Light-Responsive Actuator of Azobenzene-Containing Main-Chain Liquid Crystal Elastomers with Allyl Sulfide Dynamic Exchangeable Linkages.

Herein, a light-responsive and light-induced bond-exchange-reaction (BER)-capable actuator of the monodomain liquid crystal elastomer (xMLCEazo), developed using main-chain mesogenic oligomers containing azobenzene and allyl sulfide linkages, is investigated. Large quantities of the azobenzene and allyl dithiol linkages are incorporated into the main-chain mesogenic oligomer prepared via thiol-acrylate Michael addition polymerization (TAMAP). The xMLCEazo film is generated via visible-light-induced BER of the drawn polydomain xLCEazo (xPLCEazo) film prepared via TAMAP of tetrathiol cross-linkers and diacrylate-terminated mesogenic oligomers. The xMLCEazo film exhibits large length actuation (38%) through the photothermal effect, along with excellent self-healing and reprogramming properties, under ultraviolet (UV) light irradiation. UV light induced BER of the xMLCEazo film is used to develop complex-shaped actuators with a bilayer film, containing the xMLCEazo and xPLCEazo films, which are bonded by the UV light induced BER without glue. The individual arm of the complex eight-arm flower is remotely actuated under UV light irradiation, and a circular band is rolled under blue laser light irradiation, demonstrating the local remote-controlled actuation and fuel-free motion of the motile soft robot using light irradiation, respectively. Thus, the xMLCEazo film can be expanded to other interesting applications requiring reprogrammable, self-healing, reprocessable, patternable, and remote-controlled light-triggered elastic, rubber-like actuators.

Electrospun Rubber Nanofiber Web-Based Dry Electrodes for Biopotential Monitoring.

This study aims to find base materials for dry electrode fabrication with high accuracy and without reducing electrode performance for long-term bioelectric potential monitoring after electroless silver plating. Most applications of dry electrodes that have been developed in the past few decades are restricted by low accuracy compared to commercial Ag/AgCl gel electrodes, as in our previous study of PVDF-based dry electrodes. In a recent study, however, nanoweb-based chlorinated polyisoprene (CPI) and poly(styrene-b-butadiene-b-styrene) (SBS) rubber were selected as promising candidates due to their excellent elastic properties, as well as their nanofibril nature, which may improve electrode durability and skin contact. The electroless silver plating technique was employed to coat the nanofiber web with silver, and silver nanoweb(AgNW)-based dry electrodes were fabricated. The key electrode properties (contact impedance, step response, and noise characteristics) for AgNW dry electrodes were investigated thoroughly using agar phantoms. The dry electrodes were subsequently tested on human subjects to establish their realistic performance in terms of ECG, EMG monitoring, and electrical impedance tomography (EIT) measurements. The experimental results demonstrated that the AgNW dry electrodes, particularly the SBS-AgNW dry electrodes, performed similarly to commercial Ag/AgCl gel electrodes and were outperformed in terms of long-term stability.

Respiration monitoring in PACU using ventilation and gas exchange parameters.

The importance of perioperative respiration monitoring is highlighted by high incidences of postoperative respiratory complications unrelated to the original disease. The objectives of this pilot study were to (1) simultaneously acquire respiration rate (RR), tidal volume (TV), minute ventilation (MV), SpO2 and PETCO2 from patients in post-anesthesia care unit (PACU) and (2) identify a practical continuous respiration monitoring method by analyzing the acquired data in terms of their ability and reliability in assessing a patient's respiratory status. Thirteen non-intubated patients completed this observational study. A portable electrical impedance tomography (EIT) device was used to acquire RREIT, TV and MV, while PETCO2, RRCap and SpO2 were measured by a Capnostream35. Hypoventilation and respiratory events, e.g., apnea and hypopnea, could be detected reliably using RREIT, TV and MV. PETCO2 and SpO2 provided the gas exchange information, but were unable to detect hypoventilation in a timely fashion. Although SpO2 was stable, the sidestream capnography using the oronasal cannula was often unstable and produced fluctuating PETCO2 values. The coefficient of determination (R2) value between RREIT and RRCap was 0.65 with a percentage error of 52.5%. Based on our results, we identified RR, TV, MV and SpO2 as a set of respiratory parameters for robust continuous respiration monitoring of non-intubated patients. Such a respiration monitor with both ventilation and gas exchange parameters would be reliable and could be useful not only for respiration monitoring, but in making PACU discharge decisions and adjusting opioid dosage on general hospital floor. Future studies are needed to evaluate the potential clinical utility of such an integrated respiration monitor.

Tissue Characterization Using an Electrical Bioimpedance Spectroscopy-Based Multi-Electrode Probe to Screen for Cervical Intraepithelial Neoplasia.

The successful management of cervical intraepithelial neoplasia (CIN) with proper screening and treatment methods could prevent cervical cancer progression. We propose a bioimpedance spectroscopic measurement device and a multi-electrode probe as an independent screening tool for CIN. To evaluate the performance of this screening method, we enrolled 123 patients, including 69 patients with suspected CIN and 54 control patients without cervical dysplasia who underwent a hysterectomy for benign disease (non-CIN). Following conization, the electrical properties of the excised cervical tissue were characterized using an electrical bioimpedance spectroscopy-based multi-electrode probe. Twenty-eight multifrequency voltages were collected through the two concentric array electrodes via a sensitivity-optimized measurement protocol based on an electrical energy concentration method. The electrical properties of the CIN and non-CIN groups were compared with the results of the pathology reports. Reconstructed resistivity tended to decrease in the CIN and non-CIN groups as frequency increased. Reconstructed resistivity from 625 Hz to 50 kHz differed significantly between the CIN and non-CIN groups (p < 0.001). Using 100 kHz as the reference, the difference between the CIN and non-CIN groups was significant. Based on the difference in reconstructed resistivity between 100 kHz and the other frequencies, this method had a sensitivity of 94.3%, a specificity of 84%, and an accuracy of 90% in CIN screening. The feasibility of noninvasive CIN screening was confirmed through the difference in the frequency spectra evaluated in the excised tissue using the electrical bioimpedance spectroscopy-based multi-electrode screening probe.

