Estimation of respiratory variables from thoracoabdominal breathing distance a review of different techniques and calibration methods

International audienceThe precise measurement of respiratory variables, such that tidal volume, minute ventilation, respiratory rate is necessary to monitor respiratory status to overcome several diseases, improve patient health conditions and reduce health care costs. This measurement has conventionally been performed by breathing into a mouthpiece connected to a flow rate measuring device. However, a mouthpiece is uncomfortable for the subject and it is difficult to use for long term monitoring. Other noninvasive systems and devices have been developed that do not require a mouthpiece to quantitatively measure respiratory variables. These techniques are based on measuring size changes of the rib cage (RC) and abdomen (ABD), as lung volume is known to be a function of these variables. Among these systems, we distinguish respiratory inductive plethysmography (RIP), respiratory magnetometer plethysmography (RMP), and optoelectronic plethysmography devices. However, they should be previously calibrated for correct evaluation of respiratory variables. The most popular calibration methods are isovolume maneuver calibration (ISOCAL), qualitative diagnostic calibration (QDC), multiple linear regression (MLR) and artificial neural networks (ANNs). The aim of this review is firstly to present how thoracoabdominal breathing distances can be used to estimate respiratory variables and secondly to present the different techniques and calibration methods used for this purpose.and#13