Using body surface movements to study breathing.

The chest wall comprising both rib cage and abdomen moves during breathing, and when suitably calibrated this motion can be used to monitor pulmonary ventilation without the need for face-masks or mouthpieces. Such non-invasive methods of studying breathing are likely to become more widely used in the future, especially in the investigation of respiratory control and sleep-disordered breathing. This review describes the physiological basis of these measurements and examines the practical and theoretical limitations of calibration techniques based on the two degrees-of-freedom model of chest-wall motion.