Noninvasive, simultaneous, and continuous measurements of stroke volume and tidal volume using EIT: feasibility study of animal experiments.

Currently, there is no noninvasive method available for simultaneous measurements of tidal volume and stroke volume. Electrical impedance tomography (EIT) has been used for regional lung ventilation imaging. Cardiac EIT imaging, however, has not been successful due to the technical difficulty in extracting weak cardiogenic components. Instead of regional imaging, in this paper, we use the EIT technique to simultaneously measure two global variables of tidal volume and stroke volume. Time-varying patterns of boundary voltage data originating from lung ventilation and cardiac blood flow were extracted from measured boundary voltage data using the principal component analysis (PCA) and independent component analysis (ICA). The source consistency theory was adopted to separately synthesize time-series of boundary voltage data associated with lung ventilation and cardiac blood flow. The respiratory volume signal (RVS) and cardiac volume signal (CVS) were extracted from reconstructed time-difference EIT images of lung ventilation and cardiac blood flow, respectively. After calibrating the volume signals using the mechanical ventilator and the invasive transpulmonary thermodilution (TPTD) method, tidal volume and stroke volume were computed as valley-to-peak values of the RVS and CVS, respectively. The difference in the tidal volume data between EIT and mechanical ventilator was within ± 20 ml from six pigs. The difference in the stroke volume data between EIT and TPTD was within ± 4.7 ml from the same animals. The results show the feasibility of the proposed method as a new noninvasive cardiopulmonary monitoring tool for simultaneous continuous measurements of stroke volume and tidal volume that are two most important vital signs.

[Clinical significance of incidentally detected eosinophilic esophagitis with pathologic review].

BACKGROUND/AIMS: Eosinophilic esophagitis (EE) is a chronic inflammatory disorder characterized by abnormal dense eosinophilic infiltration of esophageal mucosa and results in dysphasia and food impaction. EE is being increasingly recognized in adults. The prevalence is largely unknown. This study was performed to evaluate the detection rate of EE diagnosed based on pathologic criteria and to define the clinical characteristics of EE in Korea. METHODS: We reviewed biopsy specimen of the 1,609 patients who underwent esophageal biopsy from January 2006 till August 2008. The presence of more than 20 eosinophils per high power field in biopsy specimens was considered cases of EE. Clinical information and endoscopic findings were obtained. RESULTS: 7 (0.4%) patients were diagnosed as EE based on pathologic criteria retrospectively. Clinical symptoms were epigastric pain (43%), regurgitation (29%), dyspepsia (14%), and no symptom (14%). Endoscopic findings were whitish exudates or granules (57%), esophageal polyp (29%), and hyperemic change (14%). Two patients received treatment. One patient with bronchial asthma improved after treatment with inhaled corticosteroid, and one patient improved after 8 week proton pump inhibitor therapy. CONCLUSIONS: Eosinophilic esophagitis was found in 0.4% of the total esophageal biopsied cases. Our results suggest that Korean patients with eosinophilic esophagitis showed symptoms mimicking gastroesophageal reflux disease and atypical endoscopic findings. Therefore, regardless of the gross appearance of the mucosa, meticulous diagnostic approaches are needed for patients with swallowing difficulty and lack of response to proton pump inhibitor.

[Clinical analysis of recurrence rate and symptom improvement in gastro-esophageal reflux disease patients].

BACKGROUND/AIMS: Gastro-esophageal reflux disease (GERD) is a chronic condition, with 50-80% of patients experiencing recurrence within one year following completion of initial treatment. The present study aimed to estimate recurrence rate and treatment response in GERD patients treated with proton pump inhibitor. METHODS: A total of 207 symptomatic GERD patients, which were confirmed by endoscopy from July 2008 till January 2009, were enrolled. They were divided into non-erosive reflux disease (NERD) group and erosive reflux disease (ERD) group by endoscopic findings. Patients were treated with lansoprazole 15 mg (NERD group) or 30 mg (ERD group) once daily for 8 weeks. The presence of symptoms was assessed in each patient at baseline and post-treatment using a questionnaire. Subsequent symptomatic recurrence on the cessation of therapy in each improved patients was checked by telephone survey or outpatient interview. RESULTS: Ninety-four patients and 113 patients were first diagnosed with NERD and ERD, respectively. The mean post-treatment follow-up period was 24.4+/-8.5 weeks. Recurrence rate was 40.0% (NERD, 43.8%; ERD, 37.1% (p=0.224)). Recurrence time was 10.1+/-5.8 weeks (NERD 9.6 weeks; ERD, 10.6 weeks (p=0.444)). Regarding the symptom improvement after 8 week therapy with lansoprazole, 89.4% (NERD, 85.1%; ERD, 92.9% (p=0.056)) of total patients were symptomatically improved. CONCLUSIONS: Forty percentage of GERD patients recurred within 6 months following the completion of 8 week therapy with lansoprazole. Recurrence rate, recurrence time, and rate of symptom improvement were not significantly different between NERD group treated with half dose and ERD group treated with full dose lansoprazole.