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BASICS OF WAVEFORM INTERPRETATION Michael Haines, MPH, RRT-NPS, AE-C. Objectives. Identify graphic display options provided by mechanical ventilators. Describe how to use graphics to more appropriately adjust the patient ventilator interface. - PowerPoint PPT Presentation
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BASICS OF WAVEFORM INTERPRETATION
Michael Haines, MPH, RRT-NPS, AE-C
Objectives
• Identify graphic display options provided by mechanical ventilators.
• Describe how to use graphics to more appropriately adjust the patient
ventilator interface.
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.
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
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
The graphic display of flow, pressure and volume is generally visualized in two
formats:
WaveformsLoops
Most Commonly used Waveforms
• Pressure vs. Time
• Flow vs. Time
• Volume vs. Time
Pressure vs. Time Curve
1 2 3 4 5 6
30
SecPawcmH2O
A BC
PIP
Baseline
Mean Airway Pressure
-10
Pressure-Time Curve
1 2 3 4 5 6
20
Sec
PawcmH2O
Pressure Ventilation
Expiration
Volume Ventilation
Pre
ssur
e
time
PIP:complianceresistancevolumeflowPEEP
PEEP
PEEP
PIP
Pplat
resistanceflow
compliancetidal volume
No active breathingTreats lung as single unit
end-inspiratoryalveolar pressure
Work to Trigger
1 2 3 4 5 6
30
Sec
PawcmH2O
-10
Adequate Flow During Volume-Control Ventilation
30
Time (s)
-10
1 2
awPcmH2O
Adequate flow
3
Inadequate Flow During Volume-Control Ventilation
30
Time (s)
-10
1 2
awPcmH2O
Adequate flow
Flow set too low3
Patient/Ventilator SynchronyVolume Ventilator Delivering a Preset Flow and Volume
Adequate Flow
1 2 3 4 5 6
-20
SecPawcmH2O
Patient/Ventilator SynchronyThe Patient Outbreathing the Set Flow
Air Starvation
1 2 3 4 5 6
-20
SecPawcmH2O
Plateau Time
Inadequate plateau time
-20
1 2 3 4 5 6
30
SECPawcmH2O
Adequate Plateau Time
-20
1 2 3 4 5 6
30
SECPawcmH2O
Plateau Time
Flow vs.Time Curve
1 2 3 4 5 6SEC
120
120EXH
INSP
V.
LPM
Inspiration
Flow vs.Time Curve
1 2 3 4 5 6SEC
120
120EXH
INSP
V.
LPM
Inspiration
Expiration
Flow vs.Time Curve
1 2 3 4 5 6SEC
120
120EXH
INSP
Inspiration
V.
LPM
Constant Flow Descending Ramp
Flow-Time Curve
1 2 3 4 5 6SEC
120
120EXH
INSP
Insp. Pause
Expiration
V.
LPM
Inspiratory TimeShort Normal Long
1 2 3 4 5 6
SEC
120
-120
V.
LPM
Expiratory Flow Rate and Changes in Expiratory Resistance
1 2 3 4 5 6
SEC
120
120
V.
LPM
Obstructed Lung
Delayed flow return
Combined Screens
1 2 3 4 5 6
20
Sec
PawcmH2O
V.
Volume Ventilation
Pressure-Time and Flow-Time Curves
1 2 3 4 5 6
20
Sec
PawcmH2O
Expiration
V.
Volume Ventilation
Pressure-Time and Flow-Time CurvesDifferent Inspiratory Flow Patterns
1 2 3 4 5 6
20
Sec
PawcmH2O
Expiration
V.
Volume Ventilation
Inspiration
20
Pressure-Time and Flow-Time Curves
1 2 3 4 5 6Sec
PawcmH2O
V.
Pressure Ventilation
Inspiratory Time
Volume Ventilation
Rise TimeInspiratoty Rise Time Percentage
Flow Acceleration Percentage
How quickly inspiratory flow accelerates to achieve set pressure.
Time
Minimal Pressure Overshoot
Pressure Relief
Slow rise Moderate rise Fast rise
P
V.
Flow Acceleration Percent Rise Time
Patient / Ventilator SynchronyVolume Ventilation Delivering a Preset Flow and Volume
Adequate Flow
1 2 3 4 5 6
30
-20
SecPawcmH2O
What options do we have?
