Ventilator Graphics

VENTILATOR GRAPHICS

Purpose

• Graphics are waveforms that reflect the patient-ventilator system and their interaction

• Purpose of monitoring graphics includes– Monitors the patients disease status (C and Raw)– Calculates respiratory mechanics– Assesses patient response to therapy– Monitors ventilator function– Allows fine tuning of ventilator to decrease WOB and

optimize ventilation– Allows user to interpret, evaluate, and troubleshoot

ventilator and patients’ response to ventilator

Types of waveforms

• Scalars: plot pressure/volume/flow against time…time is the x axis

• Loops: plot pressure/volume/flow against each other…there is no time component

• Six basic waveforms:– Rectangular: AKA swuare wave– Descending ramp: AKA decelerating ramp– Ascending ramp: AKA accelerating ramp– Sinusoidal: AKA sine wave– Exponential rising– Exponential decaying

Types of waveforms seen

• Pressure waveforms– Rectangular – Exponential rise– Sine

• Volume waveforms– Ascending ramp– Sinusoidal

• Flow waveforms– Rectangular– Sinusoidal– Ascending ramp– Descending ramp– Exponential decay

Flow PatternsFlow Patterns

ACCELERATINGACCELERATING

DECELERATINGDECELERATING

SINESINE

SQUARESQUARE

Flow PatternsFlow Patterns

ACCELERATINGACCELERATING

DECELERATINGDECELERATING

SINESINE

SQUARESQUARE

http://co-5.college-online.com/../../Power%20Point%20Presentations/Flow%20vs%20Time%20Folder/Flow%20Patterns.ppt

Pressure-Time Scalar

• Machine-triggered breaths have no negative deflection at the start• Patient triggered breaths may have a negative deflection at the start

if the breath is being pressure triggered…the greater the patient effort to trigger the breath, the greater the negative deflection seen…no deflection see with flow triggering

• In volume modes, the shape will be exponential rise for mandatory breaths and sinusoidal for spontaneous breaths…if PS is added to spontaneous breaths, then the waveform will be square on the spontaneous breaths

• In pressure modes, the shape will be rectangular for mandatory breaths and sinusoidal for spontaneous breaths…if PS added to the spontaneous breaths, they will be rectangular also

• If PEEP is added, the baseline during expiration will be above zero• The area under the entire curve equals the Paw (mean airway

pressure)

Components of Inflation Pressure


Begin InspirationBegin Inspiration Begin ExpirationBegin Expiration

11

22

BBAA

1. PIP 1. PIP 2. 2. PPplatplat/Alveolar Pressure/Alveolar PressureA. Airway ResistanceA. Airway ResistanceB. Distending PressureB. Distending Pressure

Time (sec)Time (sec)

PPawaw

(cm H(cm H22O)O)



Begin InspirationBegin Inspiration Begin ExpirationBegin Expiration

11

22

BBAA

1. PIP 1. PIP 2. 2. PPplatplat/Alveolar Pressure/Alveolar PressureA. Airway ResistanceA. Airway ResistanceB. Distending PressureB. Distending Pressure


PPawaw

(cm H(cm H22O)O)

http://co-5.college-online.com/../../Power%20Point%20Presentations/Pressure%20vs%20Time%20Folder/Components%20Inflation.ppt

Use of Pressure-Time Scalars

Patient Ventilator Pt-Vent Interaction

Air trapping (auto-PEEP)

Breath type Asynchrony

Airway obstruction

PIP and plateau Triggering effort

Active exhalation PEEP/CPAP

Bronchodilator response

Pressure waveform change

Resp mechanics (C/Raw)

It/Et/I:E

Volume-Time Scalar

• Ascending ramp shape if a square wave flow pattern is used…sinusoidal if the sine wave flow pattern is used…exponential rise if the decelerating flow pattern is used

• Plateaus at the peak of the curve in PC/PS• If the exhalation side of the curve doesn’t

return to baseline, it could be auto-PEEP or there could be a leak (eg-around ETT or through a chest tube)

