Ventilator Graphics v3.0
Charles Williams RRT, AE-C
Learner Objectives
Understand the importance of monitoring and interpreting ventilator graphics. Learn the basic shapes of 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 do we monitor 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 are waveforms that reflect the patient-ventilator system and their interaction.
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.
Practitioners can use ventilator graphics to assess the condition of a patient’s lungs in the same way a cardiologist uses the graphics of an EKG to view the condition of the heart.
Puritan Bennett 840 ®
Hamilton Galileo ®
Drager Evita ® Respironics Esprit ®
The graphics display will have different appearances and configurations, depending on the make and model of ventilator.
Basic Shapes of Waveforms
Scalars Time
Loops
Basic waveforms that plot pressure, flow, or volume against time. Time is on the x-axis. Waveforms that combine pressure or flow, with volume. (P/V or F/V). There is no time component.
Basic Shapes of Waveforms
Generally, The ascending and descending ramps can be considered the same as exponential ramps, So you really only need to remember three shapes: Square, Ramp, and Sine waves.
Basic Shapes of Waveforms
Squares
Ramps
Sine
Squares represent fixed, constant, or set parameters. For example, pressure setting in Pressure Control mode. Ramps represent variables. Will vary with changes in lung characteristics. Ramps can be accelerating or decelerating. Sine waves are seen with spontaneous, unassisted breathing.
Basic Shapes of Waveforms Question: What are the three basic shapes of waveforms? Answer: Square Ramp Sine
Types of Waveforms
3
Each time the ventilator delivers a breath, there are waveforms that are displayed on the graphics screen: Pressure, Flow, and Volume.
Types of Waveforms
(20)
The pressure scalar displays the amount of pressure generated with each breath. The scale is located on the left side in cmH20. The peak pressure of these breaths are about 22 cmH20.
Types of Waveforms
The flow scalar displays the flowrate, or speed associated with each breath. In this example, the breath begins at a fast flowrate and then decreases during inspiration.
Types of Waveforms
(375 ml)
(250 ml)
Volume in
Volume out
The volume scalar displays the amount of volume inhaled and exhaled with each breath. The scale is located on the left side in ml’s. These breaths are about 370 ml.
Types of Waveforms Question: What 3 waveforms are displayed on the graphics screen? Answer: Pressure
Flow Volume
Types of Waveforms
Pressure Modes
Volume Modes Pressure
Pressure
square
Flow
Flow
square
Volume
Volume
Volume Control SIMV (Vol. Control)
Pressure Control *PRVC SIMV (PRVC) SIMV (Press. Control)
Pressure Support *Volume Support
* Considered a “dual-mode” of ventilation
Types of Waveforms Volume Modes
Pressure Modes
Pressure
Pressure
Flow
Flow
Note: Some ventilators allow you select the desired flow pattern for different modes.
Types of Waveforms SIMV (Vol. Control) + Pressure Support
Volume Breath
Pressure Breath
Pressure Breath
Volume Breath
For combination modes, such as SIMV/PS, the graphics can show both volume breaths and pressure breaths.
Pressure Waveform Pressure Modes
Volume Modes Pressure
Pressure
square
Flow
Flow
square
Volume
Volume
Volume Control SIMV (Vol. Control)
Pressure Control PRVC SIMV (PRVC) SIMV (Press. Control)
Pressure Support Volume Support
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 Volume Modes
Pressure Modes
If the ventilator delivers a volume breath, the shape of the pressure waveform will be a ramp.
If the ventilator delivers a pressure breath, the shape of the pressure waveform will have a square shape.
square
Ramp = variable
Square = constant
Pressure Waveform Volume Modes
Pressure Modes
This means that pressure will vary, depending on lung characteristics; (compliance, airway resistance, etc.)
This means that pressure will remain the same during inspiration.
Ramp = variable
Square = constant
Pressure Waveform Pressure waveform
Pressure waveform with “inspiratory pause” PIP
Pplat
Raw
Setting an inspiratory pause time or performing an insp. hold maneuver, will create a plateau on the waveform. The plateau allows for easy visualization of PIP, Pplat, and Raw. Adding an inspiratory pause time may improve distribution of ventilation.
Pressure Waveform I-time Peak Inspiratory Pressure (PIP) Plateau Pressure (Pplat) Alveolar Distending Pressure
Elastic Recoil Pressure
= Mean Airway Pressure (MAP)
Pressure Waveform
10 5
PEEP
PEEP No patient effort
PEEP Patient triggered breath
The baseline for the pressure waveform will be higher, when Positive EndExpiratory Pressure (PEEP), is added. PEEP is also a component of mean airway pressure (MAP). With patient triggered breaths, there will be a negative deflection just before the waveform.
