ΔP (Delta P) is a mathematical term symbolizing a change (Δ) in pressure (P).
The Darcy–Weisbach equation can also be written in terms of pressure loss: In general, compliance is defined by the change in volume (ΔV) versus the associated change in pressure (ΔP), or ΔV/ΔP: During mechanical ventilation, compliance is influenced by three main physiologic factors: Lung compliance is influenced by a variety of primary abnormalities of lung parenchyma, both chronic and acute.
Chest wall compliance can be decreased by fixed abnormalities (e.g. kyphoscoliosis, morbid obesity) or more variable problems driven by patient agitation while intubated.
Pplat is measured at the end of inhalation and prior to exhalation using an inspiratory hold maneuver.
During this maneuver, airflow is transiently (~0.5 sec) discontinued, which eliminates the effects of airway resistance.