Volume vs Time ScalarVolume vs Time Scalar

InspirationInspiration

ExpirationExpiration


Volume Volume (ml)(ml)

Inspiratory Tidal VolumeInspiratory Tidal Volume

TTII

Volume vs Time ScalarVolume vs Time Scalar




Volume Volume (ml)(ml)

Inspiratory Tidal VolumeInspiratory Tidal Volume

TTII

http://co-5.college-online.com/../../Power%20Point%20Presentations/Volume%20vs%20Time/Volume%20vs%20Time.ppt

Use of Volume-Time Scalars


Air trapping (auto-PEEP)

Breath types Asynchrony

Active exhalation

Volume waveform shape

Vt

Leaks

Flow-Time Scalars

• No evidence supports one flow pattern over another…the square wave might distribute gas more evenly in patients with a unilateral lung dx…decelerating ramp may distribute gas more evenly because the high burst of flow at the beginning would pop alveoli open and allow for gas exchange during the entire breath

• If expiratory flow doesn’t return to baseline before the next breath starts, there’s auto-PEEP present (air trapping is occurring)

• Volume control on some vents allows you to select the flow pattern you want

• All pressure breaths (PC, PS, PRVC, VS) will have a decelerating ramp flow pattern

• CPAP has a sinusoidal flow pattern unless PS has been added

Use of Flow-Time Scalars


Air trapping Breath types Asynchrony

Airway obst Flow waveform shape

Triggering effort

Active exhalation Inspiratory flow

Bronchodilator response

Flow starvation (vol vent)

Resp mechanics (C/Raw)

Adjustment of It (Press vent)

Adjustment of rise time

Pressure-Volume Loops

• Volume is plotted on the y axis and pressure on the x axis (can also be plotted the other way around)

• Inspiratory curve is upward and expiratory curve is downward

• Spontaneous breaths go clockwise and positive pressure breaths go counterclockwise

• The bottom of the loop will be at the set PEEP level or be at 0 if there’s no PEEP set

• I starts and E ends at the bottom of the loop…I ends and E starts at the top of the loop

• The loop is almost square in PC/PS because of pressure limiting during I

Essentials of Ventilator Graphics ©2000 RespiMedu

Pressure-Volume LoopPressure-Volume Loop

Volume Volume ((mLmL))

Insp

iratio

n

Insp

iratio

n

Expi

ration

Expi

ration

PIPPIP

VVTT

PPawaw (cm H(cm H22O)O)


Pressure-Volume LoopPressure-Volume Loop

Volume Volume ((mLmL))

Insp

iratio

n

Insp

iratio

n

Expi

ration

Expi

ration

PIPPIP

VVTT


http://co-5.college-online.com/../../Power%20Point%20Presentations/Pressure%20Volume%20Loop%20Folder/Pressure-Volume%20Loop%20Components.ppt

Abnormal PV Loops• If an imaginary line is drawn down the middle of the loop,

the area to the right represents inspiratory resistance/WOB and the area to the left represents expiratory resistance/WOB (just the opposite for spont breaths- I is to the left and E is to the right)

• The more vertical the loop lays, the lower the lung C, the more horizontal it lays, the higher the lung C

• The fatter the loop, the higher the airway resistance…you can tell if it’s I or E resistance by looking at whether the right or left side bulges out more

• A bird beak at the top of the loop represents over-distension

• A pig tail at the bottom indicates patient triggering…the bigger the pig tail, the higher the patient WOB to trigger the breath

• The loop won’t meet at the bottom with airtrapping or leaks

Use of PV Loops

Patient•Airway obst•Active exhalation•Bronchodilator response•Lung overdistension•Resp mechanics•WOB

Ventilator •Adjusting PS levels•Flow starvation•Leaks

Pt-Vent Interaction•Triggering effort

Flow-Volume Loops

• Flow is plotted on the y axis and volume on the x axis• Inspiration is above the horizontal line and expiration is

below (some vents reverse this and I is below while E is above)

