Airway Pressure Release Ventilation

Summary

In this video, the presenter explains Airway Pressure Release Ventilation (APRV), a less commonly used but beneficial ventilator setting. APRV is designed to maintain lung pressure, preventing alveolar collapse and aiding in oxygenation. Key settings, such as P high, P low, T high, and T low, are discussed, along with the concept of 'drop and stretch' for weaning. While typically used for ARDS patients, APRV has not been proven to improve morbidity or mortality, although it may reduce ICU and ventilator days. The video aims to clarify APRV and help viewers understand its settings and purpose in critical care.

Takeaways

• 😀 APRV (Airway Pressure Release Ventilation) is a unique ventilation technique with benefits not seen in traditional methods.
• 😀 Unlike common ventilator settings, APRV requires the adjustment of P high, P low, T high, and T low.
• 😀 P high (pressure high) is the pressure delivered to the patient during inspiration, and T high is the time spent at P high.
• 😀 P low (pressure low) is the pressure delivered during expiration, and T low is the time spent at P low.
• 😀 The APRV mode operates similarly to BiPAP, where the machine delivers higher pressure during inspiration and lower pressure during expiration.
• 😀 The goal of APRV is to prevent alveolar collapse, thus improving oxygenation by maintaining lung recruitment.
• 😀 APRV also aims to prevent atelectasis (collapse of alveoli), which can form shunts and impair gas exchange.
• 😀 During APRV, the patient can breathe spontaneously, both during high pressure and during the low pressure phase, leading to some oscillation in pressure.
• 😀 Key settings for APRV include a P high of no more than 30 cm H2O and a P low of 0 to 5 cm H2O, with T high ranging from 10 to 16 seconds.
• 😀 The weaning strategy in APRV involves a gradual decrease in P high and an increase in T high (referred to as 'drop and stretch') to transition the patient to a CPAP-like state.
• 😀 While APRV is commonly used for ARDS, there is no conclusive evidence that it improves morbidity or mortality, though it may reduce ventilator days and ICU stays.

Q & A

What is Airway Pressure Release Ventilation (APRV)?

APRV is a type of mechanical ventilation used to help manage patients with respiratory conditions, such as ARDS. It delivers two pressure levels, P high and P low, and alternates between these pressures for set periods of time (T high and T low), to prevent alveolar collapse and improve oxygenation.

How does APRV compare to BiPAP in terms of pressure settings?

APRV works similarly to BiPAP in that it delivers higher pressure during inspiration (P high) and lower pressure during expiration (P low). However, unlike BiPAP, APRV alternates between these pressures over time with a set time for each pressure level (T high and T low).

What is the primary goal of APRV?

The primary goal of APRV is to prevent alveolar collapse by maintaining a higher pressure in the lungs for a majority of the time, thus improving lung recruitment and oxygenation while minimizing atelectasis.

What are the typical settings for P high and P low in APRV?

P high is typically set between 20 to 30 cmH2O, with 25 cmH2O being a common target. P low can be set at 0 or slightly above 0, usually up to 5 cmH2O, depending on the desired lung mechanics and avoidance of collapse.

Why might P low be set to a value greater than zero?

Setting P low greater than zero helps prevent alveolar collapse by maintaining some positive pressure in the lungs during expiration. This creates a smaller pressure gradient between P high and P low, but it can make exhalation harder and may contribute to hypercapnia.

What is the typical duration for T high and T low?

T high is typically set between 10 to 16 seconds, while T low is usually between 0.5 and 0.6 seconds. The ratio of T high to T low should ensure that the patient spends at least 90% of the time at P high.

What does 'drop and stretch' mean in the context of APRV weaning?

'Drop and stretch' refers to the gradual weaning process in APRV, where P high is progressively decreased and T high is increased. This approach aims to reduce the pressure required to keep the alveoli open, transitioning the patient toward CPAP settings.

Is APRV commonly used in clinical practice?

APRV is not the most commonly used ventilation technique, but it may be beneficial in certain cases, especially for ARDS patients. It is a specialized mode that requires specific settings and monitoring.

What impact has APRV been shown to have on ventilator and ICU days?

Studies suggest that APRV may lead to a reduction in ventilator days and ICU stays. However, it does not appear to have any effect on overall morbidity or mortality in patients.

How does APRV affect tidal volume?

Tidal volume in APRV is influenced by the patient’s spontaneous breathing. The patient breathes over the pressure waves created by the ventilator, with tidal volume varying depending on whether the patient is in the P high or P low phase.