Pressure Support Mode in Non-Invasive Ventilation

Core Mechanism and Function

The American Thoracic Society recommends pressure support mode in non-invasive ventilation as a patient-triggered, pressure-controlled ventilation method that delivers a preset inspiratory positive airway pressure (IPAP) to assist each spontaneous breath, combined with a lower expiratory positive airway pressure (EPAP) 1
Pressure support ventilation operates as a bi-level system using two distinct pressure levels, including IPAP and EPAP, to provide pressure assistance during inspiration and maintain positive pressure during expiration 1, 2
The ventilator compensates automatically for air leakage, which is inevitable with non-invasive interfaces, and flow sensors detect changes in machine-produced bias flow to trigger breaths, allowing the ventilator to synchronize with patient effort 1, 4

The European Respiratory Society notes that pressure support mode overcomes intrinsic PEEP in COPD patients through EPAP, which offsets the recoil pressure of overinflated lungs and helps trigger breaths 1, 3
Pressure support mode improves oxygenation through lung recruitment encouraged by EPAP, according to the American College of Chest Physicians 1, 4

The British Thoracic Society recommends bi-level pressure support ventilators as simpler to use, cheaper, and more flexible than other types of ventilators currently available, and they have been used in the majority of randomized controlled trials of NIV 1, 2
The initial settings for IPAP and EPAP should be based on patient response, with typical EPAP levels ranging from 3-5 cm H₂O, although levels greater than 5 cm H₂O are rarely tolerated despite intrinsic PEEP potentially reaching 10-15 cm H₂O in severe COPD 1, 3

The American Association for Respiratory Care notes that significant rebreathing potential exists with bi-level systems, especially at low EPAP levels and high respiratory rates, which can paradoxically worsen hypercapnia in tachypneic, anxious patients who fail to improve 4, 5
Patient-ventilator asynchrony may result from undetected inspiratory effort, delayed response to start of inspiration, delayed detection of breath termination, or excessive air leakage, and when asynchrony cannot be resolved, consider switching to timed or assist-control mode 1, 3