

21. Phase variables: Limit Factor which controls the inspiration inflow Flow Limited: a fixed flow rate and pattern is set and maintained throughout inspiration. An adequate tidal volume ( Ti dependent) Pressure will be variable (comp and resistance dependent) Pressure limited: the pressure is not allowed to go above a preset limit. The tidal volume will be variable (comp and resistance dependent)

22. Phase variables: Cycling Signal that stops the inspiration and starts the expiration . Without inspiratory pause: one signal With inspiratory pause: two cycling signals (one to close inspiratory valve and the second to open the expiratory valve) Volume Time Flow Pressure : back-up form of cycling when the airway pressure reaches the set high-pressure alarm level

23. The ventilatory cycle Ti Te PIP PEEP 0.35 sec 0.65 sec 1 resp cycle= Ti + Te

24. Mechanical Time (sec) Spontaneous P aw (cm H 2 O) Inspiration Expiration Expiration Inspiration Breath type: Spontaneous vs Mechanical vs assisted Assisted

25. Control variables Pressure: Pressure signal is the feedback signal (Pressure Preset) Volume: Volume signal is the feedback signal. usually measure the flow and turn it into volume signal electronically. (volume preset) Time Flow Combinations

26. Volume Control Ventilation Pressure Volume Flow Preset Peak Flow Preset V t Dependent on C l & R aw Time (sec)

27. Pressure Control Ventilation Flow Pressure Volume C l C l Set PC level Time (sec)

28. Basic Modes of Ventilation Controlled M echanical Ventilation Assist Control Ventilation Intermittent Mandatory Ventilation Synchronized Intermittent Mandatory Ventilation Pressure Support Combinations

29. Controlled mandatory ventilation (CMV) The ventilator delivers Preset tidal volume (or pressure) at a time triggered (preset) respiratory rate. As the ventilator controls both tidal volume (pressure) and respiratory rate, the ventilator “controls” the patients minute volume. Pressure

30. Controlled mandatory ventilation (CMV) Volume controlled Pressure controlled

31. Preset V T Volume Cycling Dependent on C L & R aw Time (sec) Flow (L/m) Pressure (cm H 2 O) Volume (mL) Preset Peak Flow Time triggered, Flow limited, Volume cycled Ventilation Controlled mandatory ventilation (Volume-Targeted)

32. Pressure Flow Volume (L/min) (cm H 2 O) (ml) Time (sec) Time- Cycled Set PC level Time Triggered, Pressure Limited, Time Cycled Ventilation Controlled mandatory ventilation (Pressure-Targeted)

33. Controlled mandatory ventilation (CMV) Patient can not breath spontaneously Patient can not change the ventilator respiratory rate Suitable only when patient has no breathing efforts Disease or Under heavy sedation and muscle relaxants

34. Controlled mandatory ventilation (CMV) Asynchrony and increased work of breathing. Not suitable for patient who is awake or has own respiratory efforts Can not be used during weaning

35. Assist Control Ventilation

36. Time (sec) Control ventilation (CMV) Assist / control ventilation Pressure Control Control Assisted Assist Control Ventilation

37. Control ventilation (CMV) Assist / control ventilation Pressure Assist Control Ventilation A set tidal volume (volume control) or a set pressure and time (pressure control) is delivered at a minimum rate Additional ventilator breaths are given if triggered by the patient Mandatory breaths: Ventilator delivers preset volume and preset flow rate at a set back-up rate Spontaneous breaths: Additional cycles can be triggered by the patient but otherwise are identical to the mandatory breath.

38. Assist Control Ventilation Tidal volume (V T ) of each delivered breath is the same, whether it is assisted breath or controlled breath Minimum breath rate is guaranteed (controlled breaths with set V T ) Control ventilation (CMV) Assist / control ventilation Pressure

39. Assist Control Ventilation (volume ) Assist Control Ventilation (Pressure) Assist Control Ventilation

40. Time (sec) Patient / T imeTriggered , Pressure Limited, Time Cycled Ventilation Pressure Flow Volume Set PC level Time-Cycled Pt triggered Time triggered Assist Control Ventilation (Pressure)

41. Patient / Time triggered, Flow limited, Volume cycled Ventilation Assist Control Ventilation (Volume) Time (sec) Flow Pressure Volume Preset V T Volume Cycling

42. Assist Control Ventilation Asynchrony taken care of to some extent Low work of breathing, as every breath is supported and tidal volume is guaranteed. Hyperventilation Respiratory alkalosis. Natural breaths are not allowed Breath stacking High volumes and pressures Control ventilation (CMV) Assist / control ventilation Pressure

43. Assist Control Ventilation Hyperventilation and breath stacking can usually be overcome by choosing optimal ventilator settings and appropriate sedation. Control ventilation (CMV) Assist / control ventilation Pressure

