Post on 09-Jun-2015
transcript
A System for Analyzing Ventilator Waveforms
Start with the airway pressure screen
Step 1….determine the CPAP level
This is the baseline position from which there is a downward deflection on, at least, beginning of inspiration, and to which the airway pressure returns at the end of expiration.
Step 2…. is the patient triggering?
There will be a negative deflection into the CPAP line just before inspiration.
Step 3: what is the shape of the pressure wave? .
If the curve has a flat top, then the breath is pressure limited, if it has a triangular or shark’s fin top, then it is a volume breath
Look at the flow screen:
Step 3…what is the flow pattern? –
If it is constant flow (square shaped) this must be volume controlled, If decelerating, it can be any mode.
Step 3 cont….Is the patient gas trapping? –
Expiratory flow does not return to baseline before inspiration commences (i.e. gas is trapped in the airways at end-expiration).
Step 4: the patient is triggering – is this a pressure supported or SIMV breath?
This is easy, the pressure supported breath looks completely differently than the volume control or synchronized breath: the PS breath has a decelerating flow pattern, and has a flat topped airway pressure wave. The synchronized breath has a triangular shaped pressure wave.
Flow terminated
Step 5: patient is triggering, is this pressure support or pressure control?
The fundamental difference between PS and PC is the length of the breath – In PC, the vent determine the inspired time and all breaths have an equal “i” time. In PS, the pt determined the duration of inspiration, which varies from breath to breath and flow termination seen as per setting.
Step 6.. is the patient synchronizing with the ventilator?
Each time the ventilator is triggered a breath should be delivered. If the number of triggering episodes is greater than the number of breaths, the patient is asynchronous with the ventilator. Further, if the peak flow rate of the ventilator is inadequate, then the inspiratory flow will be "scooped" inwards, and the patient appears to be fighting the ventilator.
SPONTANEOUS BREATH.....................
Time (sec)
P
V
F
SOME BASIC CONCEPTS…..
Effects of Changes in Ventilator settings on Waveforms……………1. How RR changes Cycle time thereby iTime and eTime
2. How Flow Rate changes iTime and eTime
A post-operative pt brought to PICU And placed on VENT……With following settings……
• Tidal volume………… 750 ml..(0.75 L)
• Resp rate ……………. 15 / min
• Insp flow rate ……….. 30 L / min
• Airways resistance …. 10 cm H2O/L//sec
• Compliance …………… 0.05 L/cm H2O (50 ml/cm H2O)
• Mode ……………………. CMV
0 1 2 3 4 5 6 7 8 9 10 11 12
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0 1 2 3 4 5 6 7 8 9 10 11 12
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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
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Modes of ventilation…..Graphical Display
CMV …….(VOLUME VENTILATION)CMV …….(VOLUME VENTILATION)
Preset VT
Volume Cycling
Dependent onCL & Raw
Time (sec)
Flow(L/m)
Press(cm H2O)
Vol(mL)
Preset Peak Flow
Time triggered, Flow limited, Volume cycled Ventilation
ASSISTED MODE…………(VOLUME CONTROL VENTILATION)ASSISTED MODE…………(VOLUME CONTROL VENTILATION)
Time (sec)
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Preset VT
Volume Cycling
Patient triggered, Flow limited, Volume cycled Ventilation
SIMV……(VOLUME CONTROL VENTILATION)SIMV……(VOLUME CONTROL VENTILATION)
Spontaneous Breaths
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
SIMV+PS….(VOLUME CONTROL VENTILATION)SIMV+PS….(VOLUME CONTROL VENTILATION)
Flow
Pressure
Volume
(L/min)
(cm H2O)
(ml)
Set PS level
PS Breath
Flow-cycled
SIMV+PS + CPAPVOLUME CONTROL VENTILATIONSIMV+PS + CPAPVOLUME CONTROL VENTILATION
F
P
V
Set PS level
CPAP level
CONTROLLED MODE (PRESSURE VENTILATION)CONTROLLED MODE (PRESSURE VENTILATION)
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Time (sec)
Time-Cycled
Set PC level
Time Triggered, Pressure Limited, Time Cycled Ventilation
ASSISTED MODE …..(PRESSURE VENTILATION)ASSISTED MODE …..(PRESSURE VENTILATION)
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Set PC level
Time (sec)
Time-Cycled
Patient Triggered, Pressure Limited, Time Cycled Ventilation
P
F
V
Set PC level
Time
SIMV Mode….Pressure control Ventilation
Spontaneous Breath
P
F
V
SIMV + PS ……..Pressure control Ventilation
PS Breath
Set PS levelSet PC level
Time
Time-CycledFlow-Cycled
P
F
V
Set PC level
Time
SIMV + PS + CPAP…….Pressure control Ventilation
Set PS level
CPAP level
Triggering ? ??
PSV
Time (sec)
F
P
V
Flow Cycling
Set PS levelSet PS level
Patient Triggered, Pressure limited, Insp Flow Cycled
CPAP
Time
CPAP level
F
P
V
CPAP + PSV
Set PS level
CPAP level
Time
F
P
V
Flow Cycling
THANKS