Pressure Waveform
I-time
Peak Inspiratory Pressure (PIP)
Pressure Waveform Increased Airway Resistance (Raw) PIP
Decreased Compliance PIP
(Increased Raw) Pplat
(Normal Raw) Pplat
Increased airway resistance (Raw) will cause the PIP to increase. The Pplat pressure 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 Air-Trapping (auto-PEEP)
“Expiratory hold” maneuver
PEEP
auto-PEEP (trapped air) PEEP
auto-PEEP Set PEEP
Total-PEEP
+9 +5 +14
While performing an expiratory hold maneuver, trapped air will cause the waveform to rise above the baseline. An acceptable amount of auto-PEEP should be < 5cm H2O.
Pressure Waveform Label the parts: A
B C =G
E
F
A= Inspiratory Time
D= Airway Resistance (Raw)
B= Peak Insp. Pressure (PIP)
E= Alveolar Distending Pressure
C= Plateau Pressure (Pplat)
F= Elastic Recoil Pressure
G= Mean Airway Pressure (MAP)
Pressure Waveform Question: What does this pressure waveform show?
Answer: Increased airway resistance
Flow Waveform Pressure Modes
Volume Modes Pressure
Pressure
square
Flow
Flow
square
Volume
Volume
Volume Control SIMV (Vol. Control)
Pressure Control PRVC SIMV (PRVC) SIMV (Press. Control)
Pressure Support Volume Support
Flow Waveform If a volume breath is delivered, the shape of the waveform will be a square. This means that the flowrate stays the same during inspiration.
If a pressure breath is delivered, the shape of the waveform will be a ramp. This means that the flowrate starts out high and then decreases during inspiration.
Square = constant
Ramp = variable
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 Volume Modes
I-time
Pressure Modes
I-time Set Flowrate
E-time
PEF
PIF
E-time
PEF
Flow Waveform
The decelerating flow pattern may be preferred over the constant flow pattern. The same tidal volume can be delivered, but with a lower peak pressure.
Flow Waveform Airway Obstruction PIF
Inspiratory flow takes longer to return to baseline
= Normal PEF
In patients with severe airway obstruction, the flow waveform can become a plateau. This can become a problem in flow-cycled modes, such as Pressure Support. (asynchrony, W.O.B.)
Flow Waveform Auto-Peep (air trapping)
Expiratory flow does not return to baseline
= Normal
Start of next breath
If the expiratory portion of the waveform doesn’t return to baseline before the start of the next breath starts, there could be air trapping. (emphysema, improperly set I:E ratio).
Flow Waveform Bronchodilator Response Pre-Bronchodilator
Post-Bronchodilator
I-time
Prolonged E-time
Normal E-time
Reduced PEF Improved PEF
To assess response to bronchodilator therapy, you should see an increase in peak expiratory flow rate. Also, the expiratory portion of the curve should return to baseline sooner.
Flow Waveform
Pressure Control, PRVC (Time-cycled)
Adjusting I-Time
Pressure Support, Volume Support (Flow-cycled)
Pressure
Flow
Inspiration should end when flow reaches baseline
Inspiration ends before flow reaches baseline
Volume
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. (Adjustment is made with Insp. Cycle Off %)
Flow Waveform Adjusting I-Time I-time
I-time
(Too short)
(Too long)
Inspiration should end here
Not here
Inspiration should end here
Not here
Remember, this applies to Control modes with a decelerating flow (ramp). This includes Pressure Control, PRVC, SIMV (Press. Control), and SIMV (PRVC). Volume Control and SIMV (Vol. Control) have a constant flow.
Flow Waveform Question: What does this flow pattern show?
Answer: Air trapping (auto-PEEP)
Flow Waveform Question: To assess improvement after a breathing treatment you should see what? Pre-Bronchodilator
Post-Bronchodilator
I-time
Normal E-time
Improved PEF
Answer: Improved PEF and shorter E-time
Volume Waveform Pressure Modes
Volume Modes Pressure
Pressure
square
Flow
Flow
square
Volume
Volume
Volume Control SIMV (Vol. Control)
Pressure Control PRVC SIMV (PRVC) SIMV (Press. Control)
Pressure Support Volume Support
Volume Waveform Volume Modes
The Volume waveform will generally have a “mountain peak” shape regardless of what mode, of ventilation.
Pressure Modes
There may also be a small plateau at the top of the 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
Inspiratory Tidal Volume Exhaled volume should return to baseline
Volume Waveform Air-Trapping or Leak
Volume Loss
If the exhalation side of the waveform doesn’t return to baseline, it could be from air-trapping (improperly set I-time, emphysema), or there could be a leak (ET tube, vent circuit, chest tube, etc.)
