The one-way endobronchial valve is typically implanted such that on exhalation air is able to flow through the valve and out of the lung compartment that is fed by that airway, but on inhalation, the valve closes and blocks air from entering that lung compartment. Thus, an implanted endobronchial valve typically helps a lung compartment to empty itself of air. This has been shown to be beneficial in the treatment of emphysema, where lungs lose their elasticity and thus cannot contract sufficiently to exhale air, leading to air trapping and hyperinflation.
A one-way endobronchial valve is usually inserted so that air can escape from a lung compartment connected to it during breathing out, but it closes during breathing in, preventing air from entering that compartment. This mechanism enables the lung compartment to release its air content, which has been found to be helpful in treating emphysema.