Introducing 

Prezi AI.

Your new presentation assistant.

Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.

Loading…
Transcript

Pressure

Waveform

VENTILATOR GRAPHICS

AND WAVEFORMS

Charles Williams

BSRT,RRT, AE-C

Registered Respiratory Therapist

Lead Therapist at St. Joseph Regional Medical Center

Certified Asthma Educator

NRP Instructor

25+ years in Respiratory Care

I want to

be like Ted

Learner Objectives

Understand the importance of monitoring and interpreting ventilator graphics.

Learn the basic shapes used for waveforms

Identify the different types of waveforms and loops available on most ventilators.

Learn to use the graphics to identify patient/ventilator problems, and make the appropriate adjustments.

Why should we evaluate ventilator graphics and waveforms?

Allows practitioners to evaluate and troubleshoot the patient’s response to the ventilator.

Monitor proper ventilator function.

Monitor the patient’s disease status (Compliance and Airway Resistance)

Assess response to therapy.

Allow fine tuning of ventilator to decrease WOB, optimize ventilation, and maximize patient comfort.

Ventilator graphics reflect the patient-ventilator system and their interaction together.

Learning to analyze and interpret ventilator graphics can be a very useful tool for respiratory therapists.

The graphics can assist therapists in making recommendations and necessary adjustments to the ventilator.

Think of ventilator waveforms as the

EKG for the lungs.

BASIC SHAPES & TYPES

Basic Shapes

The graphics display will have different appearances and configurations, depending on the make and model of ventilator.

SCALERS

Plot pressure, flow, or volume against time.

Time is on the x-axis.

LOOPS

Combine pressure or flow, with volume. There is no time component.

Basic Shapes

Basic Shapes

Generally, The ascending and descending ramps can be considered the same as exponential ramps.

Just remember the three shapes: Square, Ramp, and Sine waves.

SQUARE

Square shapes usually represent a fixed, constant, or set parameter.

RAMPS

Ramps represent a variable. They can be accelerating or decelerating.

SINE

Sine waves are seen with spontaneous, unassisted breathing

Basic Shapes

Question:

What are the 3 basic shapes of waveforms?

Answer:

Square, Ramp and Sine

Pressure

Flow

Volume

Types of Waveforms

Pressure

Types of Waveforms

The pressure waveform displays the amount of pressure generated with each breath.

The Peak Inspiratory Pressure is the highest amount of pressure generated during inhalation. The PIP on this image is about 22 cmH20.

Flow

Types of Waveforms

The flow waveform displays the flowrate associated with each breath. Inspiration is displayed above baseline. Expiration is below the baseline.

In this example, the breath begins at a fast flowrate and then decreases during inspiration.

Volume

Types of Waveforms

The volume waveorm displays the amount of volume inhaled (delivered to the patient), and the amount of volume exhaled (returned to the ventilator).

This patient’s tidal volume is between 350 ml and 400 ml.

Here a a short YouTube video that shows the types of waveforms in realtime

Is it a volume or pressue mode?

Here is an easy way to tell what type of mode (or type of breath) being delivered, just by looking at the graphics.

Look at the pressure waveform and remember the letter “P”. With Pressure breaths…The Pressure waveform…will have a Plateau

For modes such as SIMV/PS, the graphics can show both volume breaths and pressure breaths.

Question:

What are the 3 types of waveforms displayed?

Answer:

Pressure, Flow and Volume

Pressure Waveform

The Pressure waveform can be used to assess:

  • Breath Type (Pressure vs. Volume)
  • Air trapping (auto-PEEP)
  • Airway Obstruction
  • Bronchodilator Response
  • Respiratory Mechanics (Compliance/Raw)
  • Active Exhalation
  • PIP, Pplat
  • CPAP, PEEP
  • Asynchrony
  • Triggering Effort

Pressure Waveform

Pressure Waveform

Pressure Waveform

Setting an inspiratory pause time or (insp. hold maneuver), will create a plateau on the waveform.

The plateau allows for easy visualization of Peak inspiratory pressure (PIP), Plateau pressure (Pplat), and airway resistance (Raw).

Pressure Waveform

Pressing the inspiratory hold button on the ventilator stops air flow.

Since the plateau pressure does not include airway resistance, it is essentially a reflection of pressure measured at the alveolar level.

Pressure Waveform

The baseline for the pressure waveform will be higher when PEEP is added.

When there are patient triggered breaths, there will be a negative deflection at the beginning of the waveform.