• The shape of the insp flow curve will match what’s set on the ventilator

• The shape of the exp flow curve represents passive exhalation…it’s long and more drawn out in patients with less recoil

• Can be used to determine the PIF, PEF, and Vt• Looks circular with spontaneous breaths• Looks squared but set at an angle with PC/PS breaths


Flow-Volume LoopFlow-Volume Loop

Volume (ml)Volume (ml)

1

2

34



Flow Flow (L/ min)(L/ min)

FRC


Flow-Volume LoopFlow-Volume Loop

Volume (ml)Volume (ml)

1

2

34



Flow Flow (L/ min)(L/ min)

FRC

http://co-5.college-online.com/../../Power%20Point%20Presentations/Flow%20Volume%20Loop%20Folder/Flow%20Volume%20Loop%20Components.ppt

Abnormal FV Loops

• The expiratory curve “scoops” with high expiratory resistance

• If the patient is air trapping or has a leak, the loop will not meet at the left side where I starts/E ends

• If water/secretions are building up in the airway or circuit, the loop becomes very jagged

Use of FV Loops

Patient•Air trapping•Airway obst•Airway resistance•Active exhalation•Bronchodilator response

Ventilator•Insp flow•Exp flow•Flow starvation•Vt•Leaks•Water or secretion build-up

Pt-Vent Interaction•asynchrony

Air Trapping (auto-PEEP)• Causes:

– increased exp resistance (either in the airways or in the circuit)– Insufficient expiratory time– Early collapse of unstable alveoli/airways during exhalation

• How to ID it on the graphics– Pressure time: while performing an expiratory hold, the waveform rises

above baseline– Flow-time: the exp flow doesn’t return to baseline before the next

breath begins– Volume-time: the exp portion doesn’t return to baseline– FV Loop: the loop doesn’t meet at the baseline– PV Loop: the loop doesn’t meet at the baseline

• How to Fix:– ID the cause and resolve– Give a treatment, suction, change the HME, decrease It/increase flow,

add PEEP

Air TrappingAir Trapping



NormalNormalPatientPatient


Air TrappingAir TrappingAutoAuto--PEEPPEEP

}}

Flow Flow (L/min)(L/min)

Air TrappingAir Trapping



NormalNormalPatientPatient


Air TrappingAir TrappingAutoAuto--PEEPPEEP

}}

Flow Flow (L/min)(L/min)

http://co-5.college-online.com/../../Power%20Point%20Presentations/Flow%20vs%20Time%20Folder/Air%20Trapping%20on%20Flow%20Time%20Scalar.ppt

Airway Resistance Changes

• Causes: – Bronchospasm– Damp or blocked expiratory valve/filter– ETT problems (too small, kinked, obstructed,

patient biting)– High flow– Secretion build-up– Water in the HME

Airway Resistance Changes

• How to ID– Pressure-time: the PIP increases but the plateau stays the

same– Volume-time: it takes longer for the exp curve to reach the

baseline– Flow-time: it takes longer for the exp curve to reach baseline

and the exp flow rate is reduced– FV loop: decreased exp flow with a scoop in the exp curve– PV loop: the loop will be fatter…if it bulges to the right, it’s insp

resistance and to the left it’s exp

• How to fix– ID cause and fix it– Give a tx, sx, drain water, change HME, change ETT, add a bite

block, decrease PF rate, change exp filter

PIP vs PplatPIP vs Pplat

NormalNormal High RawHigh Raw

High FlowHigh Flow Low CLow C LL


PIPPIP

PPplatplat

PIPPIP

PIPPIP PIPPIP

PPplatplatPPplatplat

PPplatplat

PPawaw

(cm H(cm H22O)O)

PIP vs PplatPIP vs Pplat

NormalNormal High RawHigh Raw

High FlowHigh Flow Low CLow C LL


PIPPIP

PPplatplat

PIPPIP

PIPPIP PIPPIP

PPplatplatPPplatplat

PPplatplat

PPawaw

(cm H(cm H22O)O)

http://co-5.college-online.com/../../Power%20Point%20Presentations/Pressure%20vs%20Time%20Folder/PIP%20vs%20%20Pplat%204%20scenarios.ppt

