Chapter 3 - How a Breath is Delivered Flashcards
What are the Two types of pressures?
Muscle and Ventilation
What characteristics is volume dependent on?
Compliance and Resistance
What does Pressure, Volume, and Flow equate to?
The Equation of Motion
What is the starting point where the breath begins?
Baseline
What are the two types of Triggers?
Time and Patient
How is Patient Trigger “Triggered”?
Flow, Pressure, Volume
How is Time Trigger “Triggered”?
Vent delivers breath at set intervals
What is Trigger Dyssynchrony?
When a pt wants to trigger a breath, but cannot
What is Flow Dyssynchrony?
When a pt wants to get a breath of 40 LPM, but the vent is set at 30 LPM
What percentage of Intrinsic Peep do we set Extrinsic Peep?
Either on a CPAP or other vent modes
We set Extrinsic Peep to 80% of Intrinsic Peep
Which is about 4-10 cm H20
Which is more sensitive, Flow or Pressure Triggering?
Flow
What ventliator has Volume Triggering?
Babylog
What terminates a breath?
Cycling
What are two examples of pressure limiting modes?
Pressure ventilation & Pressure Support
What does Pressure Limiting modes do?
- Allows pressure to rise to a preset level
- Vents excess pressure from the circuit
- Used frequently with infant ventilators
Volume Cycled Ventilation
- Breath is terminated when the set vol is delivered
- In most cases the vol is not affected by changes in lung characteristics
- If an inspiratory puase is used the ventilator is considered volume limited but time cycled
Time Cycled Ventilation
- If the breath terminates at a preset interval
- The vol is not affected by changes in lung characteristics
- If used with a fixed time interval, Vt=Flow x IT
Time Cycled - Pressure Ventilation
- Vol and Flow are variable
- Most common is Pressure Control Ventilation (PCV)
What are the 3 types of breaths?
- Mandatory
- Assisted (PS)
- Spontaneous (CPAP)
What occurs when PC I-time is set long enought for flow to hit zero?
PIP and Plat will be the same
Can Pip and Plat be the same in VC?
No, as there is still flow at the end that includes resistance
How can you ensure Pip and Plat are equal in PC?
Lengthen the I-time
What setting sets two peep levels?
APRV
What is Time Limited Exhalation?
Allows I-time and E-time to be set
What does an expiratory Hold do?
- Measures Auto-Peep or Air Trapping
- Creates back pressure and allows it to equalize
What is Refractory Hypoxemia?
-Mean that the tx isn’t making it any better
What is intrinsic PEEP?
Auto-PEEP. incomplete exhalation that can lead to hyperinflation and Air trapping.
What is Extrinsic PEEP?
Applied PEEP from ventilator.
What are the 4 variables that are controlled by the Ventilator?
Pressure
Volume
Flow
Time
What are the 2 options that the operator can choose for the delivery of a breath?
Pressure
Volume
In pressure controlled breathing, What is not affected by lung characteristics and what is affected?
Pressure is not affected, but flow and volume are.
In flow controlled breathing, What is not affected by lung characteristics and what is affected?
Flow and volume are not affected, but pressure is affected
Where do you see time controlled breathing?
High frequency and oscillator Vents
What are the 3 graphics observed in a vent and where are they measured?
Pressure - Measured at airway opening
Volume - at the EXP valve
Flow - measured at outlet of vent
What are the 4 phase of a breath/variables?
Trigger Variable
Limit Variable
Cycle Variable
Baseline Variable
What is a Trigger Variable? What are the types of trigger variables?
This the the setting that an operator inputs to so that the patient can start a breath
Ventilator Trigger
Patient Trigger
Operator Trigger
Time Trigger
What does it mean if we say the patient is in a control mode?
The patient is triggering any breaths on their own.
The machine is initiating everything.
What are the ways that the PATIENT can trigger the breath?
pressure
flow
volume
What is the Limit Variable?
It is a setting that you input to signal when the breath should end.
What is the difference between a safety and a limit variable?
A safety variable will terminate the breath if it is reached , where are a limit variable will end the breath.
Which vent mode best compensates for leaks?
Why?
Pressure control. because it can compensate for loss of volume by adding more flow.
in volume ventilation, volume is calculated by flow exiting from vent. when it reaches it target volume from the inspiratory valve, it cycles off.
What is flow cycling?
After the vent has reached its PIP and flow is tapering off, Flow will be cut at at preset or determined point and start exhalation.
Which is usually 25% of PIP
What is the baseline variable for?
It is the level at which the breath begins.
PEEP and ZEEP.
It can also be set for Time or flow as well.
What occurs in the circuit during exhalation with regards to flow?
There is a baseline/bias flow that is continuously flowing through the circuit. Its the Basis for Flow Trigger
It helps in reducing resistance during exhalation and allows immediate flow during spontaneous inhalation.
SOME vents can also have Neg Pressure to also ease exhalation.
What is bias flow used for?
It is the basis for flow triggering,
It helps with exhalation
It is used to maintain PEEP levels
