Flow-volume loop

Flow volume loop showing Peak, Forced Expiratory/Inspiratory Flows and Forced Vital Capacity

A flow-volume loop plots airflow rate vs volume. Peak Expiratory Flow (PEF) is the fastest exhalation - the most important value measured in this study. Forced Expiratory Flow (MEF) rates are also measured at different volumes.

Flow-Volume loops:

Deviations from the normal curve can indicate various abnormalities.

Restrictive disorders will decrease the available lung volume, but airflow willl increase. The loop will appear narrower.

In obstructive disorders (hard to breathe in), the same amount of volume will be left, but inspiratory airflow will decrease. The expiration curve will decrease compared to inspiration.

(use a different picture which will include a small loop in the middle. It represents normal respiration. Use picture that will include VI, ERV, RV, IRV

Also, normal graphs would be curved during expiration during resistance - it wont be linear. Note that FEV1 is not appropriate on this curve, it can be estimated, but not known.

Be able to draw this curve in case of obstructive and restrictive disorders. )

References

Wood, K., 2020. Airflow, Lung Volumes, and Flow-Volume Loop - Pulmonary Disorders - MSD Manual Professional Edition. [online] MSD Manual Professional Edition. Available at: <https://www.msdmanuals.com/professional/pulmonary-disorders/tests-of-pulmonary-function-pft/airflow,-lung-volumes,-and-flow-volume-loop> [Accessed 22 February 2022].