Ventilator graphics

1. Mechanical Ventilation Graphics Dr.s.vijay anand

2. Purposes of monitoring graphics Allow users to interpret, evaluate, and troubleshoot the ventilator and the patient’s response to the ventilator. Monitor the patient’s disease status (C and Raw). Assess the patient’s response to therapy. Monitor proper ventilator function Allow fine tuning of ventilator to decrease WOB, optimize ventilation, and maximize patient comfort

3. Mechanical Ventilation Graphics SCALARS LOOPS

4. SCALARS Flow/Time Pressure/Time Volume/Time

5. Types of Waveforms • Scalars : Plot pressure, volume, or flow against time. Time is the x-axis. •

6. Pressure-Volume Flow-Volume LOOPS

7. Loops: Plot pressure or flow against volume. (P/V or F/V). There is no time component

8. Basic shapes of waveforms •Generally, the ramp waves are considered the same as exponential shapes, so you really only need to remember three: square, ramp, and sinewaves .

9. 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

10. Pressure Waveform In Volume modes, the shape of the pressure wave will be a ramp for mandatory breaths •In Volume modes, adding an inspiratory pause (or hold) will add a small plateau to the waveform. •This is thought to improve distribution of ventilation

11. Pressure Waveform 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.

12. Distinguishing breath type Trigger Sensitivity Plateau pressure Rate & I:E Peak Flow [VC] PS characteristics Lung mechanics Application of a P/T curve

13. Y axis – Pressure X axis – Time A-B = Inspiration B – C = Expiration MAP = Area under curve PIP = Max insp Pressure PEEP = baseline Pressure Pressure / Time Curves - Overview

14. Press wave is square [constant] P wave is not affected by lung mechanics or pt flow demand Flow rate is according to lung mechanics, set P, & Insp effort by pt Flow wave rises rapidly to meet set P, then decreases to a point necessary to maintain set P. [ expo decay or continuously variable decelerating pattern] Note the P & V plateaus in regard to the Flow which ends before Ti is over This condition provides the greatest volume possible for that set P Indicates the lung has met equilibrium [Plateau] Pressure / Time Curves - Overview PC

15. PC

16. This condix has a much shorter Ti [not allowing for Plateau] but for a longer Te Delivered volume is slightly decreased Pressure / Time Curves -Overview

17. A-B Inspiration B-C Expiration D shows second breath beginning before 1 st breath has exhaled fully Indicates needing to decrease rate, increase Te, or decrease Ti Pressure / Time Curves - Applica tion Adequate Rate, I:E

18. Pressure / Time Curves - Applica tion Breath type Mechanical breath [volume] Note at point A – there is no negative deflex Consistent Ti & Volume delivery Pressure continues to rise until set V is reached, then breath cycles VC

19. Pressure / Time Curves - Applica tion Breath type Mechanical Breath [ Pressure] Consistent Ti & Pressure delivery P reaches limit early in I and holds for Ti No Trigger PC

20. Pressure / Time Curves - Applica tion Breath type Triggered Mechanical Volume Breath Note at point A – there is a negative deflection, indicating the pt initiated a triggered breath VC

21. Identified by negative inflex triggering breath varying Inspiratory times Note the different times of the above curves VC-SIMV w/ PS Pressure / Time Curves - Applica tion Breath type Pressure Support breaths PS V C

22. A – represents Inspirax of a spontaneous Breath B – represents Expirax of a Spontaneous breath Spontaneous Mode – Every breath is pt triggered & spontaneous in nature Pressure / Time Curves – Applica tion Breath type Spontaneous breath

23. s

24. A – scooped out waveform b/c inadequate flow for pt demand B – bulging indicates too much flow Pressure / Time Curves - Applica tion Adjusting Peak Flow [ VC]

25.   Note the Exp Volume is not = insp Vol Indicating a leak Flow & Press both return to zero Volume / Time Curves - Applic Air Trapping v. Air Leaks

26.   Note the Exp Volume > Insp Volume Indicating active Ex due to air trapping Note the flow & Press never return to zero Volume / Time Curves - Applic Active Exhalation

27. Y axis = flow X axis = Time A-B = inspiration Above x axis B-C = Expirax Below X axis D- Peak Inspiratory Flow E = Peak Expiratory Flow [ PEFR] Flow / Time Curves - Overview

28. B-D = Ti B-C = INSP FLOW C-D = INSP PAUSE D-F = Te D-E = EXP FLOW E-F = EXP FLOW has ended Rate could be increased until insp begins at point E on this pt without air trapping Flow / Time Curves - Overview

29. 1 2 3 4 5 6 SEC 120 -120 V . LPM Expiratory Flow Rate and Changes in Expiratory Resistance

30. Exp flow is low & slow, taking a long time to rid the lungs of volume. Te is barely adequate to allow for lung emptying before next breath This pt may have COPD or severe asthma Bronchodilator response may be helpful to evaluate Evaluation of Raw