Pressure Waveform

While performing an expiratory hold maneuver, trapped air will cause the waveform to rise above the baseline.

Auto-PEEP should be < 5cm H2O.

Pressure Waveform

Increased airway resistance (Raw) will cause the PIP to increase while Pplat remains normal.

Decreased lung compliance will cause the entire waveform to increase in size. The difference between PIP and Pplat will remain normal.

Pressure Waveform

Pressure Waveform

What are we seeing?

Increased airway resistance (Raw)

Flow

Waveform

Flow Waveform

The flow waveform can be used to assess:

  • Air trapping (auto-PEEP)
  • Airway Obstruction
  • I-Time adjustment
  • Bronchodilator Response
  • Active Exhalation
  • Breath Type (Pressure vs. Volume)
  • Inspiratory Flow
  • Asynchrony
  • Triggering Effort

Flow Waveform

A newer feature does allow you to select the desired flow pattern

Flow Waveform

Flow Waveform

This example illustrates how the decelerating flow pattern may be preferred over the constant flow pattern.

The same tidal volume can be delivered to the patient, but with a lower peak pressure.

Flow Waveform

In patients with severe airway obstruction, this can become a problem in flow-cycled modes, such as Pressure Support.

Flow Waveform

If the expiratory portion of the waveform doesn’t return to baseline before the beginning of the next breath, there could be air trapping present (emphysema, improperly set I:E ratio).

Flow Waveform

To assess response to bronchodilator therapy, you should see an increase in peak expiratory flow rate and shorter expiratory times.

Flow Waveform

In Pressure modes that are time-cycled (Pressure Control), the flow waveform should return to baseline.

In Pressure modes that are flow-cycled (Pressure Support), the flow waveform does not return to baseline.

Flow Waveform

This called a "zero-flow" state

Flow Waveform

Question:

What problem are we seeing on this image?

Answer:

Air-trapping or auto-peep

Flow Waveform

Question:

What changes should we see on the flow waveform after administering a bronchodialator?

Answer:

Improved PEF and shorter E-time

Volume

Waveform

Volume Waveform

The volume waveform can be used to assess:

  • Tidal Volume
  • Active Exhalation
  • Asynchrony
  • Airway Resistance
  • Air trapping (auto-PEEP)
  • Leaks

Volume Waveform

Volume Waveform

If the exhalation side of the volume waveform does not return to baseline it could be from a leak, air-trapping or an improperly set inspiratory time.

Volume Waveform

If there is an increase in airway resistance, it may take longer for the exhaled volume to return to baseline.

This is can be seen with a damp or blocked expiratory valve or filter.

Volume Waveform

Question:

The volume waveform is most commonly used to assess which two situations?

Answer:

Air trapping and leaks

Question:

Is this a volume mode or pressure mode of ventilation?

P/V

LOOP

Pressure-Volume loop

The P/V loop can be used to assess:

  • Lung Overdistention
  • Airway Obstruction
  • Bronchodilator Response
  • Respiratory Mechanics (C/Raw)
  • Flow Starvation
  • Leaks
  • WOB
  • Triggering Effort

Pressure-Volume loop

Volume is plotted on the y-axis, Pressure on the x-axis.

Inspiratory curve is upward, 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. It will be at 0 if there’s no PEEP set.

If an imaginary line is drawn down the middle of the loop, the area to the right represents inspiratory resistance and the area to the left represents expiratory resistance.

Pressure-Volume loop

Pressure-Volume loop

(Cdyn)

volume/pressure

If PEEP is added, the loop will begin at the set PEEP level.

The top part of the P/V loop represents dynamic compliance (Cdyn).

Pressure-Volume loop

Pressure modes deliver a set “constant” pressure during inspiration, creating a plateau on the pressure waveform.

This will also create a plateau on the P/V loop.

Pressure-Volume loop

When lung overdistention occurs, pressure continues to increase with little or no change in volume. This can create a “bird beak”.

Pressure-Volume loop

If the patient is triggering the breath, you will see a “crossover” or “tail”, at the beginning of the loop.

As WOB increases, the tail will become larger.

Pressure-Volume loop

Pressure-Volume loop

Decreased Compliance

Increased Compliance

  • Emphysema
  • Post Surfactant therapy
  • ARDS
  • Atelectasis
  • CHF
  • Pleural Effusions

Pressure-Volume loop

Increased Compliance

  • Emphysema
  • Post Surfactant therapy

Decreased Compliance

  • ARDS
  • Atelectasis
  • CHF
  • Pleural Effusions

Pressure-Volume loop

The loop does not completly return to baseline.

