BASICS OF WAVEFORM INTERPRETATION

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BASICS OF WAVEFORM INTERPRETATION

• RET 2284
• Principles of Mechanical Ventilation

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(No Transcript)
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Objectives

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

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Introduction

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

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Uses of Flow, Volume, and Pressure Graphic Display

• Confirm mode functions
• Detect auto-PEEP
• Determine patient-ventilator 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

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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

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Measured Parameters

• Flow
• Pressure
• Volume
• Time

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Most Commonly Used Waveforms (Scalars)

• Pressure vs. Time
• Flow vs. Time
• Volume vs. Time

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Pressure vs. Time Curve
10
Pressure-Time Curve
20
Pressure Ventilation
Volume Ventilation
Paw
cmH2O
Sec
1
2
3
4
5
6
11
Patient Triggering
30
Paw
cmH2O
Sec
1
2
3
4
5
6
-10
12
Adequate Flow During Volume-Control Ventilation
30
Adequate flow
P
aw
Time (s)
cmH2O
1
2
3
-10
13
Inadequate Flow During Volume-Control Ventilation
30
Adequate flow
P
aw
Time (s)
cmH2O
1
2
3
-10
14
Patient/Ventilator SynchronyVolume Ventilator
Delivering a Preset Flow and Volume
Adequate Flow
Paw
Sec
cmH2O
1
2
3
4
5
6
-20
15
Patient/Ventilator SynchronyThe Patient
Outbreathing the Set Flow
Air Starvation
Paw
Sec
cmH2O
1
2
3
4
5
6
-20
16
Plateau Time
30
Inadequate plateau time
Paw
SEC
cmH2O
1
2
3
4
5
6
-20
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Plateau Time
30
Adequate Plateau Time
Paw
SEC
cmH2O
1
2
3
4
5
6
-20
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Flow vs.Time Curve
120
INSP
Inspiration
.
V
SEC
LPM
1
2
3
4
5
6
EXH
120
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Flow vs.Time Curve
120
INSP
Inspiration
.
V
SEC
LPM
1
2
3
4
5
6
Expiration
EXH
120
20
Flow vs.Time Curve
Constant Flow
Descending Ramp
120
INSP
Inspiration
.
V
SEC
LPM
1
2
3
4
5
6
EXH
120
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Flow-Time Curve
120
INSP
.
Insp. Pause
V
SEC
LPM
1
2
3
4
5
6
Expiration
EXH
120
22
Inspiratory Time Short Normal
Long
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Expiratory Flow Rate and Changes in Expiratory
Resistance
120
.
SEC
V
LPM
1
2
3
4
5
6
-120
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A Higher Expiratory Flow Rate and a Decreased
Expiratory Time Denote a Lower Expiratory
Resistance
120
.
SEC
V
LPM
1
3
4
5
6
2
120
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Obstructed Lung
Delayed flow return
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Pressure-Time and Flow-Time Curves
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Volume Ventilation
Paw
Expiration
cmH2O
Sec
1
2
3
4
5
6
.
V
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Pressure-Time and Flow-Time CurvesDifferent
Inspiratory Flow Patterns
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Volume Ventilation
Paw
Expiration
Inspiration
cmH2O
Sec
1
2
3
4
5
6
.
V
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Pressure-Time and Flow-Time Curves
20
Pressure Ventilation
Volume Ventilation
Inspiratory Time
Paw
cmH2O
Sec
1
2
3
4
5
6
.
V
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Rise Time