Compliance Changes

• Decreased compliance– Causes

• ARDS• Atelectasis• Abdominal distension• CHF• Consolidation• Fibrosis• Hyperinflation• Pneumothorax• Pleural effusion• Just about every pulm dx there is

– How to ID it• Pressure-time: the PIP and plateau both increase• PV loop: lays more horizontal


Lung Compliance Changes in the P-V Loop


Volume (Volume (mLmL))

PIP levelsPIP levels

VVTT


COMPLIANCENormalIncreasedDecreased

COMPLIANCECOMPLIANCENormalNormalIncreasedIncreasedDecreasedDecreased

Volume Targeted VentilationVolume Targeted Ventilation




Volume (Volume (mLmL))

PIP levelsPIP levels

VVTT


COMPLIANCENormalIncreasedDecreased

COMPLIANCECOMPLIANCENormalNormalIncreasedIncreasedDecreasedDecreased

Volume Targeted VentilationVolume Targeted Ventilation

http://co-5.college-online.com/../../Power%20Point%20Presentations/Pressure%20Volume%20Loop%20Folder/Compliance%20Volume%20Targeted.ppt

Compliance changes

• Increased compliance– Causes

• emphysema• Surfactant therapy

– How to ID it• Pressure-time: PIP and plateau both decrease• PV loop: stands more vertical (upright)

Active Exhalation

• Causes– Patient is exhaling below FRC due to air trapping (vol

dumping)– Pain– Positional change– Equipement calibration problem

• How to ID it– Volume-time: exp waveform goes below the baseline– PV loop: exp loop goes past the zero point– FV loop: exp part goes past the zero point

• How to fix it– Reduce air-trapping– Calibrate equipment– Relieve pain

Partial Obstruction• Causes

– Suction catheter left in ETT– Tissue flap– Mucus plug– Water/secretions in the circuit or airway

• How to ID It– Flow-volume: flow is not steady and constant, but varies as the obst

moves around– PV loop: jagged instead of smooth– FV loop: jagged with fluctuating flow

• How to fix it– Pull catheter out of ETT– Suction– Drain water– Change HME– Move the ETT

Overdistension • Causes

– Vt set too high (vol vent)– Pressure set too high (press

vent)– Could occur in pressure vent

with C or Raw changes

• How to ID it– PV loop: bird beak at the top

of the loop

• How to fix it– Reduce Vt (vol vent)– Reduce pressure (P vent)


OverdistensionOverdistension

Pressure (cm HPressure (cm H22O)O)

Paw rises with little or no change in VT

PPawaw

(cm H(cm H22O)O)


OverdistensionOverdistension

Pressure (cm HPressure (cm H22O)O)

Paw rises with little or no change in VT

PPawaw

(cm H(cm H22O)O)

http://co-5.college-online.com/../../Power%20Point%20Presentations/Pressure%20Volume%20Loop%20Folder/Overdistension.ppt

Leaks • Causes

– Expiratory leak: air leak through a chest tube, BP fistula, ETT cuff leak, NG tube in trachea

– Inspiratory leak: loose connections, ventilator malfunction, faulty flow sensor

• How to ID it– Pressure-time: decreased PIP– Volume-time: decreased Vt…exp leaks keep exp Vt from returning to

baseline– Flow-time: PEF decreases– PV loop: exp side doesn’t return to the baseline– FV loop: exp part doesn’t return to baseline

• How to fix it– ID source of leak and fix it– Do a leak test and make sure all connections are tight

Rate Asynchrony• Causes

– Neurological injury/swelling– Air hunger

• How to ID it– Pressure-time: patient tries to inhale/exhale in the middle of the

waveform, causing a dip in the pressure– Flow-time: patient tries to inhale/exhale in the middle of the waveform,

causing erratic flows/dips in the waveform – PV loop: dips in the loop during either I or E, showing patient efforts to

breathe– FL loop: dips in the loop during either I or E, showing patient efforts to

breathe• How to fix it: if neurological, may need paralytic or sedative to

reduce respiratory drive…if air hunger, adjust settings (try increasing the flow rate/decreasing the It or increasing the set rate to “capture” the patient) or changing the mode - sometimes changing from partial to full support will solve the problem

