1,720,995 research outputs found
Chest Wearable Apparatus for Cuffless Continuous Blood Pressure Measurements Based on PPG and PCG Signals
Full text linkThis paper describes an integrated chest wearable apparatus for continuous blood pressure (BP) measurements exploiting the heart-rate (HR) and the pulse arrival time (PAT) in a modified Moens-Korteweg model. The device embeds a miniaturized gas pressure sensor to record the phonocardiogram (PCG) of the heart sounds, a LED-photodiode pair to detect the photoplethysmogram (PPG) of the blood flow wave, a -controller, a wireless communication module and the power supply. With the proposed device no active participation would be required from human subjects for BP measurements, since the HR and the PAT are continuously extracted from the PCG and PPG signals. Dedicated signal processing algorithms were developed and implemented off-line to extract both HR and PAT. A subject-specific calibration protocol of the BP model was designed and implemented. The calibration and validation of the apparatus were performed on a cohort of 20 healthy subjects. A GIMA ABPM pressure Holter was chosen as reference device, and 8 measurements points, evenly distributed over a 10-minute interval, were used for model calibration for each subject. The range of DBP and SBP measurements were 52-85 mmHg and 90-141 mmHg, respectively. The results from Bland-Altman analysis showed that the mean±1.96SD for the estimated diastolic, systolic, and mean BP with the proposed method against reference were 0.01±7.55, 1.47±3.76, 0.74±4.38 mmHg, respectively. The corresponding mean absolute differences (MAD) were 3.06, 1.83, and 1.80 mmHg. These results demonstrates that the acquisition apparatus is able to continuously estimate the BP with an accuracy comparable to traditional cuff-based devices
Ex Vivo Evaluation of a Pressure-Sensitive Device to Aid Big Bubble Intrastromal Dissection in Deep Anterior Lamellar Keratoplasty
Full text linkPURPOSE: To develop and perform ex vivo testing for a device designed for semiquantitative determination of intracorneal dissection depth during big bubble (BB) deep anterior lamellar keratoplasty. METHODS: A prototype device connected to a syringe and cannula was designed to determine depth of intrastromal placement based on air rebound pressure emitted by a software controlled generator. Ex vivo testing of the device was conducted on human corneas mounted on an artificial anterior chamber in three experiments: (1) cannula purposely introduced at different depths measured with anterior segment optical coherence tomography, (2) cannula introduced as per the BB technique, and (3) simulation of the BB technique guided by the device. RESULTS: A positive pressure differential and successful BB were observed only when the cannula was positioned within 150 microns from the endothelial plane. In all successful BB cases (21/40), a repeatable increase in tissue rebound pressure was detected, which was not recorded in unsuccessful cases. The device was able to signal to the surgeon correct placement of the cannula (successful BB) in 16 of 17 cases and incorrect placement of the cannula (unsuccessful BB) in 8 of 8 cases (94.1% sensitivity, 100% specificity). CONCLUSIONS: In our ex vivo model, this novel medical device could reliably signal cannula positioning in the deep stroma for effective pneumatic dissection and possibly aid technical execution of BB deep anterior lamellar keratoplasty. TRANSLATIONAL RELEVANCE: A medical device that standardizes big bubble deep anterior lamellar keratoplasty could increase the overall success rate of the surgical procedure and aid popularization of deep anterior lamellar keratoplasty
A Novel Wearable Apparatus to Measure Fingertip Forces in Manipulation Tasks Based on MEMS Barometric Sensors
No full textArtificial tactile sensing is a challenging research topic in robotics, motor control, and rehabilitation engineering encompassing multi-disciplinary skills and different technologies. This paper presents the development of a wearable tactile thimble system using MEMS barometric sensors and flexible printed circuit board. Barometric sensors were carefully processed to make them able to transduce contact forces. Thumb, index, and medium fingers were equipped with an array of six sensing elements each, covering the central, lateral, and medial aspects of the fingertip. The sensor integration, signal read-out and processing, hardware architecture of the device, along with the calibration protocol, were described. The test results showed adequate sensitivity at very low forces with an almost linear transduction range up to about 4N (RMSE: 0.04N). Tests on object manipulation tasks highlighted the value of the proposed system demonstrating the ability of measuring both the force amplitude and contact points, demonstrating the suitability of barometric sensors for tactile applications
Measurement of electrical impedance in different ex-vivo tissues
No full textBioimpedance allows living tissues characterization and detection of pathological states. Although in previous years several methods have been proposed to assess bioimpedance, many instruments used in studies of living tissues characterization are commercial devices designed for the measurement of components or electronic circuits and therefore the measurement of biological tissues can be affected by electrical polarization. In order to test if electrical impedance spectroscopy may be helpful in providing further information about the structure and the properties of tissues, an impedance meter for living-tissues, able to avoid polarization, was developed. Subsequently, ex-vivo impedance measurements were performed by placing a needle-probe into 6 tissues (heart, kidney, lung, muscle, liver and fat) of 3 rabbits. Impedance was analyzed in terms of modulus and phase. In the range 2-10 kHz, considering both modulus and phase, it was possible to discriminate each tissue with statistical significance. In the lower considered range of frequencies (i.e., 10-100 Hz and 200-1000 Hz) this was not always the case. We conclude that the detailed analysis of modulus and phase in the frequency range of 2-10 kHz, by using an ad-hoc device able to avoid electrical polarization, allows to discriminate between several healthy living tissues
In-Vivo Measurements of Tissue Impeditivity by Electrical Impedance Spectroscopy
No full textThe electrical properties of biological tissues differ depending on their structural characteristics. In literature, a lot of study have been carried out with the intent of taking advantage of bioimpedance analysis. Unfortunately, many apparatuses used during these campaigns were not always designed for measurements on living tissues. As a consequence, data could be affected by electrode polarization. In 2016, we presented a new impedance meter, developed for measurements on living tissues. Initially, it was tested only on ex-vivo rabbit’s tissues with promising results. As a continuation, this device has been tested on in-vivo samples by placing a needle-probe into 3 tissues (liver, spleen, ovary) of 2 female dogs. Furthermore, was evaluated also the bioimpedance signal of the ovary explanted, comparing it with the in-vivo data. Bioimpedance was analyzed in terms of modulus and phase along a broad spectrum of frequencies (10Hz – 10kHz).
