Albert Ruiz-Vargas

Although biomedical engineering (BME) is a profession with ethical responsibilities comparable to those in medicine, it has, until now, lacked a counterpart to the Hippocratic Oath. While professional societies have established codes of ethics for biomedical engineers, these documents lack the symbolic and ceremonial significance of an oath or pledge. By contrast, the recitation of the Hippocratic Oath, or its modern version, the “Physician’s Pledge,” serves as a powerful rite of passage for medical students, fostering a strong sense of ethical duty at the start of their professional journey. However, the content of the Hippocratic Oath includes elements specific to clinical practice and is not directly applicable to biomedical engineering. To fill this gap, we have created a “Biomedical Engineer’s Pledge,” comprising a preamble, ten promises, and a concluding statement, to inspire ethical awareness and establish a meaningful graduation tradition. Graphical abstract

Continuous monitoring of intrapulse measurement of blood flow in humans is currently not achievable with clinically available instruments. In this paper, we demonstrate a method of measuring the instantaneous variations in flow during pulsatile blood flow with an optical flow sensor comprising a fiber Bragg grating sensor and illumination from a 565 nm Light‐Emitting‐Diode. The LED illumination heats the blood and fluctuations in temperature, due to variations in flow, are detected by the fiber sensor. A set of experiments at different flow rates (20 to 900 mL/min) are performed in a simulated cardiac circulation setup with pulsatile flow. Data are compared with an in‐line time of flight ultrasound flow sensor. Our results show that the optical and ultrasonic signals correlate with Pearson coefficients ranging from −0.83 to −0.98, dependent on the pulsatile frequency. Average flow determined by ultrasound and the optical fiber sensor showed a parabolic relationship with R² = 0.99. An abrupt step change in flow induced by occlusion and release of the circuit tubing demonstrated that the optical fiber and ultrasound sensor had similar response. The method described is capable of intrapulse blood flow measurement under pulsatile flow conditions, with potential applications in medicine where continuous blood flow sensing is desired.

Background: High‐resolution impedance manometry (HRIM) catheters are used for esophageal reflux and bolus transit studies. Usually, these catheters have electrodes spaced at 20 mm intervals that are used for measuring electrical impedance between the consecutive electrodes and pressure sensors with 10 mm separation. Electrical impedance is a distributed measurement between the electrodes, unlike the point measurement of pressure sensors. Thus, the electrode separations affect the overall spatiotemporal resolution of the measurement.Methods: A 3D model of the gastrointestinal tract, in which bolus shape and size can be modified, was used to simulate the admittance signal response of an intraluminal impedance catheter with 10 and 20 mm electrode separation to study the distributed sensitivity in the lumen to gain insight on the impedance measurement. In addition, experiments on sections of rabbit proximal colon were conducted with two catheters with electrode separations of 10 and 20 mm to compare the experimental data with the simulated data.Key Results: Reducing electrode spacing from 20 to 10 mm increased sensitivity to diameter change by a factor of ten. Admittance and diameter correlated strongly during a myogenic contraction with a Pearson's Correlation Coefficient of 0.86 for the custom catheter, in comparison with 0.56 for the commercial HRIM catheter.Conclusions: Ten millimeter electrode separation has a better spatiotemporal resolution, and unlike 20 mm electrode separation is able to identify myogenic contractions. Based on the numerical and experimental data, closer electrode separation should be considered for improved spatial resolution.

Bioimpedance spectroscopy measurements can be used for tissue characterization. These measurements can be performed in soft tissues by direct contact of a non-invasive probe consisting of two or four electrodes. The amount of force applied by users can be quite different, and the measurements can vary as a result. To compensate for this, we have built an electrical impedance probe (diameter 3.2 mm) with fibre optic contact-force and temperature sensors built in it. The different sensors of the probe were tested individually. The errors in magnitude and phase angle of the probe are ex-vivo experiment on a section of proximal colon from a guinea-pig was performed. Twenty bioimpedance measurements were taken in a frequency range of 5 kHz to 1 MHz, while simultaneously recording the force applied. For an increase in contact pressure applied to tissue from 0 to 15.4 kPa, the maximum change in resistivity was 33% at 5 kHz and the minimum was 6.6% at 142 kHz. The probe is small enough to be introduced via the instrument port of an endoscope.

Errors in peak wavelengths from fiber Bragg gratings (FBGs) when monitored using a pixel based solid state spectrometer have been investigated. These errors show a pseudo-sinusoidal ripple superimposed upon the expected linear response. The error is analogous to a peak-locking effect common to sub-pixel resolution particle tracking by CCD camera in particle image velocimetry. The amplitude of the error is calibrated as a proportion of the scaled variation of the change in the peak power of the calculated peak as the spectral peak is scanned across the pixel array. An error correction algorithm has been developed and verified in order to provide an increase in accuracy of sensing solutions when using pixel based spectrometers. The methods presented here permit the correction of pixel induced ripple errors in real time using data commonly available from many interrogation spectrometers. Calibration prior to use can be achieved by scanning each FBG spectral peak across the width of a single pixel. The proposed method of error correction is applied to a fiber optic sensor array utilized for biomedical pressure and temperature measurement and demonstrates a clear ability to increase the accuracy of measured signals.

Background: Intraluminal electrical impedance is a well‐known diagnostic tool used to study bolus movement in the human esophagus. However, it is use in the human colon it is hindered by the fact that the content cannot be controlled and may include liquid, gas, solid, or a mixture of these at any one time. This article investigates the use of complex impedance spectroscopy to study different luminal content (liquid and gas).Methods: An excised section of guinea pig proximal colon was placed in an organ bath with Krebs solution at 37°C and a custom built bioimpedance catheter was placed in the lumen. Liquid (Krebs) and gas (air) content was pumped through the lumen and the intraluminal impedance was measured at five different frequencies (1, 5.6, 31.6, 177.18 kHz and 1 MHz) at 10 samples per second. A numerical model was created to model the passage of bolus with different content and compared to the experimental data.Key Results: Differences in mean impedance magnitude and phase angle were found (from 1 to 177.18 kHz) for different contents. The numerical results qualitatively agreed with those in the experimental study. Conductivities of bolus had an effect on detecting its passage.Conclusions & Inferences: Complex impedance spectroscopy can distinguish between different luminal content within a range of measuring frequencies. The numerical model showed the importance of bolus conductivities for bolus transit studies in those where the bolus is controlled.