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