Flow Asynchrony

• Causes:flow rate set incorrectly for the patient demands (volume vent only…in pressure ventilation the flow is a function of the pressure setting and the patient’s lung characteristics – you don’t set it or have any control over it)

• How to ID It– Pressure-time curve: patient “pulls off” the pressure

curve and it becomes concave – Pressure-volume loop: the inspiratory side will scoop

inward with a decrease in pressure

• How to fix it: increase the peak flow setting

Trigger Asynchrony

• Causes: sensitivity not set correctly…patient has to do excessive work to trigger a breath, autoPEEP

• How to identify it:– Pressure-time curve: there will be a huge negative

deflection before each pressure curve and/or negative pressure deflections that don’t result in a breath delivery

– Flow-time curve: there will be a blip where the patient attempts to trigger

– Pressure-volume loop: there will be a large “pig tail” on the loop

• How to fix it: set sensitivity so that minimal effort is required to trigger the ventilator, eliminate the autoPEEP

Setting the Rise Time

• The faster the flow valve opens, the faster the set pressure is reached in pressure modes

• If the valve opens so fast that the flow is instantaneously delivered to the airway, you can get an overshoot in the pressure curve with ringing (Bart Simpson hair)…you need to increase the rise time if this occurs – this makes the flow valve open a bit more slowly

• If the valve opens too slow, the pressure curve becomes rounded when it should be square in a pressure mode…this will decrease Vt delivery…you need to decrease the rise time if this occurs

Volume-Targeted Ventilation


Controlled Mode (Volume- Targeted Ventilation)


PressurePressure

Volume Volume Volume

FlowFlowPreset Peak FlowPreset Peak Flow

Preset Preset VVtt

Dependent onDependent onCCLL & R& Rawaw


(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)




PressurePressure

Volume Volume Volume

FlowFlowPreset Peak FlowPreset Peak Flow

Preset Preset VVtt

Dependent onDependent onCCLL & R& Rawaw


(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)


Assisted Mode(Volume-Targeted Ventilation)


FlowFlow

PressurePressure

VolumeVolume


(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)




FlowFlow

PressurePressure

VolumeVolume


(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)


SIMV(Volume-Targeted Ventilation)



FlowFlow

PressurePressure

VolumeVolume

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)





FlowFlow

PressurePressure

VolumeVolume

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)


SIMV+PS(Volume-Targeted Ventilation)



FlowFlow

PressurePressure

VolumeVolume

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)

Set PS levelSet PS level





FlowFlow

PressurePressure

VolumeVolume

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)

Set PS levelSet PS level

http://co-5.college-online.com/../../Power%20Point%20Presentations/Modes%20of%20Ventilation/Controlled%20Volume.ppt

Suggested Websites

• www.adhb.govt.nz/newborn/TeachingResources/Ventilation/RespiratoryFunctionMonitoringandGraphics.htm

• www.rtmagazine.com/issues/articles/2002-02_04.asp• www.rcsw.org/Download/2006_RCSW_conf/

Presentation&202006%20RCSW%20Waveforms_in_ARDS%20Dean%20H.pdf

• www.aarc.org/education/webcast/archives/waveforms/03.01.05/ppt#256,1,Using the Ventilator To Probe Physiology: Monitoring Graphics and Lung Mechanics During Mechanical Ventilation

• www.brighamandwomens.org/respiratorytherapy/advmecven2.ppt

http://www.adhb.govt.nz/newborn/TeachingResources/Ventilation/RespiratoryFunctionMonitoringandGraphics.htm

http://www.adhb.govt.nz/newborn/TeachingResources/Ventilation/RespiratoryFunctionMonitoringandGraphics.htm

Documents

Ventilator Graphics