Air Starvation
1 2 3 4 5 6
30
-20
SecPawcmH2O
Patient / Ventilator SynchronyThe Patient Is Outbreathing the Set Flow
We Can Switch to a Decelerating Flow Pattern: More Flow Up Front
1 2 3 4 5 6
SEC
120
-120
V.
LPM
If Peak Flow Remains the Same, I-Time Increases: Could Cause Asynchrony
LPM1 2 3 4 5 6
SEC
120
-120
V.
Changing Flow Waveform in Volume Ventilation: Effect on Inspiratory Time
1 2 3 4 5 6
SEC
120
-120
V.
LPM
Increased Peak Flow: Decreased Inspiratory Time
1 2 3 4 5 6
SEC
120
-120
V.
LPM
Note: There can still be pressure in the lung behind airways that are completely obstructed
Detecting Auto-PEEP
LPM
Zero flow at end exhalation indicates equilibration of lung and circuit pressure
1 2 3 4 5 6
SEC
120
-120
V.
Detecting Auto-PEEP
The transition from expiratory to inspiratory occurs without the expiratory flow returning to zero
1 2 3 4 5 6
SEC
120
120
V.
LPM
time
flow
inhalation
exhalation
0auto-PEEP
Flow Waveform
sensitivity-1 cm H2O
auto-PEEP10 cm H2O
trigger effort = 11 cm H2O
sensitivity-1 cm H2O
auto-PEEP3 cm H2O
trigger effort = 4 cm H2O
PEEP7 cm H2O
PEEP10 cm H2O
PEEP10 cm H2O
Auto-PEEP should be measured with set PEEP = 0
Volume vs.Time Curve
Inspiration
SEC
800 ml
2 3 4 5 61
VT
Volume vs.Time Curve
Expiration
SEC
800 ml
2 3 4 5 61
VT
Typical Volume Curve
1 2 3 4 5 6
SEC
1.2
-0.4
VT
Liters
I-TimeE-Time
A B
A = inspiratory volume
B = expiratory volume
Air Trapping or Leaks
1 2 3 4 5 6
SEC
1.2
-0.4
VT
Liters
A
A = exhalation that does not return to zero
Loops
• Pressure-Volume Loops
• Flow-Volume Loops
Pressure-Volume Loop
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
VT
Mandatory Breath
Inspiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
VT
Mandatory Breath
Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
Inspiration
VT Counterclockwise
Spontaneous Breath
Inspiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
VTClockwise
Spontaneous Breath
InspirationExpiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
VTClockwise
Work of Breathing
0 20 40 60-20-40-60
0.2
0.4
0.6
LITERS
PawcmH2O
VT
Assisted Breath
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
Assisted Breath
VT
Assisted Breath
Inspiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
Assisted Breath
VT
Assisted Breath
Inspiration
Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
PawcmH2O
Assisted Breath
VT Clockwise to Counterclockwise
Pressure-Volume Loop Changes
0 20 40 60-20-40-60
0.2
0.4
0.6
LITERS
PawcmH2O
VT
Changes in Compliances
Indicates a drop in compliance (higher pressure for the same volume)
0 20 40 602040-60
0.2
0.4
0.6
LITERS
PawcmH2O
VT
Lung Overdistension
Overdistension
B
A
0 20 40 60-20-40-60
0.2
0.4
0.6
LITERS
PawcmH2O
C
A = inspiratory pressure
B = upper inflection point
C = lower inflection point
VT
Pressure – Volume Loops
Pressure – Volume Loops
Pressure – Volume Loops
Flow -Volume Loops Volume Control
Flow
Volume
Tidal Volume
Inspiration
Expiration
Flow -Volume Loops Volume Control
Flow
Volume
Peak Expiratory FlowPeak Inspiratory FlowTidal Volume
Inspiration
Expiration
ETT or Circuit Leaks
Obstructive Pattern
Bronchodilator Response
2
1
1
2
3
3
VLPS
.
BEFORE
VLPS
.
Bronchodilator Response
2
1
1
2
3
3
VLPS
.
BEFORE AFTERWorse
2
1
1
2
3
3
VLPS
.
Bronchodilator Response
2
1
1
2
3
3
VLPS
.VT
INSP
EXH
BEFORE AFTERWorse Better
2
1
1
2
3
3
VLPS
.
2
1
1
2
3
3
VLPS
.
What Mode is This?
What Mode is This?
What Mode is This?
What Mode is This?
Remember Waveforms and loops are graphical representation of the data collected 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 key aspect in the management of the mechanically ventilated patient.
The End!
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