In mechanical ventilation, what conclusion can be drawn if peak inspiratory pressure increases but plateau pressure remains constant?

When peak inspiratory pressure increases while plateau pressure remains constant, this indicates a change in airflow resistance rather than a change in lung compliance. Peak inspiratory pressure reflects the total pressure required to deliver air to the lungs, which is influenced by both the resistance of the airways and the compliance of the lungs. The plateau pressure, on the other hand, reflects the pressure needed to inflate the lungs without airflow, thus it is a measure of lung compliance.

If the plateau pressure remains stable, it suggests that the lungs are compliant and the volume changes are not affecting lung distensibility. Consequently, if peak inspiratory pressure increases, it can only be attributed to increasing airway resistance. As the resistance increases, it requires more pressure to achieve the same flow rate of air into the lungs, explaining why the peak inspiratory pressure would rise while the plateau pressure remains unchanged. This scenario is typical in conditions such as bronchospasm or mucus plugging where airflow obstruction occurs without affecting the lung's ability to expand when not actively ventilating.