Volume Waveform Increased Airway Resistance = Normal
Exhaled volume taking longer to get out
If there is an increase in airway resistance, it will take longer for the exhaled volume to return to baseline. This is more commonly seen with a damp or blocked expiratory filter/valve.
Volume Waveform Question: The volume waveform is most commonly used to assess which two situations?
Answer: Air trapping and leaks
Is it Volume or Pressure? Pressure Modes
Volume Modes
Pressure
Pressure
Flow
Volume
square
square
Flow
Volume
Here is an easy way to tell what type of mode (or type of breath) this is, 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.
Is it Volume or Pressure? The pressure waveform has a plateau
The flow waveform doesn't return to baseline
Is it a Volume or Pressure mode? (Hint: look at the pressure waveform) Is it a Control mode or Support mode? (Hint: look at the flow waveform)
Volume Modes
Pressure Modes
Ventilator Graphics
PressureVolume Loops
Pressure-Volume Loops
• 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 Loops
The Pressure/Volume Loop can be used to assess: Lung Overdistention Airway Obstruction Bronchodilator Response Respiratory Mechanics (C/Raw) Flow Starvation Leaks WOB Triggering Effort
Pressure-Volume Loops
Volume Modes
In Volume modes, the P/V loop will normally have a “football” shape.
Pressure Modes
In Pressure modes, the P/V loop will have a “square” appearance.
Pressure-Volume Loops
Dynamic Compliance (Cdyn)
500
250
5
10
15
20
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). Cdyn = Δvolume/Δpressure
Pressure-Volume Loops
500
Plateau
250
10
20
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 Loops Overdistention
“beaking”
500
250
10
20
Pressure continues to increase with little or no change in volume, creating a “bird beak”. Fix by reducing amount of tidal volume delivered.
Pressure-Volume Loops Triggering Effort
WOB
tail
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 Loops Airway Resistance 500
Increased expiratory resistance: secretions, bronchospasm, etc.
250
Increased inspiratory resistance: 10
20
ETT size too small, tube kinked, patient biting tube, etc.
As airway resistance increases, the loop will become wider. An increase in expiratory resistance is more commonly seen.
Pressure-Volume Loops
Increased Compliance
Decreased Compliance
Cdyn 500
500
250
250
Cdyn
10
20
10
20
Cdyn = Dynamic Compliance Examples: Examples: (Δvolume/Δpressure) Emphysema, ARDS, CHF, Post Surfactant Therapy Atelectasis, Pleural Effusions
Pressure-Volume Loops
Increased Compliance
Decreased Compliance
600/12 Cdyn = 50 ml/cmH20
600
500
500
Increased volume
300/22 Cdyn = 14 ml/cmH20
300
250
250 Decreased volume
12 Decreased pressure
10
22
20
10
Increased pressure
20
VT – (Tubing compliance) Examples: Examples: Cdyn = PIP - PEEP Emphysema, ARDS, CHF, Post Surfactant Therapy Atelectasis, Pleural Effusions
Pressure-Volume Loops A Leak 500
250
10
20
The expiratory portion of the loop does not return back to baseline. This indicates that there is a leak.
Pressure-Volume Loops point of alveolar collapse
Upper Inflection Point Third Inflection Point
500
250
Lower Inflection Point 10
point of alveolar opening
20
Inflection Points Some lung protection strategies for treating ARDS, suggest setting PEEP just above the lower inflection point, to hold the alveoli open.
Pressure-Volume Loops
500
250
10
20
Question: What does this loop show? Answer: Decreased lung compliance. (ARDS, CHF, Atelectasis)
Pressure-Volume Loops
500
250
5
15
30
Question: What is happening when there is a bird beak appearance on the P/V loop? Answer: Lung overdistention. Pressure continues to increase, with no increase in volume.
Pressure-Volume Loops
Question: What does this P/V loop show? Answer: Increased expiratory airway resistance (Raw).
Ventilator Graphics 40 20 200 0 20
FlowVolume Loops
40
600
Flow- Volume Loops
• Flow is plotted on the y axis and volume on the x axis • Flow volume loops used for ventilator graphics are the same as ones used for Pulmonary Function Testing, (usually 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. • Can be used to determine the PIF, PEF, and Vt • Looks circular with spontaneous breaths
Flow-Volume Loops The Flow/Volume 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-Volume Loops 60
40
20
0
Begin Inspiration 200
Begin Expiration 400
600
-20
-40
-60
Peak Expiratory Flow (PEF)
Flow-Volume Loops Constant Flow
0
Variable Flow
0
The shape of the inspiratory portion of the curve will match the flow waveform.
