VENTILATOR GRAPHICS,Purposes of monitoring graphics

VENTILATOR GRAPHICS,Purposes of monitoring graphics

1. VENTILATOR GRAPHICS 1

2. Purposes of monitoring graphics Allow users to interpret, evaluate, and troubleshoot the ventilator and the patient’s response to the ventilator. Allow fine tuning of ventilator to decrease WOB, optimize ventilation, and maximize patient comfort. 2

3. Scalars and Loops: Scalars : Plot pressure, volume, or flow against time. Time is the x-axis. Loops : Plot pressure or flow against volume. (P/V or F/V). There is no time component 3

4. Types of Waveforms Basic shapes of waveforms: Square wave: Represents a constant or set parameter. For example, pressure setting in PC mode or flowrate setting in VC mode. Ramp wave: Represents a variable parameter Will vary with changes in lung characteristics Can be accelerating or decelerating Sine wave: Seen with spontaneous, unsupported breathing Basic shapes of waveforms 4

5. Types of Waveforms Pressure Modes Volume Modes 5

6. Pressure Waveform In Volume modes, the shape of the pressure wave will be a ramp for mandatory breaths . In Pressure modes, the shape of the pressure wave will be a square shape. This means that pressure is constant during inspiration or pressure is a set parameter. Can be used to assess : PIP , Pplat Asynchrony Triggering Effort 6

7. Pressure Waveform The area under the entire curve represents the mean airway pressure (MAP). 7

8. Pressure Waveform The baseline for the pressure waveform will be higher, when PEEP is added. There will be a negative deflection just before the waveform with patient triggered breaths. 8

9. Pressure Waveform While performing an expiratory hold maneuver , trapped air will cause the waveform to rise above the baseline. An acceptable amount of auto-PEEP should be < 5cm H2O 9

10. Volume Waveform The Volume waveform will generally have a “mountain peak” appearance at the top. It may also have a plateau, or “flattened” area at the peak of the waveform. There will also be a plateau if an inspiratory pause time is set or inspiratory hold maneuver is applied to the breath 10

11. Volume Waveform Can be used to assess : Air trapping (auto-PEEP) Leaks Tidal Volume Active Exhalation Asynchrony 11

12. Volume Waveform 12

13. Volume Waveform If the exhalation side of the waveform doesn’t return to baseline, it could be from air-trapping or there could be a leak (ET tube, vent circuit, chest tube, etc.) 13

14. Flow Waveform In Volume modes, the shape of the flow wave will be square. This means that flow remains constant or flowrate is a set parameter . In Pressure modes, the shape of the flow waveform will have ramp pattern. Some ventilators allow you to select the desired flow pattern in Volume Control mode. 14

15. Flow Waveform Can be used to assess: Air trapping (auto-PEEP) Airway Obstruction Bronchodilator Response Active Exhalation Breath Type (Pressure vs. Volume) Inspiratory Flow Asynchrony Triggering Effort 15

16. Flow Waveform 16

17. Flow Waveform The decelerating flow pattern may be preferred over the constant flow pattern. The same tidal volume can be delivered, but with a lower peak pressure 17

18. Flow Waveform If the expiratory portion of the waveform doesn’t return to baseline before the start of the next breath starts, there could be air trapping. (emphysema, improper I:E ratio) 18

19. Flow Waveform To assess response to bronchodilator therapy, you should see an increase in peak expiratory flow rate. The expiratory portion of the curve should return to baseline sooner. 19

20. Pressure/Volume Loops Volume is plotted on the y-axis, Pressure on the x-axis . Inspiratory curve is upward, Expiratory curve is downward. Spontaneous breaths go clockwise and positive pressure breaths go counter clockwise . The bottom of the loop will be at the set PEEP level. It will be at 0 if there’s no PEEP set. If an imaginary line is drawn down the middle of the loop, the area to the right represents inspiratory resistance and the area to the left represents expiratory resistance. 20

21. Pressure/Volume Loops Can be used to assess: Lung Over distention Airway Obstruction Bronchodilator Response Respiratory Mechanics (C/Raw) WOB Flow Starvation Leaks Triggering Effort The top part of the P/V loop represents Dynamic compliance (Cdyn). Cdyn = Δvolume / Δpressure 21

22. Pressure/Volume Loops Overdistention Pressure continues to increase with little or no change in volume, creating a “bird beak”. Fix by reducing amount of tidal volume delivered 22

23. Pressure/Volume Loops As airway resistance increases, the loop will become wider. An increase in expiratory resistance is more commonly seen. Airway Resistance 23

24. Pressure/Volume Loops The expiratory portion of the loop doesn’t return to baseline. This indicates a leak A Leak 24

25. Flow/Volume Loops Flow is plotted on the y axis and volume on the x axis Flow volume loops used for ventilator graphics are the same as ones used for Pulmonary Function Testing, (usually upside down). Inspiration is above the horizontal line and expiration is below. The shape of the inspiratory portion of the curve will match the flow waveform. The shape of the exp flow curve represents passive exhalation . Can be used to determine the PIF, PEF, and Vt Looks circular with spontaneous breaths 25

26. Flow/Volume Loops Can be used to assess: Air trapping Airway Obstruction Airway Resistance Bronchodilator Response Insp/ Exp Flow Flow Starvation Leaks Water or Secretion accumulation Asynchrony 26

27. Flow/Volume Loops • If there is a leak, the loop will not meet at the starting point where inhalation starts and exhalation ends. It can also occur with air-trapping. 27

