Test 9 Flashcards
Volume varies with changes in compliance and resistance but pressure remains constant
Pressure Control
Decrease in lung compliance will receive consistent volume and flow but pressure will increase
Volume Control
Used to calculate volume
Flow Control
Pressure, Volume, and Flow are dependent
Time Control
Square Flow Pattern
Inspiratory flow rises rapidly to a preset level and stays at that level until expiration begins
-Shortest Ti, less effects on heart, higher pk pressures
Sine Flow pattern
Sinusoidal, Flow gradually increases and decreases throughout inspiration
Sets of I:E ratio alarm
Obstruction, inadequate volume being delivered, apnea
Pressure Alarms cause
Obstruction, Leaks, AutoPEEP
Flow Alarms cause
Hyperventilation, Hypoventilation, Auto Triggering
Volume Alarms cause
Leak in circuit, cuff leak
Time alarms cause
Hyperventilation, Apnea
Triggering rules
set as sensitive as possible
Pressure: -0.5 to -2.0
Flow: 2-3 below base flow
Inspiration Time
Ti about 1 sec normal (0.8-1.2)
at least a 1:2 ratio
I:E
The shorter the I time the longer the E time, lower MAP
-Longer E time allows for gas exchange, as well as air trapping
Inverse ratio
used on pts with ARDS or restrictive disorders
-Improves gas exchange, can increase MAP especially on obstructive pts causing airtrapping
Inspiratory Flow/ flow rate
Variable (PRVC), based on resistance (lung dynamics)
Flow rate= 60 lpm (40-60), assure enough flow to meet or exceed pts demand
-Slower flow= longer flow time
Increased Flow
Generates more peak airway pressures
- Gets breath in faster
- Sometimes the faster the flow with higher pressures generates less MAP
- more pressure generated in airways , circuit, and causes uneven ventilation
Lower Flows
Increase WOB, longer I time
- Shortening E time leading to airtrapping
- Goal is too keep flow as slow as possible
- sometimes decrease volumes and increase RR
Asthma death by
Airtrapping, asthma is both obstructive (more) and restrictive
Descending flow
Longer Ti, better gas distribution improving O2, Higher MAP causing more cardiac impairment
-Set PK flow rate on PRVC
Insp. Rise Time
Used to control how fast the pressure rises to Pk, much like flow rate: need to meet or exceed pts demand
Inspiratory Pause (plateau pressure)
Hold breath in lung for a set period of time at the end of a breath. Considered part of the Inspiratory phase (Ti)
- Used to improve gas distribution and improve O2
- Increases MAP causing more cardiac impairments
- PEEP is a better way to improve O2, raises MAP
Inspiratory pause also is used Temporary for determining lung compliance and resistance
Used as a single valve to calculate compliance and resistance set for 0.5 seconds for 3 breaths
Average the number of plateau to record
-remember to turn off if not automatic and it can affect cardiac output
Pressures in chest can decrease BP
Volume Breaths Equation
VT= Ti x Flow
Two have to be set
Factors that affect Ti on flow set breaths
-Vt, flow rate, flow pattern
Set Vt and flow so Ti varies
Ti and how to shorten or lengthen
Vt/ Flow
To shorten= increase flow rate, use square waveform (increases Pk, use when airtrapping), or decrease Vt.
-Decreasing Vt is usually not a good option due to CO2 changes
To lengthen= Decrease flow rate, use ramp waveform
Factors that affect flowrate on Ti set breaths
Vt, Ti
-Vt set and Ti set
Flow=Vt/Ti
To increase flow= shorten Ti, shorten rise time if available
To reduce flow= lengthen Ti, Lengthen rise time if available,
based on Flow = Vt/ Ti what will affect flow rate on PRVC type breaths
Vt and Ti
Phase Variables
Trigger-How breath is started
Cycled- How breath is ended
limited- How the breath is controlled after triggering and before cycling
Baseline- how the breath is controlled during exhalation (PEEP)
Triggering
Time triggered and patient triggered
Time triggered
breath starts when rate control determines, set time between breaths.
-Sometimes called control mode, if a patient is not assisting they are considered in control mode.
Patient Triggered
Pressure triggered, Flow triggered
Pressure triggered
Pt draws a breath creating a negative pressure,ventilator interprets this as an assist and gives the patient a breath (normally set from 0.5 to 2 cmH2O)
Flow triggered
-first choice…
pt draws a breath from a continuous flow creatingless flow in the circuit. The ventilator interprets this as an assist and gives the patient a brea
Limiting (between triggering and cycling)
Pressure limited, volume limited, flow limited
Pressure Limited
during the breath a preset pressure can be reached but not exceeded, the breath will not end until the cycling mechanism is reached. (this is not the same as pressure alarm
-PCV
Volume Limited
during a breath the volume may be limited by the mechanics of the ventilator, this does not end inspiration
Flow limited
a maximum flow is reached and stays at that limit or less but does not cycle the breath off
- Rise Time
- With set flow pattern (flow, descending)
Rise Time
the time it takes the breath to reach peak airway pressure, therefore the flow is adjusted by the vent to assure this is met. This is within the inspiratory time.
-Slow Rise time= Increase PIP, Fast= Air Hungry, go based off pts comfort. Helps synchronize
Cycling (end of exp)
Volume Cycled, Time Cycled, Pressure Cycled, Flow Cycled
Volume cycled
when a volume is reached the breath ends
Time Cycled
-Most common
when a time is reached the breath ends
Pressure Cycled
when a pressure is reached the breath ends
Flow Cycled
when a preset flow is reached the breath ends.