Pressure-Volume loop

Point of alveolar opening

Some lung protection strategies for treating ARDS, suggest setting PEEP just above the lower inflection point to hold the alveoli open.

Pressure Waveform

What are we seeing?

Decreased lung compliance

F/V

LOOP

Flow-Volume loop

The F/V loop can be used to assess:

Air trapping

Airway Obstruction

Airway Resistance

Bronchodilator Response

Insp/Exp Flow

Leaks

Water or Secretion accumulation

Flow Starvation

Asynchrony

Flow is plotted on the y axis and volume on the x axis

Flow-Volume loop

Flow-Volume loop

Flow volume loops used for ventilator graphics are usually shown upside down.

Inspiration is above the horizontal line and expiration is below

The shape of the inspiratory portion of the curve will match the flow waveform.

The shape of the exp flow curve represents passive exhalation.

Looks circular with spontaneous breaths

Flow-Volume loop

Flow-Volume loop

The shape of the inspiratory portion of the curve will match the flow waveform.

Flow-Volume loop

Airway Obstruction

With conditions that cause airway obstruction (asthma, COPD), you may see a lower peak expiratory flow (PEF).

You may also see “scooping” on the expiratory portion of the loop. Scooping because visible due to airway obstruction.

This is how a Flow-volume loop appears on a Pulmonary Function Test

Flow-Volume loop

Airway Obstruction

The F-V loop usually appears “upside down” on most ventilators.

Flow-Volume loop

Air trapping or leaks

If there is air-trapping, or a leak, the loop will not return to the starting point

Flow-Volume loop

Water or Secretions in circuit

If there is a collection of water in the ventilator circuit or a build up of secretions, you may see a jagged, “sawtoothed” pattern.

What 2 things are we seeing?

Scooping and Decreased PEF

Flow-Volume loop

What are we seeing?

Leak or air trapping

Flow-Volume loop

Asynchrony & Troubleshooting

The inspiratory portion of the pressure waveform shows a “dip”.

Because of an inadequate flowrate , the patient's inspiratory effort causes a drop in tge pressure being measured. This is also know as "Flow mismatching"

Asynchrony

Some ventilators may have an adaptive flow system that will automatically increase flow to try and meet the patient’s demand.

Notice that on the next breath, the flowrate has been increased.

Asynchrony

Any “dips” or irregular shaped loops can be an indication of asynchrony.

Asynchrony

Asynchrony

Causes: (Flow, Rate, or Triggering)

Air hunger (flow starvation)

Neurological Injury

Improperly set sensitivity

How to identify it on the graphics:

Pressure waveform: Patient tries to inhale/exhale in the middle of the waveform, causing a dip in the pressure

Flow waveform: Patient tries to inhale/exhale in the middle of the waveform, causing erratic flows/dips in the waveform

Pressure/Volume loop: Patient makes effort to breath causing dips on either inspiratory or expiratory side.

Flow/Volume loop: Patient makes effort to breath causing dips in loop on either inspiratory or expiratory side.

How to fix it:

Try increasing the flow rate, decreasing the I-time, or increasing the set rate to “capture the patient” to better meet the patient’s needs.

Change the mode - sometimes changing from partial to full support will solve the problem.

If neurological, may need paralytic or sedative.

Adjust sensitivity

Air Trapping or AutoPeep

Causes:

Insufficient expiratory time

Early collapse of unstable alveoli/airways during exhalation

How to Identify it on the graphics:

Pressure waveform: While performing an expiratory hold, the waveform rises above baseline.

Flow waveform: The expiratory flow wave doesn’t return to baseline before the next breath begins.

Volume waveform: The expiratory portion doesn’t return to baseline.

Flow/Volume Loop: The loop doesn’t return completely to baseline

Pressure/Volume Loop: The loop doesn’t return completely to baseline

How to Fix:

Give a bronchodilator treatment, adjust I-time, increase flow, adjust PEEP.

Airway Resistance Changes

Causes:

Bronchospasm

ETT problems (too small, kinked, obstructed)

High flow rate

Secretion build-up

Damp or blocked expiratory valve/filter

Water in the HME

How to identify it on the graphics:

Pressure waveform: PIP increases, but the plateau stays the same

Flow waveform: It takes longer for the exp side to reach baseline

Volume waveform: It takes longer for the exp curve to reach the baseline

Pressure/Volume loop: The loop will be wider. Bulge to the left = exp resistancw, bulge to right = insp resistance.

