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By: Kevin Asp, CRT, RPSGT on August 10th, 2020

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What is AVAPS Mode? (Settings and Indications)

As a sleep physician, sleep technologist, or respiratory therapist, it's important you have comprehensive knowledge of the AVAPS non-invasive ventilation mode so you can hone your skills in using advanced PAP titration technology.

What Is Non-Invasive Ventilation (NIV)?

Noninvasive ventilation (NIV) use has grown over the past couple of decades and has now become an essential tool for managing both chronic and acute respiratory failure in both the critical care unit and the home setting. NIV refers to ventilator support administration without the need to use an invasive artificial airway. 

Sleep physicians use NIV  as an essential complement in patient management of sleep disordered breathing due to its flexibility. 

Rather than using an invasive interface, like tracheostomy or an endotracheal tube, NIV administers positive pressure ventilation through some type of noninvasive interface, such as:

  • Face mask
  • Nasal mask
  • Nasal pillows

How Does Non-Invasive Ventilation Work?

NIV delivers breathing support through a noninvasive technique, such as a nasal mask rather than a tracheostomy or other invasive approach. The NIV machine assists to:

  • Inflate the lungs fully
  • Reduce carbon dioxide levels
  • Improve blood oxygen levels

NIV can also work by enhancing your patients' sleep quality and ease symptoms such as

  • Daytime fatigue
  • Morning headaches
  • Shortness of breath

that might be due to accumulated carbon dioxide, low levels of oxygen, and/or sleep fragmentation.

What Is the Benefit of Non-Invasive Ventilation?

NIV therapy decreases the work patients with chronic respiratory failure have to put in to breathe. 

Some benefits of noninvasive ventilation compared to invasive ventilation are:

  • More convenient
  • Reduced cost
  • The ability to interrupt therapy for breaks allowing for simpler weaning from mechanical support
  • Greater availability outside the ICU setting (i.e. home)
  • Doesn't require airway skills to begin therapy
  • Tolerated better (doesn't require sedation)

What Is AVAPS?

AVAPS is average volume-assured pressure support. It is a noninvasive technology developed to ensure delivery of a fixed tidal volume; how much air is moving in or out of the lungs with every respiratory cycle, along with the benefits and convenience of pressure support ventilation. 

AVAPS is designed specifically for taking over the control of and adapting automatically to each patient's changing therapy needs. It is a noninvasive home ventilator that provides your patient with the accurate pressure volume required to maintain adequate treatment.

What Does AVAPS Rate Mean?

With the AVAPS rate setting, you are able to adjust the pressure support maximum rate at which the device automatically changes in order to achieve the target tidal volume. The AVAPS algorithm changes pressure support quicker at a higher rate to meet the target tidal volume. You can set this in 1 cm H2O per minute increments ranging from 1 to 5 cm H2O per minute.

What are the Indications for AVAPS?

There are various AVAPS indications, including:

  • It provides patients who have chronic respiratory insufficiency with noninvasive ventilation, and using EPAP treats Obstructive Sleep Apnea (OSA) in the AE mode. It also helps many chronic respiratory failure patients requiring ventilator support.
  • It is usually used in chronic hypoventilation patients, like those with neuromuscular diseases, Obesity Hypoventilation Syndrome (OHS), restrictive thoracic disorders, and Chronic Obstructive Pulmonary Disease (COPD).
  • It revolutionizes how Bi-Level therapy is provided to patients with breathing complications. The AVAPS device delivers a constant tidal volume of pressure to patients and uses a specific algorithm that automatically calculates the pressure changes needed to maintain an optimal tidal volume.

What Are the Benefits of AVAPS?

There are various benefits of AVAPS, including:

  • It can help many patients maintain their tidal volume.
  • It can assist patients with respiratory insufficiency because of restrictive and neuromuscular disorders where the respiratory effort will vary while they sleep.
  • It can help COPD patients at risk for hypoventilation.
  • It can help patients requiring non-invasive positive pressure ventilation (NiPPV) throughout the day.
  • It can help obesity hypoventilation (OHS) patients who might require compensation based on sleep stage and/or position changes.

Since during the rapid eye movement (REM) cycle of sleep, patients can have far worse hypoventilation, BiPAP with fixed pressure support (PS) might provide too much pressure in NREM sleep, leading to complex sleep apnea or intolerance, and might not give enough PS in REM sleep for controlling carbon dioxide (PaCO2) levels.

When Should AVAPS Not Be Used?

Patients should not use AVAPS if they require rapid inspiratory pressure (IPAP) adjustments for achieving the desired tidal volume. This means you should not see a change of over 2.5 cmH2O within a minute. Therefore, you should not use it for all patients.

What are the Settings Used for AVAPS? 

The target tidal volume, depending on patient pathology can be set to 8ml/kg of the ideal weight.

