In positive pressure ventilation, what occurs at the end of inspiration?

At the end of inspiration in positive pressure ventilation, the mouth pressure returns to ambient pressure. This occurs because the positive pressure applied by the ventilator during inspiration is released, allowing the pressure in the airway and mouth to equalize with the atmospheric pressure outside the body.

In positive pressure ventilation, air is pushed into the lungs, creating a pressure difference that allows for the inflow of air. Once the ventilator cycle is complete and the inspiratory phase ends, there is no longer a force exerted by the ventilator to maintain that increased pressure. Hence, as the ventilator stops delivering breaths, the pressures equilibrate, leading to a return to ambient pressure in the mouth.

This process is critical, as it sets the stage for the next phase of the respiratory cycle, which is exhalation, allowing the alveoli to return to a baseline or atmospheric pressure, facilitating gas exchange.