A pneumograph, also known as a pneumatograph or spirograph, is a device for recording velocity and force of chest movements during respiration.

In one mechanism, a flexible rubber vessel is attached to the chest.

The vessel is equipped with sensors such as accelerometers, piezoelectric sensors, or a fiber Bragg grating[1] to measure chest motion and obtain respiratory rate.

In these methods, a high-frequency (tens to hundreds of kHz), low-amplitude current is injected across the chest cavity.

The voltage resulting from this current injection is measured and the resistance is derived from the application of Ohm's Law: