Overview
What Positive Pressure Changes
Non invasive ventilation (NIV) delivers positive pressure respiratory support through a nasal, oronasal, or total face interface rather than an endotracheal tube.
Non-invasive ventilation (NIV) delivers positive-pressure respiratory support through a nasal, oronasal, or total-face interface rather than an endotracheal tube. It can reduce the work of breathing, improve gas exchange, and sometimes avert intubation—but only when the patient can cooperate, protect their airway, and be watched closely enough to detect failure early. Bilevel NIV alternates between a higher inspiratory positive airway pressure (IPAP) and a lower expiratory positive airway pressure (EPAP). The difference between IPAP and EPAP is pressure support. It assists the patient’s inspiratory effort, increases tidal volume, improves alveolar ventilation, and promotes carbon dioxide elimination. For a patient with hypercapnic COPD whose respiratory muscles are tiring, pressure support is the part of bilevel therapy that matters most. EPAP also has an oxygenation role. By maintaining pressure at end-expiration, it helps prevent alveolar collapse and recruits fluid-filled or unstable alveoli. EPAP functions much like positive end-expiratory pressure in invasive ventilation. Continuous positive airway pressure (CPAP) delivers one pressure throughout inspiration and expiration. It improves oxygenation by splinting open alveoli and reducing atelectasis, but it does not add inspiratory assistance. CPAP...