Towards a continuous non-invasive assessment of intra-abdominal pressure based on bioimpedance and microwave reflectometry: A pilot run on a porcine model

Non-invasive indirect monitoring of intra-abdominal pressure using microwave reflectometry: system design and proof-of-concept clinical trial

“…Reflectometry results over five laparoscopic surgery patients clearly show an inverse correlation between IAP and the reflection coefficient; these results are supported by theoretical considerations [14]. Even though the dielectric properties of tissues are well determined and have relatively low variance [23,24], different subjects usually have different widths of each abdominal layer, especially fat and skin [14,15]. It follows that the values of S 11 are expected to vary with the BMI, as seen in this trial (Fig.…”

“…A detailed description of the electromagnetic (dielectric) model of the abdominal wall is presented in [ 14 , 15 ]. For simplicity, the abdominal wall can be considered a compressible non-homogeneous anisotropic dielectric slab [ 20 – 22 ], which will be compressed as IAP increases and will, therefore, change its thickness.…”

“…For simplicity, the abdominal wall can be considered a compressible non-homogeneous anisotropic dielectric slab [ 20 – 22 ], which will be compressed as IAP increases and will, therefore, change its thickness. Previously published numerical analysis [ 14 ] suggests that such changes in the AWTh, correlate well with the reflection coefficient of the abdominal wall (called S 11 —input port reflection coefficient). S 11 is a ratio between the reflected power ( P reflected ) and transmitted power ( P transmitted ) at the antenna, usually measured in dB (Eq.…”

“…The abdominal wall mainly consists of five soft tissue layers as described in [16][17][18][19] [14,15]. For simplicity, the abdominal wall can be considered a compressible non-homogeneous anisotropic dielectric slab [20][21][22], which will be compressed as IAP increases and will, therefore, change its thickness.…”

“…Continuous monitoring of IAP has been researched by several groups in the past years [ 2 , 3 , 11 – 13 ], but no feasible or easy-to-use non-invasive method has reached clinical use yet [ 3 ]. In 2017, David et al [ 14 ] proposed a generic numerical electromagnetic model of the abdominal wall as for correlating abdominal wall’s thickness (AWTh) to microwave reflectometry. In 2018, David et al verified the theory by preliminary results on porcine models [ 15 ].…”