31. A – Insp flow does return to zero Adequate Ti B – Insp flow does NOT return to zero Inadequate Ti Allows for increasing Ti this will increase Vt without increasing Pressure Evaluation of Ti [ PC]

32. Pressure remains constant at level set Flow increases as pt demand increases in order to maintain the set Pressure level Volume increases Active Inhalation during PC

33. Loops Pressure-Volume Loops Flow-Volume Loops

34. Pressure-Volume Loop 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O V T

35. Mandatory Breath Inspiration 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O V T

36. Mandatory Breath Expiration 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O Inspiration V T Counterclockwise

37. Spontaneous Breath Inspiration 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O V T Clockwise

38. Spontaneous Breath Inspiration Expiration 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O V T Clockwise

39. Assisted Breath 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O Assisted Breath V T

40. Assisted Breath Inspiration 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O Assisted Breath V T

41. Assisted Breath Inspiration Expiration 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 P aw cmH 2 O Assisted Breath V T Clockwise to Counterclockwise

42.   Dashed line plotted based on the Static Compliance calculation drawn from zero to peak PA Peak PA – Pstatic or Pplat Note that the point at which Peak PA is also the point where the volume plateaus P TA = xairway pressure [difference b/w the airway opening(Pawo) and the Alveoli (PA)] Static Compliance Line

43. Triangle AP A E Represents the amount of mechanical work to overcome the compliance [elastic forces] of the chest Area ACBP A represents amount of work to overcome Raw during Insp Triangle AP A D represents amount of work to overcome Raw during Exp The insp area [area w/in the hysteresis] represents total WOB due to Raw

44. P TA = xairway pressure [difference b/w the airway opening( Pawo ) and the Alveoli (PA)] Represents the amount of pressure needed to overcome resistance of the lung If Raw increases this distance will increase If flow [turbulence] increases, so does this distance

45. Triangle ABE Total WOB Elastance & Resistance More on WOB

46. Slope = line drawn from zero through the Pplat As slope increases [ Pplat decreases] compliance increases for a set volume As slope decreases [ Pplat increase] compliance decreases for a set volume Assessing Compliance

47. Decreased compliance dz’s Fibrosis, ARDS, pna , Pulm edema, Atelectasis , etc. Short Time constant states(fast lung units) Increased compliance dz’s Emphysema, uncomplicated COPD, etc. Long Time constant states(slow lung units) Pressure remains constant while volumes differ Assessing Compliance - PC

48. Volume remains Constant Pressures change Assessing Compliance - VC

49. Overdistension B A 20 40 60 -20 -40 -60 0.2 0.4 0.6 LITERS P aw cmH 2 O C A = inspiratory pressure B = upper inflection point C = lower inflection point V T

50. X axis – Volume Y axis – Flow Insp – above x axis Exp – below x axis Opposite of a PFT tracing Peak Exp Flow Rate Peak insp flow Flow / Volume Loop – Overview

51. •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

52. Flow / Volume Loop - Application •Air trapping •Airway Obstruction •Airway Resistance •Bronchodilator Response • Insp /Exp Flow •Flow Starvation •Leaks •Water or Secretion accumulation •Asynchrony

53. Flow -Volume Loops Volume Control Flow Volume Tidal Volume Inspiration Expiration

54. Flow -Volume Loops Volume Control Flow Volume Peak Expiratory Flow Peak Inspiratory Flow Tidal Volume Inspiration Expiration

55. A – normal Raw & exp flow B – increased Raw & reduced exp flow C – markedly increased Raw & reduced exp flow Insp flow is unaffected by Raw b/c the vent is delivering a constant flow [square waveform] Assessing Raw

56. Inner loop – increased airway resistance Outer Loop – after BD therapy Spike an artifact that reflects the release of gas trapped in the patient circuit during inspiration compressible volume release It should not be valued as PEFR Assessing Bronchodilator therapy

57. Note the severe scooping of the exp waveform Assessing Obstruction

58. Exp volume does not return to zero Circuit or pt leak Assessing Leaks

59. Exp flow does not return to zero Pt still exhaling volume when next breath begins Air Trapping

60. Bronchodilator Response 2 1 1 2 3 3 V LPS . BEFORE V LPS .

61. Bronchodilator Response 2 1 1 2 3 3 V LPS . BEFORE AFTER Worse 2 1 1 2 3 3 V LPS .

62. Bronchodilator Response 2 1 1 2 3 3 V LPS . V T INSP EXH BEFORE AFTER Worse Better 2 1 1 2 3 3 V LPS . 2 1 1 2 3 3 V LPS .

63. Remember! Waveforms and loops are graphical representation of the data generated by the ventilator. Typical Tracings Pressure-time, Flow-time, Volume -time Loops Pressure-Volume Flow-Volume Assessment of pressure, flow and volume waveforms is a critical tool in the management of the mechanically ventilated patient.

64. Reference Susan philbeam textbook of mechanical ventilation