Flow/Volume loop: decreased exp flow, scooping on the exp curve

How to fix:

Give a bronchodilator treatment, suction patient, drain water, change HME, change ETT, add a bite block, reduce flowrate, change exp filter.

Compliances Changes

Decreased compliance

Causes:

ARDS

Atelectasis

Abdominal distension

CHF

Consolidation

Fibrosis

Overdistention

Pneumothorax

Pleural effusion

How to identify it on the graphics:

Pressure wave: PIP and plateau both increase

Pressure/Volume loop: lays more horizontal

Increased compliance

Causes:

Emphysema

Surfactant Therapy

How to identify it on the graphics:

Pressure wave: PIP and plateau both decrease

Pressure/Volume loop: Stands more vertical (upright)

Leaks

Causes:

Expiratory leak: ETT cuff leak, circuit connections, chest tubes, BP fistula, NG tube in trachea

Inspiratory leak: Loose connections, faulty flow sensor, ventilator malfunction

How to identify it on the graphics:

Volume waveform: Expiratory side of wave doesn’t return to baseline

Flow waveform: PEF decreased

Pressure/Volume loop: Exp side doesn’t return to the baseline

Flow/Volume loop: Exp side doesn’t return to baseline

How to fix it:

Check possible causes listed above

Do a leak test and make sure all connections are tight

Rise Time &

Insp Cycle Off %

Rise Time & Insp Cycle Off %

Rise Time

Insp Cycle

Off %

Rise Time

Rise Time

The inspiratory rise time is the time it takes to reach full inspiratory flow, or pressure, at the start of each breath.

The rise time can be expressed as a percentage of the breath cycle time (%) or in seconds (s).

Rise Time

If rise time is set too fast, you can get an overshoot in the pressure wave, creating a pressure “spike”.

If this occurs, you need to increase the rise time. This will make the flow valve open more slowly.

Rise Time

1. Here we can see the “spike” on our graphics.

2. The rise time is set at .05 seconds

Rise Time

4. The waveform will return to normal

3. Increasing the rise time will open the

valve slower

Rise Time

If rise time is too slow, the pressure waveform will become more slanted, when it should look more square. This may affect Vt delivery and may not meet the patient’s inspiratory demands.

If this occurs, you will need to decrease the rise time to open the valve faster.

Inspiratory Cycle off %

Also know as:

Inspiratory cycle threshold

Inspiratory flow termination,

Expiratory flow sensitivity,

Inspiratory flow cycle %,

E-cycle, etc…

In flow-cycled modes, like Pressure Support & Volume Support, the inspiratory cycle off % determines when the ventilator cycles from inspiration to expiration.

Inspiratory Cycle off %

In flow-cycled modes, like Pressure Support & Volume Support, the inspiratory cycle off % determines when the ventilator cycles from inspiration to expiration.

100%

50%

Peak Insp Flow

(PIF)

30%

Inspiratory Cycle off %

60%

10%

Setting the percentage lower, will cycle inspiration off later.

This may make the breath too long. If so, you may see an expiratory spike.

Setting the percentage higher, will cycle inspiration off sooner.

This could make the breath too small, effecting tidal volume

Rise Time

What are we seeing here?

Rise time is too slow

SOURCES

SOURCES:

Rapid Interpretation of Ventilator Waveforms, Waugh, Harwood, and Deshpande

Ventilator Waveform Analysis, Pearson

Anatomy of Servo-i Graphics, Maquet, inc.

Golden Moments in Mechanical Ventilation, Maquet, inc

Waugh, Jonathan B. Rapid Interpretation of Ventilator Waveforms. Pearson Prentice Hall, 2007.

Bill Pruitt, “Ventilator Graphics Made Easy / RT.” RT: For Decision Makers in Respiratory Care, www.rtmagazine.com/2007/02/ventilator-graphics-made-easy/.

American Thoracic Society - Ventilator Waveform Interpretation and Analysis, www.thoracic.org/professionals/clinical-resources/critical-care/clinical-education/mechanical-ventilation/ventilator-waveform-analysis.php.

“Ventilator Graphics Made Easy.” AARC, www.aarc.org/webcasts/ventilator-graphics-made-easy/.

Thank You!!!

Learn more about creating dynamic, engaging presentations with Prezi