Flow-Volume Loops PEF
Airway Obstruction Reduced PEF “scooping”
0
PFT view
0
With conditions that cause airway obstruction (asthma), you will see a lower peak expiratory flow (PEF). You should also see “scooping” on the expiratory portion of the loop. *Scooping means that the volume is being exhaled at a slower rate because of obstruction.
Flow-Volume Loops Airway Obstruction
0
Ventilator graphic view
0
“scooping”
Reduced Peak Flow (PEF)
The F-V loop appears “upside down” on most ventilators.
Flow-Volume Loops 60
Air Trapping or Leaks 40
20
0 200
400
600
-20
loss of volume -40
= Normal -60
If there is air-trapping, or a leak, the loop will not meet at the starting point where inhalation starts and exhalation ends.
Flow-Volume Loops Water or Secretions
If there is a collection of water in the ventilator circuit or a build up of secretions, you will see a jagged, “sawtoothed” pattern.
Flow-Volume Loops
20
0
Begin Inspiration 200
-60
400
Begin Expiration 600
Peak Expiratory Flow (PEF)
What points on this F/V loop do the arrows indicate?
Flow-Volume Loops 60
40
20
0 200
400
600
-20
-40
-60
Question: What does this F/V loop show? Answer: There is air-trapping or a leak. (ETT cuff, vent circuit)
Flow-Volume Loops
0
0
Question: What is the term used to describe the part of the loop indicated by the arrow? What causes it? Answer: This is known as “scooping”. It’s caused by small airway obstruction.
Asynchrony (out of sync)
Flow Starvation
The inspiratory portion of the pressure waveform shows a “dip”. Because of an inadequate flowrate , the patient is “sucking in” attempting to get more air. This causes a drop in pressure. A main disadvantage of constant flow modes (e.g. Volume Control), is that it may not meet the patient’s inspiratory demands.
Asynchrony (out of sync) “Dip”
Flow Starvation Ventilator detects inadequate flow
Some ventilators 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 (out of sync)
F/V Loop
P/V Loop
Any “dips” or irregular shaped loops are an indication of asynchrony.
Air-Trapping (auto-PEEP) 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. Increased insp. resistance will cause it to bulge to the right. Increased exp resistance will cause it to bulge to the left. • 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.
Compliance 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 , chest tube leak, BP fistula, NG tube in trachea • Inspiratory leak: Loose connections, ventilator malfunction, faulty flow sensor
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
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
The pressure waveform does have a plateau, but it’s from an insp. hold or set insp. pause.
square
Is this a Volume or Pressure mode?
Ventilator Graphics
Adjusting 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 The Bart Simpson “spike” Rise time “overshoots” desired pressure
Too fast
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 makes 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
3. When we increase the rise time, thus
4. …the waveform will return to
making it slower…
normal.
Rise Time
Too slow
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 % (Flow – Cycling)
In flow-cycled modes, like Pressure Support & Volume Support, the inspiratory cycle off % determines when the ventilator cycles from inspiration to expiration. Also know as: •Inspiratory cycle threshold •Inspiratory flow termination, •Expiratory flow sensitivity, •Inspiratory flow cycle %, •E-cycle, etc…
Inspiratory Cycle off % (Flow – Cycling)
pressure
Inspiration ends
flow
The inspiration ends when inspiratory flow has dropped to a specific flow value.
Inspiratory Cycle off % (Flow – Cycling)
Peak Inspiratory Flow (PIF) 100% 75%
Flow
50% 25%
30%
In the above example, the ventilator is set to stop inspiration and begin expiration, at 30% of the patient’s peak inspiratory flow (PIF).
Inspiratory Cycle off % (Flow – Cycling)
The ventilator will cycle off inspiration at this point…
…and then begin expiration
Inspiratory Cycle off % (Flow – Cycling)
Exhalation “spike”
100%
100%
60% 10%
The cycle off percentage is too high (60%), cycling inspiration off too soon.
The cycle off percentage is too low (10%), This makes the breath too long.
This makes the breath too small. (not enough Vt.)
This forces the patient to actively exhale against the breath, creating a pressure “spike”. (increases WOB),
Rise Time Question: What does this waveform show?
Answer: Rise time is too slow
Inspiratory Cycle off % (Flow – Cycling)
Question: This pressure support breath is set to insp. cycle off at 80%, 50%, 30%, or 10%? 100%
Flow
75% 50% 25%
Answer: 30%
Sources: • Rapid Interpretation of Ventilator Waveforms, Waugh, Harwood, and Deshpande
• Ventilator Waveform Analysis, • Anatomy of Servo-i Graphics, Maquet, inc. • Golden Moments in Mechanical Ventilation, Pearson
Maquet, inc.
Ventilator Graphics
Me using the flow waveform to adjust I-time
Thank You!