28. Flow/Volume Loops Airway Obstruction The F-V loop appears “upside down” on most ventilators . 28

29. Rise Time The inspiratory rise time determines the amount of time it takes to reach the desired airway pressure or peak flow rate. Used to assess if ventilator is meeting patient’s demand in Pressure Support mode. I n SIMV, rise time becomes a % of the breath cycle. 29

30. Rise Time If rise time is too fast, you can get an overshoot in the pressure wave, creating a pressure “spike”. If this occurs, you need to increase the rise time. This makes the flow valve open a bit more slowly. If rise time is too slow, the pressure wave becomes rounded or slanted, when it should be more square. This will decrease Vt delivery and may not meet the patient’s inspiratory demands. If this occurs, you will need to decrease the rise time to open the valve faster. 30

31. Inspiratory Cycle Off The inspiratory cycle off determines when the ventilator flow cycles from inspiration to expiration, in Pressure Support mode. Also know as– I nspiratory flow termination, Expiratory flow sensitivity, Inspiratory flow cycle %, E-cycle , etc… The flow-cycling variable is given different names depending on the brand of ventilator. 31

32. Inspiratory Cycle Off The breath ends when inspiratory flow has dropped to a specific flow value. 32

33. Inspiratory Cycle Off In the above example, the machine is set to cycle inspiration off at 30% of the patient’s peak inspiratory flow. 33

34. Inspiratory Cycle Off A –The cycle off percentage is too high, cycling off too soon. This makes the breath too small. (not enough Vt.) 60% 10% B – The cycle off percentage is too low, making the breath too long. This forces the patient to actively exhale (increase WOB), creating an exhalation “spike”. 34

35. Ventilator asynchrony 35

36. Ventilator asynchrony TRIGGER Ineffective Double Reverse Auto CYCLE Premature Delayed FLOW Insufficient flow Excess flow 36

37. TYPES OF TRIGGER ASYNCHRONY Ineffective efforts Double Reverse Auto 37

38. Ineffective Efforts 38

39. INEFFECTIVE TRIGGERING PATIENT FACTORS Determining factor Therapeutic strategy High sedation Reduce or discontinue neural drive depressants, sedation or NMBA Respiratory muscle weakness Optimize electrolytes Nutrition Dynamic hyperinflation (auto – PEEP) Decrease PS levels (PSV mode) Increase expiratory time Bronchodilator & increase external PEEP 39

40. Double triggering 40

41. Double triggering VENTILATOR FACTOR Determining factor Therapeutic strategy Inspiratory time short relative to neural inspiratory time Increase inspiratory time Low level of assist (low tidal volume in VCV) Modes that allow variation in tidal volume, such as PCV Relatively high threshold for cycling off Decrease the cycling threshold percentage (PSV) Patient factor Correct underlying fever, anxiety 41

42. Reverse triggering 42

43. Reverse triggering Occurs mainly in patients who are deeply sedated . No single effective treatment strategy . Reducing RR to increase patient triggered breaths . Reducing sedation and awakening the patient Switching to support modes Neuromuscular Paralysis 43

44. Auto triggering 44

45. Auto triggering Determining factor Therapeutic strategy Ventilator : Excessive sensitivity System leak Condensate in the ventilator circuit Optimize the sensitivity setting Increase trigger threshold Correct leak Inflate ETT cuff Remove condensate Aspirate secretions Reduce secretion 45

46. Auto triggering Patient factors : Transmission of pressure or flow oscillations because of cardiac activity. Optimize the sensitivity setting 46

47. TYPES OF FLOW ASYNCHRONY Insufficient flow Excess flow 47

48. Insufficient flow 48

49. Insufficient flow Determining factor Therapeutic strategy Ventilator : In VCV, the flow setting is too low In PCV and PSV  the applied pressure is too low, long rise time In VCV, increase inspiratory flow or switch to PCV or PSV 49

50. Insufficient flow Patient factors : Excessive ventilator demand, increased neural drive Reduce neural drive and metabolic demand. control fever, pain, metabolic acidosis and anxiety. 50

51. Excess flow 51

52. Excess flow Determining factor Therapeutic strategy In VCV, the flow setting is too high In VCV, decrease inspiratory flow In PCV and PSV, the applied pressure is too high, rise time is too short (overshoot) In PCV and PSV, decrease applied pressure, increase rise time 52

53. TYPES OF CYCLE ASYNCHRONY Premature cycling Delayed cycling 53

54. Premature cycling 54

55. Premature cycling Determining factor Therapeutic strategy Ventilator : Inspiratory time is too short relative to patient inspiratory time Low level of assist Relatively high threshold for cycling off In VCV, decrease inspiratory flow or increase tidal volume or add end inspiratory pause In PCV, increase inspiratory time. Lower threshold for cycling or higher PS in PSV. 55

56. Premature cycling Patient factors : Restrictive respiratory mechanisms in PSV, as in pulmonary fibrosis Intense inspiratory muscle activity In PSV, decrease/lower the cycling threshold 56

57. Delayed cycling 57

58. Delayed cycling Determining factor Therapeutic strategy Inspiratory time > patent inspiratory time In VCV, high Vt , low flow and pause In PSV low flow threshold for cycling off, high support In VCV, respiratory flow. In PCV, inspiratory time. In PSV, cycling threshold % or PS . Bronchodilator, steroid therapy, aspiration of secretions. 58

59. THANK YOU 59