During which conditions are compliance measurements for mechanical ventilation typically taken?

Compliance measurements for mechanical ventilation are typically taken during static or no-flow conditions because this the best way to evaluate the lung's ability to stretch and expand without the influence of airflow. Under these conditions, any pressure changes in the system are primarily due to the elastic properties of the lung and chest wall. It allows for an accurate calculation of compliance, which is the ratio of change in volume to a change in pressure (ΔV/ΔP).

When airflow is present, as in dynamic conditions, other forces come into play, including resistance and the effects of rapid gas flow, which complicates the measurement and may lead to inaccuracies in assessing lung compliance. Thus, the focus on static conditions ensures that measurements reflect the true mechanical characteristics of the respiratory system.