What is the formula for calculating static compliance?

Static compliance is a measure used in respiratory medicine to assess the ability of the lungs and thoracic cavity to expand in response to a given pressure change. The correct formula for calculating static compliance is based on the relationship between volume and pressure, specifically during a static or unchanging pressure scenario.

The formula for static compliance is Volume (Vt) divided by the difference in plateau pressure (Plat) and end-expiratory pressure (PEEP). In this formula, Vt represents the tidal volume, which is the amount of air that is inhaled or exhaled during each respiratory cycle. Plateau pressure is measured during a period of no airflow, reflecting the pressure in the alveoli after a sustained breath, while PEEP is the pressure in the airways at the end of expiration.

This relationship helps identify how compliant the lungs are under static conditions and is important for understanding respiratory mechanics in critically ill patients. Higher compliance indicates less pressure is needed to move a given volume of air, while lower compliance suggests increased resistance to airflow, which can occur in various lung pathologies.