ARTP 07 Basic Vent Function Flashcards
What is our normal physiological pressure of ventilation?
Negative pressure
Internal circuit
Pathway for air inside on it way to the external circuit
External circuit
Pathway for air through the inspiratory side to the patient then through the expiratory side back to the ventilator
Exhale valve
Functions to direct flow of the gas towars patient
Valve closes on inspiration
a functional exhale valve is required for the delivery of PEEP
2 types of negative pressure machines
Chest cuirass
Iron lung
PIP/MIP (peak inspiratory pressure) (Maximal inspiratory pressure)
Pressure it takes to vent lung. Also known as PAP (peak airway pressure)
Required to deliver a set volume.
MAP (Mean airway pressure)
Average airway pressure over the respiratory cycle
Sensitivity (trigger)
Pt effort needed to trigger ventilation.
Flow trigger sensitivity is more responsive to pt effort.
I:E ratio
1:2
I:E is manipulated with flow
Inverse I:E
Inspiratory time greater than expiratory time
Can be used for infants and adults who are critically ill.
Can be used to treat refractory hypoxia
What trigger is easiest for patients?
Flow trigger
Trigger
Starts inspiration
Cycle
Ends inspiration
Spontaneous
Inspiration is patient triggered and cycled
Mandatory
Inspiration is machine triggered or cycled
Alternate name for spontaneous
Pressure support
Alternate names for Mandatory
AC (assist/control)
Control
Mechanical
SIMV
When do exhalation valve open?
At the end of cycle
Control variable
What vent manipulates to deliver a breath (pressure or volume)
Volume control
Tidal volume and flow are preset
Volume is constant, pressure varies
Pressure control
Inspiratory pressure is preset
Pressure is constant and volume varies
CMV (continuous mandatory ventilation)
Control
Machines is set to deliver all breaths based on time
Patient CANNOT take assisted breaths
Assist/ control
Patient can take assisted breaths if breathing over a set rate. Patient can trigger or machine will trigger depending on rate.
Sensitivity is adjusted to allow patient breath at a set rate VT in volume control or set PIP in pressure control
IMV/ intermittent mandatory ventilation or SIMV
Combination of mandatory breaths from the vent, but the patient can also take spontaneous breaths between vent breaths. Spontaneous breaths are delivered at a volume the patient desires.
Support modes
Vent provides the work for the patient
Assist control
SIMV + PSV
A/C
Spontaneous
Patient is in control and does the work
Pressure support, PSV and CPAP
Trigger variable
What starts the breath
Target variable
An upper boundary set which doesn’t terminate inspiration but is maintained at pressure, volume, or flow
Cycle variable
What ends inspiration
4 phases of breath
Change of expiration to inspiration
Inspiration
Change from inspiration to expiration
Expiration
Pressure triggered
The patient generates inspiration from changing pressure.
Sensitivity is set to -0.5 to -2 cmH2O
Flow cycled
Inspiration ends when a minimum flow is reached
In “pressure support mode” the inspiratory pressure ends when inspiratory flow descreases to a certain level.
Where is flow cycled found
Only in pressure support mode
Time cycled
Inspiration ends due to a set time for inspiration
If pip is reached, the machine holds inspiration until inspiratory time hs expired
When is time cycled used?
Used in adults with inverse ratio ventilation on occasion
Pressure limited
Reaches the pressure and holds that pressure until some cycling mechanism ends inspiration
Pressure limit is a setting
Pressure limit relief (safety pressure limit) (high pressure alarm limit)
Vent will alarm and cycles inspiration off and releases gas when pressure limit is reached
Inflation hold/ plateau
At peak inspiration, holds pressure or volume. 0.5 to 2 sec
I:E limit
Prevents vent from delivering an I:E ratio greater than 1:1
PEEP (positive end expiratory pressure)
Positive pressure held at an elevated baseline above atmospheric pressure
Helps increase PaO2
Aka facilitate oxygenation
Keeps alveoli open
What modes use PEEP?
A/C or IMV/SIMV
Physiological effect of PEEP?
Causes decreased venous return to heart and possible decreased blood pressure (CAN BE USED TO TREAT PULM EDEMA)
Increase FRC and decreased shunting
Increase airway pressure
Increase peep
Increased pao2 to allow for decreased levels of FiO2 to be used
CPAP Continuous positive airway pressure
A purely spontaneous mode, cannot be used for patients that are apneic
Used to aid in elevating PaO2 and does not remove PaCO2
Patient must be able to spontaneously ventilate.
Key factors in choosing flow pattern?
Best ventilate the patient
Provide low PIP
Lowest MAP
I:E ratio of at least 1:2
Sine wave
Like normal breathing
Flow is not constant
Square wave
Inspirstory flow is constant
Could increase peak airway pressure and mean airway pressure
Tapered/decelerating/ rape waveform
Flow rate on inspiration is high then tapers off
Helps reduce risk of barotrauma
How does increased/ decreased flow affect I:E time
Increased flow: decreased I time, increased E time
Decreased flow: increased I time, decreased e time
How does volume effect I:E time
Increased volume: increased i time, decreased e time
Decreased volume: decreased i time, increased e time
How does rate affect I:E time
Increased rate: decreased i time, decreased e time
Decreased rate: increased i time, increased e time
Spontaneous breaths?
Patient triggered and patient cycled
Mandatory breaths?
Machine trigger and maching cycled
Patient triggered and machine cycled
CMV or assist/control
Interchangeable terms
Deliver mandatory breaths
CMV
Each breath delivered is a set volume or pressure
CMV or control, the patient CANNOT take a spontaneous breath
IMV/ SIMV
The vent will deliver a mandatory breath and the patient can initiate a spontaneous breath.
CSV
Continuous spontaneous vent all breaths are initiated and cycled by the patient
Inverse I: E ratio is used when
Used when a patient is very critical and maximum levels of O2 and PEEP are not improving patients oxygenation.
IMV/ SIMV
Not a full support mode
Used as a weaning mode
transtion to full weaning mode
Will IMV have a set rate and if so can patient take spontaneous breaths?
Yes, and in between the set number of breaths the patient can take as many spontaneous breaths as needed
Main difference between simv and imv?
SIMV will not stack breath’s
What breathing mode is used for weaning and known as a spotter?
PSV
PSV (pressure support ventilation)
Purely spontaneous. Patient must be able to spontaneously breath
Patient triggers the machines
What type of cycle is PSV
Flow cycled
What levels compensate for the airway resistance of an artificial airway and tubing?
5-7 cm H2O
How does PSV help?
Decreased WOB Can increase spontaneous tidal volume Can decrease RR Can increased VT Reduces respiratory muscle activity Can decrease O2 consumption (good for COPD)
What is your goal of PSV?
Maintain spontaneous VT of 4-8 ml/kg IBW
Decrease RR < than 30 bpm
Decrease WOB
If you want to increase spontaneous tidal volume with ps what do you do?
Increase PS until volumes near your desired level.
If your goal is to overcome RAW what do you do with PS?
Increase pressure support level until work of breathing decrease and vent pattern improves
Pressure support will not do all of the work for them, will help w increasing spontaneous tidal volume
Pressure support mimics our normal breaths
What mode if a patient is not breathing spontaneously or not strong enough to initiate an assisted breath?
Assist/control or CMV
What mode if patient is strong enough to assist vent in Assist/control?
SIMV
Patient whose tidal volume is large but has low PaO2?
Try PEEP or CPAP
Patient strong enough to assist vent but has low VT in spontaneous breaths
PSV
Who does flow triggering help?
All patients
When oxygenation is poor and pressure control does not work?
Inverse ratio ventilation
