APRV stuff Flashcards
Initial Settings for APRV?
When transferring form conventional ventilation:
- Phigh match Plat on current mode (max 30)
- Plow set to 0
- Thigh 4
- T low 0.5-1 (often 0.8)
What do you need to ensure is adjusted after setting initial settings?
Adjust end expiratory flow to 75% of PEFR
What are you goals for Phigh?
Ensure a ratio of 4:1 or greater; want 90-95% of time spent at Phigh
Add slide 19 (APRV vent quirks)
What are other names for APRV?
Bivent or Bilevel
How do you adjust APRV settings to increase ventilation?
- Increase Phigh or decrease Thigh
- Increase or decrease Tlow
How do you adjust APRV settings to increase oxygenation?
Increase Phigh or Thigh
- Decrease Tlow
Weaning APRV?
Achieved by: decreasing Phigh then increasing Thigh
- The goal is to wean the patient to a low level of CPAP
- Decreasing Thigh decreases RR which allows the patient to breath
Contraindications for APRV?
Air leak syndromes and condition of TBI/high ICP
What is Phigh?
Phigh represents the high continuous positive airway pressure (CPAP) level during the inspiratory phase of the ventilator cycle.
- Determines the level of positive pressure applied to the airways to recruit and maintain alveolar inflation
- Set above baseline PEEP to support lung recruitment and oxygenation
What is Plow?
Plow represents the low CPAP level during the expiratory phase of the ventilator cycle.
- Determines the level of positive pressure maintained in the airways during the expiratory phase to prevent alveolar collapse and maintain functional residual capacity (FRC)
- Plow is usually set below Phigh to allow for passive expiration and CO2 elimination.
What is Thigh?
High pressure time; duration of time which the vent maintains Phigh (High CPAP pressure) in the inspiratory phase.
- Determines the duration of time allocated for lung recruitment and oxygenation.
What is Tlow?
Low pressure time; duration of time during which the ventilator maintains the Plow level (low CPAP pressure) in the expiratory phase
- Determines time allowed for passive expiration and CO2 elimination
- Prevents air trapping
In Airway Pressure Release Ventilation (APRV), the settings that primarily affect the I:E (inspiratory to expiratory) ratio and respiratory rate include?
Primarily Thigh and Tlow; RR is also connected and could be manipulated
How does Thigh affect the I:E ratio?
Thigh determines the duration of time during which the ventilator maintains the Phigh (high CPAP pressure) level in the inspiratory phase.
- Increasing Thigh will prolong the inspiratory phase, thereby increasing the I:E ratio and potentially decreasing the respiratory rate.
How does Tlow affect the I:E ratio?
Tlow determines the duration of time during which the ventilator maintains the Plow (low CPAP pressure) level in the expiratory phase.
- Decreasing Tlow will shorten the expiratory phase, potentially increasing the I:E ratio and respiratory rate.
How could Phigh increase Oxygenation?
Raising the Phigh level increases the mean airway pressure, which can enhance alveolar recruitment and improve oxygenation. However, it’s essential to monitor for signs of overdistension and adjust Phigh cautiously.
Why is Tlow optimization important?
Ensuring an adequate Tlow allows sufficient time for passive expiration and CO2 elimination.
- Shortening Tlow may improve CO2 clearance and prevent air trapping, leading to enhanced ventilation
What change in APRV would best address v/q mismatch or atelectasis?
Prolonging Thigh; Lengthening Thigh allows for a longer duration of time at the high CPAP level, facilitating better recruitment of alveoli and improving oxygenation.
How does Tlow affect respiratory rate?
Increasing Tlow in APRV could decrease RR and lower PaCO2
- recall; it affects the I:E ratio more bc Tlow affects the expiratory phase
- TCT increases bc of prolonged exp time
How does Tlow affect the expiratory phase?
- Increased Tlow makes the expiratory phase longer; increasing TCT
- Decreased Tlow shortens the expiratory phase while the inspiratory phase (Thigh) remains constant; Shortening E time reduces TCT
How does increasing Phigh affect ventilation?
Increase Phigh = Increase Vt = increase oxygenation
What does decreasing Thigh to ventialtion?
Decrease Thigh = Increasing RR and decreasing MAP which should decrease oxygenation
Increase Thigh does what to Ventilation
Decreases RR = lowers ventilation
Decrease Thigh does what to Ventilation
Increases RR and improves ventilation
Decrease Phigh does what to Ventilation
Decreases Vt
- Decreases ventialtion and oxygenation
Increase Phigh does what to ventilation
Increases Vt
- improves ventilation and oxygenation
