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Exploration of novel self-powered gas sensors free of external energy supply restrictions, such as light illumination and mechanical vibration, for flexible and wearable applications is in urgent need. Herein, this work constructs a flexible and self-powered NO2 gas sensor based on zinc-air batteries (ZABs) with the cathode of the ZABs also acting as the gas-sensitive layer. Furthermore, the SiO2 coating film, serving as a hydrophobic layer, increases the three-phase interfaces for the NO2 reduction reaction. The constructed sensors exhibit a high sensing response (0.3 V @ 5 ppm), an ultralow detection limit (61 ppb), a fast sensing process (129 and 103 s), and excellent selectivity. Moreover, the sensors also possess a wide working temperature range and a low working temperature tolerance (0.34 V at -15 °C). Simulations indicate that the hydrophobic surface at the cathode-hydrogel interface will accommodate more NO2 gas molecules at the reaction sites and prevent the influence of inner water evaporation and direct dissolution of NO2 in the electrolyte, which is beneficial to the enhanced gas sensing abilities. Finally, the self-powered sensing device is incorporated into a smart sensing system for practical applications. This work will pave a new insight into the construction of integrated and energy self-sufficient smart gas sensing systems.
RESUMO
OBJECTIVE: To explore the predictive value of sequential organ failure assessment (SOFA) score combined the acute gastrointestinal injury (AGI) grading system in critical elderly patients with sepsis. METHODS: A retrospective analysis was conducted. Elderly patients with sepsis aged > 60 years admitted to medical intensive care unit (MICU) of General Hospital of Guangzhou Military Command from March 2014 to December 2015 and experiencing critical care over 48 hours were enrolled. Age, gender, acute physiology and chronic health evaluation II (APACHE II) score, sequential organ failure assessment (SOFA) score and AGI score at admission (SOFAinitial, AGIinitial), the highest SOFA score and AGI score within the first week (SOFAmax, AGImax), serum procalcitonin (PCT), C-reactive protein (CRP), albumin (ALB), platelet (PLT), hemoglobin (Hb) and lactate (Lac) levels, length of ICU stay, usage of mechanical ventilation and renal replacement therapy were recorded. The primary end point was 28-day mortality. To extract factors affecting 28-day mortality, the risk factor of death of the senile sepsis patients were analyzed by binary logistic regression analysis (stepwise method). Fitness of the model was assessed by the Hosmer-Lemeshow test and calibration plot (P > 0.05). Receiver operating characteristic (ROC) analysis was performed for APACHE II score, SOFAinitial score, SOFAmax score, AGIinitial score, AGImax score and SOFAmax and combined AGImax score. RESULTS: Ninety-one patients were enrolled, the incidence of AGI in elderly patients with sepsis was 100%; 34 patients died 28 days after the admission, and the 28-day mortality rate was 37.4%. Non-survivors presented a higher APACHE II score, SOFAinitial score, SOFAmax score, AGIinitial score, AGImax score and longer usage of mechanical ventilation and renal replacement therapy. SOFAmax score [odds ratio (OR) = 1.576] and AGImax score (OR = 5.695) were associated with 28-day mortality in binary logistic regression analysis (both P < 0.01). The area under the curve (AUC) and 95% confidence interval (95%CI) of SOFAmax score combined AGImax score was significantly higher than that of SOFAinitial score, SOFAmax score, AGIinitial score, AGImax score and APACHE II score [0.806 (0.710-0.881) vs. 0.723 (0.619-0.812), 0.786 (0.688-0.865), 0.641 (0.533-0.739), 0.633 (0.526-0.881), 0.638 (0.531-0.736), all P < 0.05]. The Youden index (55.37) and positive predict value (5.51) of SOFAmax score combined AGImax score were the largest. When its cut-off value reached 14, the sensitivity and specificity was 67.65% and 87.72%, respectively. According to score of APACHE II, SOFAinitial, SOFAmax or AGImax, the higher of each score, the higher mortality rate could be. CONCLUSIONS: The combination of SOFAmax score and AGImaxscore enable accurate prediction in elderly patients with sepsis.