Data obtained confirm the possibility of discriminating among the 3 tested tissues, at high frequencies for modulus and at low for phase. Confirmation that values on in-vivo and ex-vivo tissues are comparable if detected within few minutes after the explant, is also reported. We conclude that this clinical evaluation confirmed, also in-vivo, the good performance of the device previously tested on ex-vivo tissues, and provide more information about the tissue properties and characteristics
Effect of lung resection on pleuro-pulmonary mechanics and fluid balance
No full textThe aim of the study was to determine in human patients the effect of lung resection on lung compliance and on pleuro-pulmonary fluid balance. Pre and post-operative values of compliance were measured in anesthetized patients undergoing resection for lung cancer (N=11) through double-lumen bronchial intubation. Lung compliance was measured for 10-12cmH2O increase in alveolar pressure from 5cmH2O PEEP in control and repeated after resection. No air leak was assessed and pleural fluid was collected during hospital stay. A significant negative correlation (r2=0.68) was found between compliance at 10min and resected mass. Based on the pre-operative estimated lung weight, the decrease in compliance following lung resection exceeded by 10-15% that expected from resected mass. Significant negative relationships were found by relating pleural fluid drainage flow to the remaining lung mass and to post-operative lung compliance. Following lung re-expansion, data suggest a causative relationship between the decrease in compliance and the perturbation in pleuro-pulmonary fluid balance
Experimental model to evaluate the effect of hydrothorax and lobar resection on lung compliance
Full text linkThe objective of this study was to evaluate to what extent lung compliance is affected by the individual and combined action of lung resection and hydrothorax in an animal model.Anaesthetized and mechanically ventilated rabbits (weight range 2÷2.2 kg) were randomized in two groups: (i) experimental hydrothorax (from 2 to 8 ml) (n = 5) and (ii) right lower lobe lobectomy (n = 4) and right middle plus lower lobe resection (n = 2). To obtain lung compliance, we measured alveolar, oesophageal pressures and lung volume during slow inflation manoeuvres in control conditions and after hydrothorax or lung resection. Lung compliance was estimated as the change in lung volume divided by the change in transpulmonary pressure. Based on the changes in compliance of the whole lung, we calculated the corresponding changes in compliance of the right lung, which was directly exposed to unilateral hydrothorax and lobectomy.Average total lung compliance in the control was 3.3 ± 0.8 (SD) ml/cmH2O. Eight millilitres of hydrothorax significantly decreased (P < 0.001) lung compliance to 2.7 ± 0.7 ml/cmH2O and increased pleural liquid pressure at the bottom of the cavity from -1 cmH2O up to ∼2.5-3 cmH2O. Resection of the right lower lobe significantly decreased (P < 0.001) lung compliance to 1.75 ± 0.3 ml/cmH2O. Resection of the right middle plus lower lobes significantly decreased (P < 0.001) lung compliance to 1.52 ± 0.4 ml/cmH2O.Following hydrothorax, the decrease in right lung compliance (∼45%) was much greater than that expected based on the estimated decrease in right lung volume (20%). We attribute this difference to the fact that hydrothorax causes the lung to be exposed to positive, rather than sub-atmospheric, pressure, causing atelectasis. Following lobectomy, right lung compliance decreased by 62 and 80% for estimated decreases in lung volume of 30 and 60%. This difference could reflect inaccuracy in the estimate of lung volume reduction based on resected weight and/or surgical damage. We conclude that potential detrimental effects of hydrothorax and lobar resection decrease lung compliance and expose the lung to the risk of over-distension when a chest drain is applied
- …
