What is Average Volume-Assured Pressure Support (AVAPS)?

From the Guidelines

AVAPS is a recommended mode of noninvasive positive pressure ventilation (NPPV) for patients with stable chronic alveolar hypoventilation syndromes, as it automatically adjusts the IPAP to deliver a targeted tidal volume. When using AVAPS, the goals of NPPV titration are to select an effective EPAP to eliminate obstructive events and to document that the device delivers adequate pressure support 1. The recommended initial settings for volume targeted pressure support include EPAP = 4 cm H2O, IPAP min = EPAP + 4 cm H2O, and IPAP max = 25 to 30 cm H2O, with an initial target tidal volume setting of approximately 8 mL/kg ideal body weight 1.

Key Considerations for AVAPS Implementation

• The device has the potential advantage of automatically varying the pressure support to deliver a targeted tidal volume, which is beneficial if respiratory muscle strength declines and the tidal volume decreases 1.
• Relatively few studies on volume targeted VT-BPAP devices have been published, and recommendations are confined to the Average Volume Assured Pressure Support (AVAPS) device, which is the only VT-BPAP device available in the United States 1.
• AVAPS differs from standard BiPAP by focusing on volume targets rather than fixed pressures, which helps prevent hypoventilation while minimizing the risk of excessive pressure delivery.

Clinical Application of AVAPS

• AVAPS is primarily used for patients with chronic respiratory failure, obesity hypoventilation syndrome, COPD, and neuromuscular disorders who need ventilatory support but don't require intubation.
• Patients often find AVAPS more comfortable than conventional volume-targeted ventilation because pressure changes occur gradually over several breaths rather than breath-by-breath.
• Clinicians should set a target tidal volume, minimum and maximum pressure support limits, and respiratory rate when implementing AVAPS, and the system will automatically adjust pressure support between the set limits to achieve the target volume.

From the Research

Overview of AVAPS

• AVAPS (Average Volume Assured Pressure Support) is a mode of non-invasive ventilation that integrates the characteristics of both volume and pressure-controlled modes of ventilation 2, 3.
• AVAPS mode has been compared to BiPAP (Bilevel Positive Airway Pressure) spontaneous/timed mode in several studies, with results showing that AVAPS mode can lead to more rapid and steady improvement in patients with chronic obstructive pulmonary disease (COPD) and hypercapnic respiratory failure 2, 3, 4.

Comparison of AVAPS and BiPAP Modes

• A study published in Cureus found that AVAPS mode resulted in statistically significant improvements in pH and pCO2 levels compared to BiPAP spontaneous/timed mode in patients with acute exacerbation of COPD with type 2 respiratory failure 2.
• Another study published in BMC Pulmonary Medicine found that BiPAP S/T with AVAPS mode facilitated rapid recovery of consciousness in patients with COPD and hypercapnic encephalopathy compared to traditional BiPAP S/T mode 3.
• A randomized controlled trial published in the Balkan Medical Journal found that AVAPS mode was as effective and safe as BPAP S/T mode in treating patients with hypercapnic respiratory failure in the emergency department 4.

Mechanism of Action

• AVAPS mode uses a fixed tidal volume that automatically adjusts to a patient's needs, allowing for more precise control of ventilation 3, 5.
• The use of AVAPS mode can help to reduce the need for invasive mechanical ventilation and improve patient outcomes 2, 4.

Clinical Applications

• AVAPS mode has been used in the treatment of patients with COPD and hypercapnic respiratory failure, with positive results 2, 3, 4.
• The use of AVAPS mode may also be beneficial in other clinical settings, such as in the treatment of patients with acute respiratory distress syndrome (ARDS) 6.
• A study published in Internal and Emergency Medicine found that auto-titrating noninvasive ventilation (NIV) with AVAPS mode decreased PaCO2 more efficiently and rapidly in hypercapnic ICU patients compared to volume-assured mode 5.