Average Volume Assured Pressure Support (AVAPS) vs Conventional Bi-level Pressure Support (BiPAP): Key Differences and Benefits

By Terrence Shenfield MS, RRT-ACCS, RPFT, NPS, AE-C  ·  Published April 2025  ·  Updated March 2026

Advancements in respiratory therapy technology have revolutionized patient care, providing clinicians with diverse tools to manage respiratory insufficiency. Among these innovations, Average Volume Assured Pressure Support (AVAPS) and Conventional Bi-level Positive Airway Pressure (BiPAP) stand out as leading methods of noninvasive ventilation (NIV). While both ensure effective gas exchange and enhanced oxygenation, their mechanisms and applications differ significantly.

This article explores what AVAPS is in respiratory therapy, the best clinical uses for both BiPAP and AVAPS, how to set initial AVAPS parameters, and a direct comparison to help clinicians make informed ventilation decisions.

AVAPS vs BiPAP: Quick Reference Comparison

Use this table for a fast side-by-side overview. Detailed explanations follow in each section below.

Feature	BiPAP	AVAPS
Pressure mode	Fixed IPAP & EPAP	Dynamic IPAP — auto-adjusts
Tidal volume guarantee	No	Yes — clinician sets target
Best for acute conditions	Yes — first-line choice	Less common acutely
Best for chronic conditions	Yes (COPD, OSA)	Yes (OHS, NMD, central apnea)
Obesity hypoventilation (OHS)	Sometimes used	Preferred treatment
Neuromuscular disorders	Used	Preferred — ensures volume
Patient comfort (long-term)	Good	Better — smoother transitions
Setup complexity	Simple	Moderate — requires titration
Real-time data monitoring	Basic	Advanced — breath-by-breath
Manual adjustment frequency	Higher	Lower — self-adjusting
Device cost	Lower	Higher
Insurance coverage	Widely covered	Covered for qualifying diagnoses

What is Bi-level Positive Airway Pressure (BiPAP)?

BiPAP is a widely used noninvasive ventilation (NIV) mode designed to treat respiratory insufficiency in conditions like chronic obstructive pulmonary disease (COPD), obstructive sleep apnea (OSA), and acute respiratory failure. This modality delivers two levels of airway pressure:

• Inspiratory Positive Airway Pressure (IPAP): A higher pressure during inhalation to assist ventilation and reduce the work of breathing.
• Expiratory Positive Airway Pressure (EPAP): A lower pressure during exhalation to keep the airways open and improve oxygenation.

Key Features of BiPAP

• Fixed Pressure Settings: IPAP and EPAP levels are manually adjusted to meet the patient's ventilation needs.
• Non-Guaranteed Tidal Volume: BiPAP focuses on maintaining consistent pressure rather than delivering a fixed volume of air.
• Ideal for Acute and Chronic Conditions: Effective for short-term acute failures and chronic diseases requiring regular support.

Best Uses for BiPAP

• Obstructive Sleep Apnea (OSA): Reduces airway resistance and prevents apneas during sleep.
• COPD Exacerbations: Reduces elevated carbon dioxide (hypercapnia) and eases the respiratory workload.
• Acute Respiratory Failure: Stabilizes patients in emergency settings with immediate pressure support.

Learn more about BiPAP applications on our Mechanical Ventilation page.

What is AVAPS in Respiratory Therapy?

Average Volume Assured Pressure Support (AVAPS) builds upon the BiPAP framework by ensuring a target tidal volume is delivered to patients. This dynamic adjustment in inspiratory pressure makes AVAPS suitable for patients with fluctuating respiratory needs, such as those with neuromuscular disorders or obesity hypoventilation syndrome (OHS).

How AVAPS Works

1. Target Tidal Volume: The clinician sets a desired tidal volume, and the ventilator adjusts IPAP dynamically to achieve it.
2. Adaptive Pressure Support: Pressure support changes within a defined range to maintain consistent ventilation as patient needs fluctuate.
3. Hybrid Mode: Combines volume control with the comfort of noninvasive ventilation, making it ideal for progressive or complex conditions.

Key Features of AVAPS:

1. Volume Guarantee: Ensures consistent tidal volume even during changing lung mechanics or respiratory demands.
2. Safe Pressure Adjustments: Adjusts IPAP within preset limits, ensuring patient safety and comfort.
3. Advanced Monitoring: Tracks real-time respiratory data to enhance clinical decision-making.

