= Pierre Tawfik
{c}
\b[<Pierre Tawfik>] is first author of a 2022 pilot study comparing static and dynamic estimates of <respiratory-system compliance> and driving pressure during passive <mechanical ventilation>.<Static and Dynamic Measurements of Compliance and Driving Pressure: A Pilot Study by Pierre Tawfik and others>[Primary byline; Study Design]{ref} The distinction concerns how pressure and volume are sampled, rather than two names for an automatically identical material constant.
The paper compared methods using equilibrated plateau pressure, the first zero-flow pressure, the pressure-volume slope during constant-flow inflation and expiratory time constants.<Static and Dynamic Measurements of Compliance and Driving Pressure: A Pilot Study by Pierre Tawfik and others>[Introduction and Figure 1, methods A–D]{ref} Its results concern the respiratory system, including the <lungs> and chest wall; they should not silently be relabeled as <lung compliance> alone.
An original quasistatic model illustrates the boundary distinction. If the same volume change stretches the lungs and chest wall, their required pressure changes add:
$$
\Delta P_{\rm rs}=\Delta V\left(\frac1{C_L}+\frac1{C_W}\right),\qquad
\frac1{C_{\rm rs}}=\frac1{C_L}+\frac1{C_W}.
$$
Here $C_L$ is <lung compliance> and $C_W$ <chest-wall compliance>. At stipulated $C_L=0.10$ and $C_W=0.20\,\mathrm{L}/(\mathrm{cm\ H_2O})$, the system compliance is approximately $0.0667\,\mathrm{L}/(\mathrm{cm\ H_2O})$. A 0.50 L change needs 7.5 cm of water across the combined elastic system, of which 5 belongs to the lung term. These are chosen linear-model values, not measurements from Tawfik's cohort.
During flow, an additional resistive pressure contribution can occur. Relaxation after flow stops can also change the observed pressure. Consequently, specifying system boundaries and sampling time is necessary before interpreting a computed volume/pressure ratio. The primary experiment tests those methodological distinctions in the same clinical setting; the simple series-compliance calculation isolates only one reason why different quantities must be kept separate.
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