ΔP

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This article is about the mathematical term used in fluid dynamics. For the concept of delta-P in diving safety, see Diving hazards.

ΔP (Delta P) is a mathematical term symbolizing a change (Δ) in pressure (P).

Uses

Darcy–Weisbach equation

Given that the

head loss hf expresses the pressure
loss Δp as the height of a column of fluid,

where ρ is the density of the fluid. The Darcy–Weisbach equation can also be written in terms of pressure loss:

Lung compliance

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:

  1. Lung compliance
  2. Chest wall compliance
  3. Airway resistance

Lung compliance is influenced by a variety of primary abnormalities of

morbid obesity) or more variable problems driven by patient agitation while intubated.[1]

Calculating compliance on

minute volume (VE: ΔV is always defined by tidal volume
(VT), but ΔP is different for the measurement of dynamic vs. static compliance.

Dynamic compliance (Cdyn)

where PIP =

positive end expiratory pressure. Alterations in airway resistance, lung compliance
and chest wall compliance influence Cdyn.

Static compliance (Cstat)

where Pplat = plateau pressure. 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. Pplat is never > PIP and is typically < 3-5 cmH2O lower than PIP when airway resistance is normal.

See also

References

  1. S2CID 36231036
    .

External links
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