= Plateau airway pressure
{title2=$P_{\rm plat}$}
\b[Plateau airway pressure], $P_{\rm plat}$, is the airway pressure assessed during an end-inspiratory interval with no flow and sufficiently stable conditions. An <end-inspiratory hold> can allow the airway and communicating alveolar gas pressures to equilibrate when the respiratory system is passive and the circuit is not leaking.<Measured values for Ppeak and Pplateau by Hamilton Medical>[Definition of airway pressures; Principles of measuring plateau pressures]{ref}<How to measure driving pressure by Hamilton Medical>[Measurement conditions]{ref}
The distinction from <peak airway pressure> follows a simple single-compartment model:
$$
p_{\rm aw}=P_{\rm EEP,total}+\frac{V}{C}+R\dot V.
$$
During the modeled hold, $\dot V=0$, leaving
$$
P_{\rm plat}=P_{\rm EEP,total}+\frac{V_T}{C}.
$$
Here $C$ is <respiratory-system compliance>, $R$ is <airway resistance>, and total <positive end-expiratory pressure> supplies the starting reference. The measured difference $P_{\rm plat}-P_{\rm EEP,total}$ is the corresponding <respiratory driving pressure>.
In an original example, total PEEP 8 cm H$_2$O, <tidal volume> 0.40 L and compliance 0.04 L/cm H$_2$O give $P_{\rm plat}=18$ cm H$_2$O. If flow immediately beforehand is 0.5 L/s and resistance is 12 cm H$_2$O·s/L, the model's airway pressure during that flow is 24 cm H$_2$O. The 6 cm H$_2$O difference is the modeled resistive contribution, not an extra static distending pressure.
A plateau does not directly measure <pleural pressure> or isolate the lung from the chest wall. For the same stipulated alveolar pressure 18 cm H$_2$O, pleural pressures of 12 and 2 cm H$_2$O imply <transpulmonary pressures> of 6 and 16 cm H$_2$O. The airway value alone cannot distinguish those states.
Finally, a stable displayed number is not automatically the same operation as an actual hold. The manufacturer distinguishes measured holds, rapid occlusion and calculated monitoring estimates.<Measured values for Ppeak and Pplateau by Hamilton Medical>[Principles of measuring plateau pressures; Monitoring parameter Pplateau]{ref} Reporting the method and its conditions connects <plateau airway pressure> to the mechanical question it can answer.
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