• How quickly set pressure is reached

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Flow Acceleration Percent Rise Time
Minimal Pressure Overshoot
P
Slow rise Moderate rise
Fast rise
.
V
Pressure Relief
Time
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Patient / Ventilator SynchronyVolume Ventilation
Delivering a Preset Flow and Volume
30
Adequate Flow
Paw
Sec
cmH2O
1
2
3
4
5
6
-20
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Patient -Ventilator SynchronyThe Patient Is
Outbreathing the Set Flow
30
Air Starvation
Paw
Sec
cmH2O
1
2
3
4
5
6
-20
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If Peak Flow Remains the Same, I-Time Increases
Could Cause Asynchrony
120
.
V
SEC
LPM
1
2
3
4
5
6
-120
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Changing Flow Waveform in Volume Ventilation
Effect on Inspiratory Time
120
.
V
SEC
LPM
1
2
3
4
5
6
-120
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Increased Peak Flow Decreased Inspiratory Time
120
.
V
SEC
LPM
1
2
3
4
5
6
-120
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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
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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
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Volume vs.Time Curve
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Volume vs.Time Curve
800 ml
Expiration
VT
SEC
2
3
4
5
6
1
40
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
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Leaks
1.2
A
VT Liters
SEC
1
2
3
4
5
6
-0.4
A exhalation that does not return to zero
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Setting Appropriate I-Time
600 cc
450 cc
SEC
0
1
2
3
4
5
6
120
SEC
1
2
3
4
5
6
120
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Setting Appropriate I-Time
600 cc
450 cc
500 cc
SEC
0
1
2
3
4
5
6
120
Lost VT
SEC
1
2
3
4
5
6
120
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Loops

• Pressure-Volume Loops
• Flow-Volume Loops

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Pressure-Volume Loop

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Mandatory Breath

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

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Spontaneous Breath
VT
Clockwise
LITERS
0.6
0.4
Inspiration
0.2
Paw
cmH2O
0
20
40
60
20
40
-60
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Spontaneous Breath
VT
Clockwise
LITERS
0.6
0.4
Inspiration
Expiration
0.2
Paw
cmH2O
0
20
40
60
20
40
-60
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Work of Breathing
VT
LITERS
0.6
0.4
0.2
Paw
60
40
20
-20
-60
0
-40
cmH2O
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Assisted Breath
VT

LITERS
0.6
0.4
Assisted Breath
0.2
Paw
cmH2O
0
20
40
60
20
40
-60
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Assisted Breath
VT

LITERS
0.6
0.4
Assisted Breath
0.2
Inspiration
Paw
cmH2O
0
20
40
60
20
40
-60
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Assisted Breath
VT
Clockwise to Counterclockwise
LITERS
0.6
Expiration
0.4
Assisted Breath
0.2
Inspiration
Paw
cmH2O
0
20
40
60
20
40
-60
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Pressure-Volume Loop Changes
VT
LITERS
0.6
0.4
0.2
Paw
60
40
20
-20
-60
0
-40
cmH2O
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Changes in Compliances
Indicates a drop in compliance (higher pressure
for the same volume)
VT
LITERS
0.6
0.4
0.2
Paw
60
40
20
20
-60
0
40
cmH2O
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Overdistension
VT
A inspiratory pressure B upper inflection
point C lower inflection point
LITERS
0.6
A
0.4
B
0.2
C
Paw
60
40
20
-20
-60
0
-40
cmH2O
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Lung Overdistension
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Normal Flow-Volume Loops
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Flow -Volume Loops Volume Control
Tidal Volume
Flow
Inspiration
Volume
Expiration
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Flow -Volume Loops Volume Control
Tidal Volume
Peak Inspiratory Flow
Peak Expiratory Flow
Flow
Inspiration
Volume
Expiration
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ETT or Circuit Leaks
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Obstructive Pattern
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Bronchodilator Response
BEFORE
3
2
1
.
.
V LPS
V LPS
1
2
3
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Bronchodilator Response
BEFORE
AFTER
Worse
3
3
2
2
1
1
.
.
V LPS
V LPS
1
1
2
2
3
3
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Bronchodilator Response
BEFORE
AFTER
Better
Worse
3
3
INSP
2
2
1
1
.
.
V LPS
V LPS
VT
1
1
2
2
3
3
EXH
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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.