BASICS OF WAVEFORM INTERPRETATION Michael Haines, MPH, RRT-NPS, AE-C

1. BASICS OF WAVEFORM INTERPRETATIONMichael Haines, MPH, RRT-NPS, AE-C

2. Objectives • Identify graphic display options provided by mechanical ventilators. • Describe how to use graphics to • more appropriately adjust the patient ventilator interface.

3. Monitoring and analysis of graphic display of curves and loops during mechanical ventilation has become a useful and popular way to determine not only how patient are being ventilated but also a way to assess problems occurring during ventilation.

4. Uses of Flow, Volume, and Pressure Graphic Display • Confirm mode functions • Detect auto-PEEP • Determine P-V synchrony • Assess and adjust trigger levels • Measure the work of breathing • Adjust tidal volume and minimize overdistension • Assess the effect of bronchodilator administration • Detect equipment malfunctions • Determine appropriate PEEP level

5. Uses of Flow, Volume, and Pressure Graphic Display • Evaluate adequacy of inspiratory time in pressure control ventilation • Detect the presence and rate of continuous leaks • Assess inspiratory termination criteria during Pressure Support Ventilation • Determine appropriate Rise Time

6. The graphic display of flow, pressure and volume is generally visualized in two formats: Waveforms Loops

7. Pressure vs. Time Flow vs. Time Volume vs. Time Most Commonly used Waveforms

8. 30 A B C PIP Baseline Paw Mean Airway Pressure cmH2O Sec 1 2 3 4 5 6 -10 Pressure vs. TimeCurve

9. Pressure-Time Curve 20 Volume Ventilation Pressure Ventilation Paw Expiration cmH2O Sec 1 2 3 4 5 6

10. PIP:complianceresistancevolumeflow PEEP Pressure PEEP time

11. No active breathing Treats lung as single unit PIP resistance flow Pplat end-inspiratory alveolar pressure compliance tidal volume PEEP

12. Work to Trigger 30 Paw cmH2O Sec 1 2 3 4 5 6 -10

13. Adequate Flow During Volume-Control Ventilation 30 Adequate flow P aw Time (s) cmH2O 1 2 3 -10

14. Flow set too low Inadequate Flow During Volume-Control Ventilation 30 Adequate flow P aw Time (s) cmH2O 1 2 3 -10

15. Patient/Ventilator SynchronyVolume Ventilator Delivering a Preset Flow and Volume Adequate Flow Paw Sec cmH2O 1 2 3 4 5 6 -20

16. Patient/Ventilator SynchronyThe Patient Outbreathing the Set Flow Air Starvation Paw Sec cmH2O 1 2 3 4 5 6 -20

17. Plateau Time 30 Inadequate plateau time Paw SEC cmH2O 1 2 3 4 5 6 -20

18. Plateau Time 30 Adequate Plateau Time Paw SEC cmH2O 1 2 3 4 5 6 -20

19. Flow vs.Time Curve 120 INSP Inspiration . V SEC LPM 1 2 3 4 5 6 EXH 120

20. Flow vs.Time Curve 120 INSP Inspiration . V SEC LPM 1 2 3 4 5 6 Expiration EXH 120

21. Flow vs.Time Curve Constant Flow Descending Ramp 120 INSP Inspiration . V SEC LPM 1 2 3 4 5 6 EXH 120

22. Flow-Time Curve 120 INSP . Insp. Pause V SEC LPM 1 2 3 4 5 6 Expiration EXH 120

23. Inspiratory TimeShort Normal Long

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

25. 120 . SEC V LPM 1 3 4 5 6 2 120

26. Obstructed Lung Delayed flow return

27. Combined Screens 20 Volume Ventilation Paw cmH2O Sec 1 2 3 4 5 6 . V

28. Pressure-Time and Flow-Time Curves 20 Volume Ventilation Paw • Expiration cmH2O Sec 1 2 3 4 5 6 . V

29. Pressure-Time and Flow-Time CurvesDifferent Inspiratory Flow Patterns 20 Volume Ventilation Paw • Expiration Inspiration cmH2O Sec 1 2 3 4 5 6 . V

30. Pressure-Time and Flow-Time Curves 20 Pressure Ventilation Volume Ventilation Inspiratory Time Paw cmH2O Sec 1 2 3 4 5 6 . V

31. Rise TimeInspiratoty Rise Time PercentageFlow Acceleration Percentage • How quickly inspiratory flow accelerates to achieve set pressure.

32. Flow Acceleration Percent Rise Time Minimal Pressure Overshoot P Slow rise Moderate rise Fast rise . V Pressure Relief Time

33. Patient / Ventilator SynchronyVolume Ventilation Delivering a Preset Flow and Volume 30 Adequate Flow Paw Sec cmH2O 1 2 3 4 5 6 -20

34. Patient / Ventilator SynchronyThe Patient Is Outbreathing the Set Flow 30 Air Starvation Paw Sec cmH2O 1 2 3 4 5 6 -20 What options do we have?

35. We Can Switch to a Decelerating Flow Pattern: More Flow Up Front 120 . V SEC LPM 1 2 3 4 5 6 -120

36. If Peak Flow Remains the Same, I-Time Increases: Could Cause Asynchrony 120 . V SEC LPM 1 2 3 4 5 6 -120

37. Changing Flow Waveform in Volume Ventilation: Effect on Inspiratory Time 120 . V SEC LPM 1 2 3 4 5 6 -120

38. Increased Peak Flow: Decreased Inspiratory Time 120 . V SEC LPM 1 2 3 4 5 6 -120

39. Detecting Auto-PEEP 120 . V SEC LPM 1 2 3 4 5 6 Zero flow at end exhalation indicates equilibration of lung and circuit pressure -120 Note: There can still be pressure in the lung behind airways that are completely obstructed

40. Detecting Auto-PEEP 120 . V SEC LPM 1 2 3 4 5 6 The transition from expiratory to inspiratory occurs without the expiratory flow returning to zero 120

41. Flow Waveform flow inhalation time 0 auto-PEEP exhalation

42. PEEP 7 cm H2O sensitivity -1 cm H2O sensitivity -1 cm H2O auto-PEEP 3 cm H2O auto-PEEP 10 cm H2O PEEP 10 cm H2O PEEP 10 cm H2O trigger effort = 4 cm H2O trigger effort = 11 cm H2O Auto-PEEP should be measured with set PEEP = 0

43. 800 ml Inspiration VT SEC 1 2 3 4 5 6 Volume vs.Time Curve

44. Volume vs.Time Curve 800 ml • Expiration VT SEC 1 2 3 4 5 6

45. Typical Volume Curve I-Time E-Time 1.2 A B VT Liters SEC 1 2 3 4 5 6 -0.4 A = inspiratory volume B = expiratory volume

46. Air Trapping or Leaks 1.2 A VT Liters SEC 1 2 3 4 5 6 -0.4 A = exhalation that does not return to zero

47. Loops • Pressure-Volume Loops • Flow-Volume Loops

48. VT LITERS 0.6 0.4 0.2 Paw cmH2O -60 40 20 0 20 40 60 Pressure-Volume Loop

49. VT LITERS 0.6 0.4 Inspiration 0.2 Paw cmH2O -60 40 20 0 20 40 60 Mandatory Breath

50. Mandatory Breath VT Counterclockwise LITERS 0.6 • Expiration 0.4 Inspiration 0.2 Paw cmH2O -60 40 20 0 20 40 60