Ventilator Graphics

Graphics are waveforms that reflect the patient-ventilator system and their interaction
Role of ventilator wave forms
. Identify pathophysiologic processes
. Recognize patients response to therapy and monitors patients disease status
. Calculate respiratory mechanics
. Optimise ventilator settings and treatment
. Determine effectiveness of ventilator settings
. Detect adverse effects of mechanical ventilation
. Minimize risk of ventilator induced complications - Allows user to interpret,
   evaluate, and troubleshoot ventilator and patients' response to ventilator

Ventilator Graphic classification
1) Scalar graphic - Any single variable (eg-Flow, pressure, volume) plotted
   against time.
a) Flow vs time scalar
b) Pressure vs time scalar
c) Volume vs time scalar

2) Loops - The two dimensional graphic display of two scalars
a) Pressure-Volume loop
b) Flow-Volume loop

Pressure waveforms
. Rectangular waveform
. Exponential rise wave form
. Sine wave form





.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)

To Increase Mean Airway Pressure
1. Increase flow
2. Increase peak pressure
3. Lengthen inspiratory time
4. Increase PEEP
5. Increase Rate

















.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 inspiratory flow curve will match what's set on the ventilator
.The shape of the expiratory flow curve represents passive exhalation.it's long and more drawn out in patients with less recoil
.Can be used to determine the PIFR, PEFR, and Vt
.Looks circular with spontaneous breaths
.Looks squared but set at an angle with PC/PS breaths

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









.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















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 higher the lung compliance, the more horizontal it lays, the lower the lung compliance. Thus slope of the line equals compliance.
.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


Example -
Inspiratory WOB-Increased secretion, Kinked or partially blocked tube.
Expiratory WOB - Bronchospasm , BPD lung







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