Comment on ‘Comparative analysis of the isovolume calibration method for non-invasive respiratory monitoring techniques based on area transduction versus circumference transduction using the connected cylinders model’ (2011 Physiol. Meas. 32 1265–74)
An analytical formalism developed previously to examine the robustness of the isovolume calibration technique for non-invasive respiratory monitoring devices based on measurements of torso circumference (e.g. fibre-optic respiratory plethysmography) is extended here to techniques based on area measurement (e.g. respiratory inductive plethysmography), and the results are compared. The earlier perturbation approach is adopted, and an exact method is also presented. It is demonstrated that the area-based techniques have less dependence on the cylindrical compartmental parameters of radius and height, and are independent of compartmental volume if height variations are negligible, in contrast to circumference-based techniques. It is also demonstrated that both the area- and the circumference-based techniques provide similar inferences of volume when calibrated using the isovolume method under reasonable assumptions for the dimensions of the compartments that constitute a model of the torso.
- [Show abstract] [Hide abstract] ABSTRACT: The use of the isovolume manoeuvre method as a calibration technique for respiratory monitoring instrumentation that detects the movement of the ribcage and the abdominal wall is analysed based on a model of two connected cylinders whose radii and heights may vary, and evidence is presented which suggests that this calibration method is robust in most circumstances. Some possible functional forms relating the variations in cylinder radius and height are examined, and methods for obtaining calibration constants based on these functional forms, purely from measurements of variations in the cylinder radius, are presented.0Comments 7Citations
- [Show abstract] [Hide abstract] ABSTRACT: A fiber optic sensor for the measurement of the respiratory depth has been developed. The sensor is composed of a bent optic fiber which is connected to an elastic section of a chest belt so that its radius of curvature changes during respiration due to respiratory chest circumference changes (RCCC). The measurement of light transmission through the bent fiber provides information on its changes in curvature since a higher fraction of light escapes through the core-cladding surface of a fiber bent to a lower radius of curvature. The sensor can quantitatively measure the RCCC, although in relative terms, and it is sensitive enough to detect changes of the chest circumference due to the heart beat. Measurements of the RCCC were simultaneously performed with photoplethysmography (PPG)-the measurement by light absorption of the cardiac induced blood volume changes in the tissue-and a significant correlation was found between the RCCC and some parameters of the PPG signal. The fiber optic respiratory depth sensor enables a quantitative assessment of the respiratory induced changes in the cardiovascular parameters. © 1999 Society of Photo-Optical Instrumentation Engineers.0Comments 28Citations
- [Show abstract] [Hide abstract] ABSTRACT: The macro-bending loss effect in optical fibres has been used to redevelop a sensor for the measurement of thoracic and abdominal circumferences in non-invasive respiratory monitoring. The new sensor uses a novel figure-of-eight loop configuration, which results in increased linearity of response, less mechanical resistance and hysteresis, as well as other benefits. The performance of the new sensor as applied to respiratory monitoring is examined, and indicates a higher resolution and sensitivity than the old. This enhanced performance enables measurement of respiratory and cardiac function using the same transducing fibre.0Comments 29Citations