Comparison of two- and four-magnetometer methods of measuring ventilation

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Abstract
Two computerized methods of measuring ventilation from 4 pairs of magnetometers placed anteroposteriorly (AP) and laterally on the rib cage and abdomen were compared with a method that employs 2 pairs of magnetometers placed AP on the rib cage and abdomen. The most accurate method of measuring ventilation employed 4 magnetometer pairs and a model that assumes the rib cage and abdomen to be approximated by elliptical cylinders. In 10 [human] subjects of widely varying body habitus, this method accurately predicted lung volume change during quiet breathing (r [correlation coefficient] > 0.98) and during vital capacity maneuvers (r > 0.97). The rib cage contributes the majority (74%) of the volume change in the upright position. This method is sufficienctly accurate to be used as a method of monitoring ventilation under a wide variety of tidal volumes, postures and exercise states.