Best Uses for AVAPS

• Obesity Hypoventilation Syndrome (OHS): Delivers stable ventilation despite reduced lung compliance in OHS.
• Neuromuscular Disorders: Ideal for progressive diseases like ALS or muscular dystrophy, where respiratory needs evolve over time.
• Complex Hypoventilation: Helps manage irregular or unstable breathing patterns by maintaining steady tidal volumes.

To see AVAPS in action, watch our comprehensive YouTube lecture here.

How to Set Up AVAPS: Initial Settings Guide

One of the most common clinical questions is how to initiate AVAPS settings for a new patient. While settings should always be individualized based on patient assessment, the following parameters are commonly used as starting points in clinical practice.

Recommended AVAPS Starting Parameters:

• Target tidal volume: 8–10 mL/kg ideal body weight (IBW)
• IPAP minimum (IPAPmin): 8–10 cmH₂O
• IPAP maximum (IPAPmax): 20–25 cmH₂O
• EPAP: 4–6 cmH₂O (increase for OSA/upper airway obstruction)
• Backup respiratory rate: 10–14 breaths/min (or match patient's spontaneous rate)
• Rise time: 1–3 (shorter for COPD/active patients; longer for comfort)

⚠️ Always titrate AVAPS in a monitored setting, particularly for new patients or those with significant hypercapnia. Re-evaluate after the first night of use with a device data download review.

AVAPS-AE vs Standard AVAPS

AVAPS-AE (Auto EPAP) automatically adjusts both IPAP and EPAP to maintain target tidal volume while simultaneously managing upper airway obstruction. Standard AVAPS uses a fixed EPAP setting. AVAPS-AE is particularly useful for patients with combined obstructive and hypoventilation issues — for example, a patient with both OSA and OHS.

? Clinical tip: For OHS patients with suspected OSA, consider AVAPS-AE as first-line to address both obstruction and hypoventilation in a single device setting. Review the first-night compliance download to confirm adequate tidal volumes are being met throughout the night.

Comparing AVAPS and Conventional BiPAP

Both AVAPS and BiPAP play a pivotal role in noninvasive ventilation but differ significantly in operation, adaptability, and the conditions they treat best.

1. Pressure Adjustments

• BiPAP delivers fixed IPAP and EPAP levels, which require manual adjustments for changes in patient condition.
• AVAPS dynamically alters inspiratory pressure breath-by-breath to ensure the target tidal volume is consistently met.

2. Tidal Volume Control

• BiPAP does not guarantee tidal volume, which can result in insufficient ventilation if patient lung mechanics fluctuate.
• AVAPS ensures tidal volume control, making it superior for addressing progressive hypoventilation.

3. Monitoring and Data Analysis

• BiPAP offers basic parameter monitoring such as respiratory rate and pressure levels.
• AVAPS provides real-time, data-driven insights — including breath-by-breath tidal volume tracking — empowering clinicians to make precise therapy adjustments.

4. Patient Comfort and Long-Term Compliance

• BiPAP is effective for short-term or stable respiratory issues, but fixed pressures can feel less comfortable over time.
• AVAPS minimizes abrupt pressure changes and ensures smoother transitions, leading to higher patient compliance in long-term therapy.

AVAPS Advantages Over BiPAP

1. Adaptive Ventilation: Automatically adjusts to meet respiratory needs, offering targeted and individualized therapy.
2. Reduced Manual Intervention: With self-adjusting pressure support, AVAPS eliminates the need for frequent adjustments, saving time and resources.
3. Improved Ventilation Outcomes: Greater consistency in tidal volume promotes better oxygenation and CO₂ elimination.
4. Enhanced Long-Term Comfort: Smooth pressure transitions make AVAPS more suitable for patients needing long-term ventilatory support.

For an in-depth comparison, visit our Mechanical Ventilation course category.

