Key points are not available for this paper at this time.
Changes in anteroposterior diameters of the rib cage and abdomen are sensed with magnetometers and summed to give outputs which are very nearly linearly related to changes in lung volume. The volume events of breathing can be measured without recourse to a mouthpiece or face mask, other than for calibration, and with minimal encumbrance to the subject.
Mead et al. (Fri,) studied this question.