Inspiratory Cycle off
Inspiratory cycle off is a way to adjust the flow rate that ends the breath, this is often a preset/non-adjustable flow on many ventilator
- 25%, hard for pt to get to 0 flow
- Cut off too soon? increase RR
Peak Flow Norm
40-60
Baseline (expiration)
Zero pressure is atmospheric pressure. No added pressure.
Positive end expiratory pressure. Added pressure maintained during expiratory phase. This increases the FRC and is used to improve oxygenation. (raisesbaseline)
Expiratory Hold/ Expiratory retard
Expiratory hold. Place the expiratory phase in the expiratory phase tocheck for autoPEEP. Used only as a test.
Expiratory retard. Mimics pursed lip breathing, slows the flow of air out of the airways preventing airtrapping
Conditional Variables
Changes in types of breaths dependant on data. Such as a sigh being given at a predetermined time or a mandatory breath followed by a spontaneous breath in SIMV
Relationship between flow, volume, and pressure
Pressure control breath, pressure is generated throughout the inspiratory phase. Volume and flow will vary dependent on lung characteristics.
Volume control breath, volume is delivered over a set period of time.
Pressures generated will vary dependent on lung characteristics.
Flow control breath, flow is generated at a steady rate over a set time, this delivers a volume.
Pressures generated will vary dependent on lung characteristic
Types of Breaths
Volume Breaths -Flow limited time cycled -Pressure Regulated Volume Control Pressure Breaths -Pressure limited time cycled -Pressure limited flow cycled Spontaneous
Flow Limited Time Cycled Breaths
Volume breath
- Machine delivers a set amount of flow over a set period of time to create a specific tidal volume. Pressure varies dependant of lung conditions.
- These are the types of breaths on the Star and 7200 when in volume ventilation. These are also the types of breaths on the Servoiin the Volume Control mode, turning off Auto-flow on the Draeger
Pressure Regulated Volume Control
Volume Breaths
- The machine delivers a preset Vt by applying pressure which will adapt to the patient’s condition. The flow pattern and rate will be determined by the patient’s lung conditions.
- These types of breaths are used in the PRVC breathand the Volume support mode on the Servoiand Auto-Flow on the Draeger
Pressure Limited Time Cycled
Pressure Breath
- The machine delivers a preset pressure for a set period of time. The lung conditions will determine flow pattern, flow rate, and volume
- These breaths are pressure control mode
Pressure Limited Flow Cycled
Pressure Breath
- The machine applies a preset pressure to the patient’s lungs during inspiration. The breath will cycle off as the flow decelerates to a predetermined rate.
- The flow pattern, flow rate, inspiratory time, and volume will all be determined by the patient’s lung conditions
- These types of breaths are used in the Pressure Support Ventilation modes and Volume Support Ventilation
How breaths delivered
Full Support
Partial Support
Spontaneous
Automode
Full Support
CMV, AC, PRVC, Vol Control, Press Control
-Mandatory Breaths
Partial Support
SIMV, PSC, Vol Support, BiPAP
-Breathing is supplemented by either assisting the breath or intermittent machine breaths
AutoMode Breaths
Changes modes dependent on the patient’s need for assistance.
Volume Control ↔Volume Support
PRVC ↔Volume Support
Pressure Control ↔Pressure Support
Full Support Modes are used for pts that
Full Support modes are used for patients that cannot breathe on their own or have very little ability to breathe on their own. Seriously ill patients (pneumonia, ARDS), patients that need a rest (COPD/Asthma for 1stday or so), Apneic patients (post-op,neuromuscular disease that cause paralysis, drug induce
Support Modes are for patients that can
Support modes are for patients that can breathe on their own but not adequately enough. Recovering patients (any of above as they get better), neuromuscular diseases (those that cause weakness), moderate respiratory failure (COPD, Asthma )
Spontaneous breathing used on vent to
Spontaneous breathing used on the ventilator to determine if a patient can be extubate
Volume Breaths are for pts that need to
Volume breaths are for patients that need to have assured minute ventilation. Most of our patients are on volume breaths
Pressure Breaths are for patients that need
Pressure breaths are for patients that need to have limited pressure in the lungs. Usually patients with fragile lungs (ARDS, IRDS). There is no assurance of minute ventilation
can be either volume breaths or pressure breath
CMV, AC, SIMV
SIMV can be used as
can be a full support mode if the rate is set high enough to deliver adequate minute ventilation.
PSV can be used to
achieve large tidal volumes
-in some machines PSV is set via the CPAP mode(CPAP mode with PSV set), others CPAP is set via the PSV mode(PSV mode set at zero!
Pressure support that is okay to extubate
6-7, enough to compensate art. airways
If the change in volume remains consistent with varied resistance and compliance, and if the volume is not explicitly measured and used for control, the ventilator is classified as a
Flow Controller
If pressure, volume, and flow are all dependent on system compliance and resistance, the ventilator is designated a
time controller
In pressure control ventilation, a reduction in lung compliance results in increased tidal volume.
T/F
False
-A reduction in lung compliance will result in a reduction in volume, as pressure is independent. In accordance with the equation of motion, if a ventilator is a pressure controller, then pressure is determined by the ventilator settings and is unaffected by changes in compliance and resistance.
what describes pressure control ventilation breaths
Pressure limited time cycled
A mode where everytime a patient initiates a breath a preset volume is given is considered what type of ventilation
CMV
What would increase Expiratory time
increase flow rate
A patient on AC Volume Ventilation is experiencing airtrapping. What changes would reduce it?
decreasing inspiratory time
In PCV if you increase the pk pressures which parameter would also increase
Vt
