Diffuse optical monitoring of peripheral tissues during uncontrolled internal hemorrhage in a porcine model

Investigation of a Ballistocardiogram-Based Technique for Unobtrusive Monitoring of Fluid Accumulation in the Body. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020;2020:5146-5149. [PMID: 33019144 DOI: 10.1109/embc44109.2020.9176094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

We introduce a novel monitoring solution for fluid accumulation in the human body (e.g. internal bleeding), based on observation of a selected energy-describing feature of the Ballistocardiogram (BCG) signal. It is hypothesized that, because of additional damping generated by the fluid, BCG signal energy decreases as compared to its baseline value. Data were collected from 15 human volunteers via accelerometers attached to the participants' body, and an electromechanical-film (EMFi) sensor-equipped bed. Fluid accumulation along the gastrointestinal (GI) tract was induced by means of water intake by the participants, and the BCG signal was recorded before and after intake. Based on performance evaluation, we selected a suitable energy feature and sensing channel amongst the ones investigated. The chosen feature showed a significant decrease in signal energy from baseline to after-intake condition (p-value<0.001), and identified the presence of fluid accumulation with high sensitivity (90% in bed-based, and 100% in standing-position monitoring).

mHealth spectroscopy of blood hemoglobin with spectral super-resolution

Although blood hemoglobin (Hgb) testing is a routine procedure in a variety of clinical situations, noninvasive, continuous, and real-time blood Hgb measurements are still challenging. Optical spectroscopy can offer noninvasive blood Hgb quantification, but requires bulky optical components that intrinsically limit the development of mobile health (mHealth) technologies. Here, we report spectral super-resolution (SSR) spectroscopy that virtually transforms the built-in camera (RGB sensor) of a smartphone into a hyperspectral imager for accurate and precise blood Hgb analyses. Statistical learning of SSR enables us to reconstruct detailed spectra from three color RGB data. Peripheral tissue imaging with a mobile application is further combined to compute exact blood Hgb content without a priori personalized calibration. Measurements over a wide range of blood Hgb values show reliable performance of SSR blood Hgb quantification. Given that SSR does not require additional hardware accessories, the mobility, simplicity, and affordability of conventional smartphones support the idea that SSR blood Hgb measurements can be used as an mHealth method.

Use of infrared thermography to detect early alterations of peripheral perfusion: evaluation in a porcine model

This study aimed to evaluate the variations of infrared thermography according to rapid hemodynamic changes, by measuring the peripheral skin temperature in a porcine model. Eight healthy piglets were anesthetized and exposed to different levels of arterial pressure. Thermography was performed on the left forelimb to measure carpus and elbow skin temperature and their associated gradient with the core temperature. Changes in skin temperature in response to variations of blood pressure were observed. A negative correlation between arterial pressure and temperature gradients between peripheral and core temperature and a negative correlation between cardiac index and these temperature gradients were observed. Thermography may serve as a tool to detect early changes in peripheral perfusion.

Small separation diffuse correlation spectroscopy for measurement of cerebral blood flow in rodents

Diffuse correlation spectroscopy (DCS) has shown promise as a means to non-invasively measure cerebral blood flow in small animal models. Here, we characterize the validity of DCS at small source-detector reflectance separations needed for small animal measurements. Through Monte Carlo simulations and liquid phantom experiments, we show that DCS error increases as separation decreases, although error remains below 12% for separations > 0.2 cm. In mice, DCS measures of cerebral blood flow have excellent intra-user repeatability and strongly correlate with MRI measures of blood flow (R = 0.74, p<0.01). These results are generalizable to other DCS applications wherein short-separation reflectance geometries are desired.