  • The maximum IPAP equals 25 to 50 cmH2O which depends on the condition of the patient and the machine's available pressure.
  • The minimum IPAP equals EPAP + 4 cmH20 which depends on the patient's condition.

AVAPS Settings IPAP Limits and Tidal Volume

Watch the video below taken from the Advanced Sleep Titration e-Learning Course

Click the button to learn more about the Advanced Sleep Titration e-Learning Course

AAST Advanced Sleep Titration e-Learning Course


How Does the IPAP Know Which Initial IPAP to Set or Pressure to Begin the First Breath?

AVAPS contains a startup algorithm that automatically selects a higher value. Since higher pressures aren't tolerated well, the maximal pressure (max P) is usually set in a 20 to 25 cm water range. The minimum pressure (min P) is a minimum of 8 cm water and typically higher. The AVAPS settings also have additional parameters that include:

  • Respiratory rate
  • Target tidal volume
  • Inspiratory time
  • EPAP

AVAPS maintains a tidal volume that's higher or equal to the targeted tidal volume through pressure support changes made with each breath that are between the minimum and maximum IPAP settings. 

Pressure support can be adjusted by your patient's efforts too breathe, as it averages tidal volume over a window of a few minutes. If your patient's effort is reduced, AVAPS will increase the tidal volume. If your patient's effort increases, the device will decrease the pressure delivered. If the targeted tidal volume in AVAPS isn't reached, the ventilator function will take over in order to provide the needed pressure support for reaching the goal.

What Studies Have Been Done on AVAPS? 

Various studies have been conducted for AVAPS. 

1. One study was done to investigate ST/AVAPS mode benefits in delivering NIV to patients with AHRF in comparison with standard ST/BiPAP mode. The patients in the study were randomized to receive NIV and were placed in two groups: 

  • Group 1: 30 patients using BiPAP-ST mode
  • Group 2: 30 patients using BiPAP ST/AVAPS

At one hour, substantial improvement in PaO2 was observed in both groups. At 12 hours, substantial improvement in RR, GCS, and PH was seen in group 2 as well as a sustained improvement in SaO2 and PaO2.

At 48 hours, substantial improvement was seen in PaCO2 with the other parameters maintaining improvement. But, group 1 only showed substantial improvement in RR at 12 hours with further substantial improvement in other clinical parameters at 48 hours. And, the duration spent on NIV was substantially less in group 2 than it was in group 1.

2. In another study, AVAPS vs BiPAP was compared. There were 33 patients over 18 years old in the study who had an acute respiratory failure due to either surgical or internal reasons. The Philips V 60 ventilator was used in the study and includes both AVAPS and BiPAP mode.

When researchers evaluated patients according to their BMI (body mass index), the patients' with BMI ≥30 had pCO2 and pH values showing better improvement using AVAPS in all three measurements than with BiPAP. When the researchers examined the patients' compliance, there were 66.7% (20 patients) seen as being comfortable with BiPAP and 83.3% (25 patients) for AVAPS.

Using AVAPS, the patient's need for sedation was lower and their comfort was higher. The study's results showed AVAPS had a positive impact on pH, patient comfort, and gas variation so it could be used confidently in clinical practice.

Take Advantage of Advanced Sleep Titration e-Learning Course 

AAST, the community for sleep-care professionals, is introducing our brand new online Advanced Sleep Titration e-Learning Course committed to state-of-the-art titration techniques and technology. This course consists of five modules that build on each other and results in you obtaining a comprehensive understanding of cardiorespiratory anatomy and physiology as well as enhancing your skills in Positive Airway Pressure (PAP) titration at basic and advanced levels.

Course topics include:

  • CPAP and BPAP Titration Guidelines
  • Noninvasive Positive Pressure Ventilation (NPPV and AVAPS)
  • Physiology and Anatomy
  • Average Volume Assured Pressure Support Auto EPAP (AVAPS-AE)
  • Adaptive Servo Ventilation (ASV)

All modules also come with a knowledge check section and glossary for validating important learning objectives. You also have access to three interactive titration scenarios, which will allow you to apply course lessons and practice new titration skills.

To track your CECs in your Continuing Education Transcript, be sure to log in to your AAST Member account before making your Advanced Sleep Titration Course purchase.  For more information and/or to enroll in the Advanced Sleep Titration e-Learning Course, visit here.


AAST Advanced Sleep Titration e-Learning Course




About Kevin Asp, CRT, RPSGT

Because of the implementation of his best practices of Implementing Inbound Marketing in its Medical Practice, he turned the once stagnant online presence of Alaska Sleep Clinic to that of "The Most Trafficked Sleep Center Website in the World" in just 18 months time. He is the President and CEO of inboundMed and enjoys helping sleep centers across the globe grow their business through his unique vision and experience of over 27 years in sleep medicine.

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