Lung Compliance Calculator

The Lung Compliance Calculator estimates lung elasticity in mL/cm H₂O based on volume change and pressure change. This tool helps medical professionals and students quickly assess respiratory mechanics for better patient care. Whether you are diagnosing restrictive lung disease, checking for obstructive conditions, or monitoring critical care patients, this tool provides instant, reliable results for clinical decisions.

Enter the volume change in milliliters (mL)
Enter the pressure change in centimeters of water (cm H₂O)
Choose between static (no airflow) or dynamic (during airflow) compliance

How Lung Compliance Is Calculated

Lung compliance measures how easily the lungs stretch and expand when pressure changes. It shows the relationship between the volume of air you can breathe in and the pressure needed to push it in. This calculation is vital because it reveals lung stiffness, helping doctors spot problems early.

Compliance = ΔV / ΔP

Where:

  • ΔV = Change in Lung Volume (mL)
  • ΔP = Change in Transpulmonary Pressure (cm H₂O)

First, determine the change in lung volume (ΔV) in milliliters during a breath. Next, find the change in transpulmonary pressure (ΔP) in cm H₂O. Finally, divide the volume change by the pressure change. This standard medical method ensures you get an accurate picture of respiratory mechanics.

What Your Lung Compliance Means

This number tells you exactly how stretchy or stiff the lungs are during the breathing process. A higher result means the lungs expand easily with little effort, while a lower result indicates they are stiff and hard to inflate.

Normal Lung Function: For static compliance, a range of 60-100 mL/cm H₂O suggests healthy lung elasticity. Dynamic compliance is normal between 50-80 mL/cm H₂O during active breathing.

Restrictive Lung Disease: Values below 60 mL/cm H₂O typically mean the lungs are stiff. This often happens in conditions like pulmonary fibrosis where lung tissue is tight, thick, and scarred.

High Compliance: Values above 100 mL/cm H₂O may suggest a loss of elastic recoil. This is common in emphysema where lungs trap air and over-expand too easily.

Important Note: Always distinguish between static (no airflow) and dynamic (during airflow) results, as normal ranges differ slightly between the two types.

Disclaimer: This calculator is a screening tool for educational purposes and is not a substitute for professional medical diagnosis or treatment. Always consult a qualified healthcare provider to interpret results and plan patient care.

Monitor changes in compliance values over time to track disease progression or the effectiveness of treatments like ventilation adjustments.