APRV stuff

Question 1

Initial Settings for APRV?

Answer 1

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)

Question 2

What do you need to ensure is adjusted after setting initial settings?

Answer 2

Adjust end expiratory flow to 75% of PEFR

Question 3

What are you goals for Phigh?

Answer 3

Ensure a ratio of 4:1 or greater; want 90-95% of time spent at Phigh

Question 4

Add slide 19 (APRV vent quirks)

Answer 4

Question 5

What are other names for APRV?

Answer 5

Bivent or Bilevel

Question 6

How do you adjust APRV settings to increase ventilation?

Answer 6

1. Increase Phigh or decrease Thigh
2. Increase or decrease Tlow

Question 7

How do you adjust APRV settings to increase oxygenation?

Answer 7

Increase Phigh or Thigh

• Decrease Tlow

Question 8

Weaning APRV?

Answer 8

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

Question 9

Contraindications for APRV?

Answer 9

Air leak syndromes and condition of TBI/high ICP

Question 10

What is Phigh?

Answer 10

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

Question 11

What is Plow?

Answer 11

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.

Question 12

What is Thigh?

Answer 12

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.

Question 13

What is Tlow?

Answer 13

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

Question 14

In Airway Pressure Release Ventilation (APRV), the settings that primarily affect the I:E (inspiratory to expiratory) ratio and respiratory rate include?

Answer 14

Primarily Thigh and Tlow; RR is also connected and could be manipulated

Question 15

How does Thigh affect the I:E ratio?

Answer 15

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.

Question 16

How does Tlow affect the I:E ratio?

Answer 16

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.

Question 17

How could Phigh increase Oxygenation?

Answer 17

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.

Question 18

Why is Tlow optimization important?

Answer 18

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

Question 19

What change in APRV would best address v/q mismatch or atelectasis?

Answer 19

Prolonging Thigh; Lengthening Thigh allows for a longer duration of time at the high CPAP level, facilitating better recruitment of alveoli and improving oxygenation.

Question 20

How does Tlow affect respiratory rate?

Answer 20

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

Question 21

How does Tlow affect the expiratory phase?

Answer 21

1. Increased Tlow makes the expiratory phase longer; increasing TCT
2. Decreased Tlow shortens the expiratory phase while the inspiratory phase (Thigh) remains constant; Shortening E time reduces TCT

Question 22

How does increasing Phigh affect ventilation?

Answer 22

Increase Phigh = Increase Vt = increase oxygenation

Question 22

What does decreasing Thigh to ventialtion?

Answer 22

Decrease Thigh = Increasing RR and decreasing MAP which should decrease oxygenation

Question 23

Increase Thigh does what to Ventilation

Answer 23

Decreases RR = lowers ventilation

Question 24

Decrease Thigh does what to Ventilation

Answer 24

Increases RR and improves ventilation

Question 25

Decrease Phigh does what to Ventilation

Answer 25

Decreases Vt - Decreases ventialtion and oxygenation

Question 26

Increase Phigh does what to ventilation

Answer 26

Increases Vt - improves ventilation and oxygenation