Thoracic weighting of restrained subjects during exhaustion recovery causes loss of lung reserve volume in a model of police arrest

AbstractRestraint asphyxia has been proposed as a mechanism for some arrest-related deaths that occur during or shortly after a suspect is taken into custody. Our analysis of the literature found that prone positioning, weight applied to the back, recovery after simulated pursuit, and restraint position have led to restrictive, but non life-threatening respiratory changes when tested in subsets. However, the combined effects of all four parameters have not been tested together in a single study. We hypothesized that a complete protocol with high-sensitivity instrumentation could improve our understanding of breathing physiology during weighted restraint. We designed an electrical impedance tomography (EIT)-based protocol for this purpose and measured the 3D distribution of ventilation within the thorax. Here, we present the results from a study on 17 human subjects that revealed FRC declines during weighted restrained recovery from exercise for subjects in the restraint postures, but not the control posture. These prolonged FRC declines were consistent with abdominal muscle recruitment to assist the inspiratory muscles, suggesting that subjects in restraint postures have increased work of breathing compared to controls. Upon removal of the weighted load, lung reserve volumes gradually increased for the hands-behind-the-head restraint posture but continued to decrease for subjects in the hands-behind-the-back restraint posture. We discuss the possible role this increased work of breathing may play in restraint asphyxia.

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A High Accuracy and High Sensitivity System Architecture for Electrical Impedance Tomography System

2018 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS) ◽

10.1109/apccas.2018.8605564 ◽

2018 ◽

Cited By ~ 2

Author(s):

Hui Li ◽

Boxiao Liu ◽

Yongfu Li ◽

Guoxing Wang ◽

Yong Lian

Keyword(s):

Electrical Impedance Tomography ◽

System Architecture ◽

Electrical Impedance ◽

High Sensitivity ◽

High Accuracy ◽

Impedance Tomography ◽

Tomography System

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Electrical Impedance Tomography for Assessment of Pendelluft and Work of Breathing in Spontaneously Breathing Mechanically Ventilated Patients

10.1164/ajrccm-conference.2021.203.1_meetingabstracts.a2803 ◽

2021 ◽

Author(s):

E. Kistler ◽

M.S. Schaefer ◽

E. Baedorf Kassis

Keyword(s):

Electrical Impedance Tomography ◽

Electrical Impedance ◽

Work Of Breathing ◽

Impedance Tomography ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

Spontaneously Breathing ◽

Ventilated Patients

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Self-Abrading Servo Electrode Helmet for Electrical Impedance Tomography

Sensors ◽

10.3390/s20247058 ◽

2020 ◽

Vol 20 (24) ◽

pp. 7058

Author(s):

James Avery ◽

Brett Packham ◽

Hwan Koo ◽

Ben Hanson ◽

David Holder

Keyword(s):

Acute Stroke ◽

Electrical Impedance Tomography ◽

Large Scale ◽

Electrical Impedance ◽

Applied Pressure ◽

High Sensitivity ◽

Haemorrhagic Stroke ◽

Contact Impedance ◽

Impedance Tomography ◽

Skin Contact

Electrical Impedance Tomography (EIT) is a medical imaging technique which has the potential to reduce time to treatment in acute stroke by rapidly differentiating between ischaemic and haemorrhagic stroke. The potential of these methods has been demonstrated in simulation and phantoms, it has not yet successfully translated to clinical studies, due to high sensitivity to errors in scalp electrode mislocation and poor electrode-skin contact. To overcome these limitations, a novel electrode helmet was designed, bearing 32 independently controlled self-abrading electrodes. The contact impedance was reduced through rotation on an abrasive electrode on the scalp using a combined impedance, rotation and position feedback loop. Potentiometers within each unit measure the electrode tip displacement within 0.1 mm from the rigid helmet body. Characterisation experiments on a large-scale test rig demonstrated that approximately 20 kPa applied pressure and 5 rotations was necessary to achieve the target 5 kΩ contact impedance at 20 Hz. This performance was then replicated in a simplified self-contained unit where spring loaded electrodes are rotated by servo motors. Finally, a 32-channel helmet and controller which sequentially minimised contact impedance and simultaneously located each electrode was built which reduced the electrode application and localisation time to less than five minutes. The results demonstrated the potential of this approach to rapidly apply electrodes in an acute setting, removing a significant barrier for imaging acute stroke with EIT.

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Assessment and Calibration of a Low-Frequency System for Electrical Impedance Tomography (EIT), Optimized for Use in Imaging Brain Function in Ambulant Human Subjects

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1999.tb09500.x ◽

1999 ◽

Vol 873 (1 ELECTRICAL BI) ◽

pp. 512-519 ◽

Cited By ~ 15

Author(s):

D. S. HOLDER ◽

C. A. GONZALEZ-CORREA ◽

T. TIDSWELL ◽

A. GIBSON ◽

G. CUSICK ◽

...

Keyword(s):

Electrical Impedance Tomography ◽

Brain Function ◽

Electrical Impedance ◽

Human Subjects ◽

Low Frequency ◽

Impedance Tomography

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Combined effects of body positioning and noninvasive ventilation on the regional distribution of pulmonary ventilation evaluated by electrical impedance tomography in the young and the elderly

10.1183/13993003.congress-2019.pa2325 ◽

2019 ◽

Author(s):

Liegina Silveira Marinho ◽

Andrea Nobrega Cirino Nogueira Da Nobrega Cirino Nogueira ◽

Juliana Arcanjo Lino ◽

Gabriela De Carvalho Gomes Frota ◽

Renata Dos Santos Vasconcelos ◽

...

Keyword(s):

Electrical Impedance Tomography ◽

Noninvasive Ventilation ◽

Electrical Impedance ◽

Pulmonary Ventilation ◽

Regional Distribution ◽

The Elderly ◽

Combined Effects ◽

Impedance Tomography ◽

Body Positioning

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A Comparison of Bound-Constrained and Positivity-Constrained Optimization Method to Estimate Head Tissue Conductivities by Scalp Voltage Information

International journal of electrical and computer engineering systems ◽

10.32985/ijeces.10.1.4 ◽

2019 ◽

Vol 10 (1) ◽

pp. 25-33

Author(s):

Taweechai Ouypornkochagorn ◽

Chollanant Khattiyawech ◽

Natnicha Keatsiritawon

Keyword(s):

Constrained Optimization ◽

Electrical Impedance ◽

Grey Matter ◽

High Sensitivity ◽

Optimization Method ◽

Noninvasive Method ◽

Dimensional Model ◽

Impedance Tomography ◽

Unexpected Outcome ◽

Very High

Electrical Impedance Tomography (EIT) is a noninvasive method used to estimate the conductivity of head tissues. Estimation based on the unconstrained Gauss-Newton (GN) method is conventional, but it may result in negative-value or extraordinary high-value estimates, which are unexpected. In this study, the bound-constrained method and the positivity-constrained optimization method were investigated and compared to the unconstrained optimization method. A two-dimensional model was created for conductivity estimation containing five head tissues, i.e., the scalp, the skull, the cerebrospinal fluid (CSF), grey matter (GM), and white matter (WM). The results showed that the accuracy, the robustness, and the estimation convergence of the estimation of this approach were significantly improved by constraining. All unexpected values also disappeared. The investigation proved that very high sensitivity of the skull region caused the unexpected outcome of the unconstrained cases. This high sensitivity can be significantly reduced by constraining. However, a degree of estimation nonlinearity can be increased by constraining as well, causing some estimation accuracies in the case of the positivity-constrained optimization method to be poor. Therefore, it is recommended to use only the bound-constrained optimization method.

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