Clinical Applications: When to Choose BiPAP vs AVAPS

Here is a quick-reference guide for selecting the right ventilation mode based on clinical scenario:

Clinical Scenario	Recommended Mode	Rationale
Acute respiratory failure	BiPAP	Rapid setup; well-established protocol
COPD exacerbation	BiPAP	Reduces hypercapnia; first-line NIV
Obstructive sleep apnea (OSA)	BiPAP	Fixed pressure adequate for obstruction
Neuromuscular disease (ALS, MD)	AVAPS	Guarantees volume as disease progresses
Obesity hypoventilation syndrome	AVAPS	Preferred — manages variable compliance
Central sleep apnea	AVAPS	Backup rate + volume guarantee
OSA + OHS (combined)	AVAPS-AE	Auto-EPAP addresses both conditions
Complex hypoventilation	AVAPS	Maintains steady tidal volume
Diaphragm paralysis	AVAPS	Ensures adequate minute ventilation

Key Clinical Takeaway: If your patient's primary problem is obstruction (OSA, COPD exacerbation) → start with BiPAP. If the primary problem is hypoventilation with evolving or unstable lung mechanics (OHS, NMD, progressive disease) → AVAPS is the preferred choice.

Limitations of AVAPS

Despite its many advantages, AVAPS presents some clinical challenges to be aware of:

1. Slower Pressure Adjustments: Adaptation happens gradually (breath-to-breath over minutes), making it unsuitable for emergencies requiring rapid ventilation changes.
2. Higher Cost: AVAPS devices are typically more expensive than standard BiPAP, limiting accessibility in some healthcare settings.
3. Complex Setup: Proper AVAPS configuration requires trained clinicians — it is not recommended for non-specialists without adequate training.
4. Patient Adjustment Period: Some patients find the varying pressure uncomfortable initially. Most adapt within 1–4 weeks with proper education and gradual titration.

Frequently Asked Questions: AVAPS vs BiPAP

Is AVAPS better than BiPAP?

AVAPS is not universally better — it depends on the patient's condition. AVAPS is preferred for obesity hypoventilation syndrome (OHS), neuromuscular disorders, and conditions where consistent tidal volume delivery is critical. BiPAP remains the standard for COPD exacerbations and straightforward OSA where fixed pressure support is effective.

What is the difference between AVAPS and BiPAP?

BiPAP delivers fixed IPAP and EPAP pressure settings set by the clinician. AVAPS dynamically adjusts inspiratory pressure to guarantee a clinician-set target tidal volume, adapting breath-by-breath as the patient's lung mechanics change. BiPAP maintains pressure; AVAPS maintains volume.

What are the starting settings for AVAPS?

Typical starting parameters: target tidal volume 8–10 mL/kg IBW; IPAPmin 8–10 cmH₂O; IPAPmax 20–25 cmH₂O; EPAP 4–6 cmH₂O; backup rate 10–14 breaths/min. Always titrate in a monitored clinical setting and review device data after the first night.

What is AVAPS-AE and how does it differ from standard AVAPS?

AVAPS-AE (Auto EPAP) automatically adjusts both IPAP and EPAP to maintain target tidal volume while also managing upper airway obstruction. Standard AVAPS uses a fixed EPAP. AVAPS-AE is ideal for patients with both obstructive sleep apnea and hypoventilation (such as OHS + OSA).

Can AVAPS replace BiPAP?

In many chronic hypoventilation conditions, AVAPS can replace BiPAP and often provides superior outcomes by guaranteeing target ventilation. However, BiPAP remains appropriate — and often preferred — for acute conditions and many chronic respiratory diseases where fixed-pressure therapy is effective.

What conditions is AVAPS approved for?

AVAPS is indicated for conditions causing chronic hypoventilation, including obesity hypoventilation syndrome (OHS), neuromuscular diseases (ALS, muscular dystrophy, diaphragm paralysis), central sleep apnea, and COPD with hypercapnia (elevated CO₂).

Advancing Respiratory Therapy with AVAPS and BiPAP

Technological advancements in respiratory therapy, such as AVAPS, push the boundaries of what noninvasive ventilation can achieve. From better compliance and adaptability to improved clinical outcomes, AVAPS sets a new standard for treating progressive and complex respiratory conditions.

While BiPAP remains a valuable tool for managing short-term and stable respiratory insufficiencies, the advantages AVAPS offers make it indispensable for conditions marked by evolving breathing needs. With targeted therapies and minimized manual intervention, AVAPS is likely to see broader adoption in the years to come.

Curious to learn how to integrate these advanced modes into your clinical practice? Explore our PDF and video resources here.