44. Intermittent Mandatory Ventilation (IMV) Pressure Machine breaths are delivered at a set rate (volume or pressure limit) Time (sec)

45. Intermittent Mandatory Ventilation (IMV) Pressure Machine breaths are delivered at a set rate (volume or pressure limit) Patient is allowed to breath spontaneously from either a demand valve or a continuous flow of gases but not offering any inspiratory assistance. Time (sec)

46. Intermittent Mandatory Ventilation (IMV) Pressure Patient’s capability determines Tidal volume of spontaneously breaths Some freedom to breath naturally even on mechanical ventilator Time (sec)

47. Intermittent Mandatory Ventilation (IMV) Pressure Random chance of breath stacking and asynchrony: Increased WOB Uncomfortable feeling Time (sec)

48. Intermittent Mandatory Ventilation (IMV) Pressure controlled IMV Volume controlled IMV

49. Intermittent Mandatory Ventilation (IMV) Pros: Freedom for natural spontaneous breaths even on machine Lesser chances of hyperventilation Cons: Asynchrony Random chance of breath stacking. Increase work of breathing Random high airway pressure (barotrauma) and lung volume ( volutrauma ) Setting appropriate pressure limit is important to reduce the risk of barotrauma

50. Can we synchronize it?

51. Synchronized Intermittent Mandatory Ventilation Ventilator delivers either patient triggered assisted breaths or time triggered mandatory breath in a synchronized fashion so as to avoid breath stacking If the patient breathes between mandatory breaths, the ventilator will allow the patient to breathe a normal breath by opening the demand (inspiratory) valve but not offering any inspiratory assistance.

52. Synchronization window Pressure Time interval just prior to time triggering in which the ventilator is responsive to the patient’s inspiratory effort. Time (sec) Time trigerring

53. SIMV Pressure Patient trigerred synchronized breath If the patient makes a spontaneous inspiratory effort that falls in sync window, the ventilator is patient triggered to deliver an assisted breath and will count it as mandatory breath Time trigerred mandatory breath

54. SIMV Pressure Patient trigerred synchronized breath if patient does not make an inspiratory effort then ventilator will deliver a time triggered mandatory breath. Time trigerred mandatory breath

55. SIMV Pressure Patient trigerred synchronized breath if patient does not make an inspiratory effort then ventilator will deliver a time triggered mandatory breath. Time trigerred mandatory breath If the pt triggers outside this window , vent will allow this spontaneous breath to occur by opening the demand (inspiratory) valve but does not offer any inspiratory assistance.

56. Synchronized Intermittent Mandatory Ventilation Pressure 3 types of breathing: Patient initiated assisted ventilation, Ventilator generated controlled ventilation , Unassisted spontaneous breath.

57. Synchronized Intermittent Mandatory Ventilation P-SIMV V-SIMV

58. Synchronized Intermittent Mandatory Ventilation (SIMV) It allows patients to assume a portion of their ventilatory drive: Weaning is possible Greater work of breathing than AC ventilation and therefore some may not consider it as the initial ventilator mode Friendly cardiopulmonary interaction: Negative inspiratory pressure generated by spontaneous breathing leads to increased venous return, which theoretically may help cardiac output and function

59. Pressure Support Ventilation Pressure (or Pressure above PEEP) is the setting variable No mandatory breaths Applicable on Spontaneous breaths: a preset pressure assist, Flow cycling: terminates when flow drops to a specified fraction (typically 25%) of its maximum. Patient effort determines size of breath and flow rate.

60. Pressure Support Ventilation Pressure (or Pressure above PEEP) is the setting variable No mandatory breaths Applicable on Spontaneous breaths: a preset pressure assist, Flow cycling: terminates when flow drops to a specified fraction (typically 25%) of its maximum. Patient effort determines size of breath and flow rate

61. Pressure Support Ventilation Pressure (or Pressure above PEEP) is the setting variable No mandatory breaths Applicable on Spontaneous breaths: a preset pressure assist, Flow cycling: terminates when flow drops to a specified fraction (typically 25%) of its maximum. Patient effort determines size of breath and flow rate.

62. Pressure Support Ventilation It augments spontaneous V T decreases spontaneous rates and WOB Used in conjunction with spontaneous breaths in any mode of ventilation. No guarantee of tidal volume with changing respiratory mechanics, No back up ventilation in the event of apnea.

63. Pressure Support Ventilation Provides pressure support to overcome the increased work of breathing imposed by the disease process, the endotracheal tube, the inspiratory valves and other mechanical aspects of ventilatory support Allows for titration of patient effort during weaning. Helpful in assessing extubation readiness

64. SIMV + PS Ventilation Pressure Spontaneous breath with PS

65. Summary

66. Time (sec) Control ventilation (CMV) Assist / control ventilation Pressure Control Control Assisted Pressure Pressure

67. Thank you!! You have done it!!!