Static & Dynamic Compliance
Separate the elastic problem from the resistive one — Cstat, Cdyn, and airway resistance from the pressures on the screen.
Written by Apex Respiratory Editorial Team
From an inspiratory hold.
Optional — adds Raw (constant flow).
Enter VT, PEEP, and a plateau and/or peak pressure.
Reading the Cdyn–Cstat split
Both falling together → an elastic (lung/chest wall) problem: ARDS, edema, pneumothorax, atelectasis, abdominal pressure. Cdyn falling with a stable Cstat (the PIP−Pplat gap widening) → a flow-resistance problem: secretions, bronchospasm, a kinked or narrowing tube.
Measure Pplat with an inspiratory hold in a passive patient, and use total PEEP when auto-PEEP is present. Normal ventilated adults run roughly 40–80 mL/cmH₂O; healthy lungs 50–100+.
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Sources
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021. Pulmonary mechanics chapters.
- NIH NHLBI ARDS Clinical Network. Mechanical ventilation protocol summary (plateau pressure goal ≤ 30 cmH₂O). ARDSnet; 2008.