Respiratory inductance plethysmography
Respiratory inductance plethysmography (RIP) is a method of evaluating pulmonary ventilation by measuring the movement of the chest and abdominal wall. Accurate measurement of pulmonary ventilation or breathing often requires the use of devices such as masks or mouthpieces coupled to the airway opening.
Source: Wikipedia — Respiratory inductance plethysmography (CC BY-SA 4.0)