As an important medical electronic equipment for the cardioversion of malignant arrhythmia such as ventricular fibrillation and ventricular tachycardia, cardiac external defibrillators have been widely used in the clinics. However, the resuscitation success rate for these patients is still unsatisfied. In this paper, the recent advances of cardiac external defibrillation technologies is reviewed. The potential mechanism of defibrillation, the development of novel defibrillation waveform, the factors that may affect defibrillation outcome, the interaction between defibrillation waveform and ventricular fibrillation waveform, and the individualized patient-specific external defibrillation protocol are analyzed and summarized. We hope that this review can provide helpful reference for the optimization of external defibrillator design and the individualization of clinical application.
The dynamic electrocardiogram (ECG) collected by wearable devices is often corrupted by motion interference due to human activities. The frequency of the interference and the frequency of the ECG signal overlap with each other, which distorts and deforms the ECG signal, and then affects the accuracy of heart rate detection. In this paper, a heart rate detection method that using coarse graining technique was proposed. First, the ECG signal was preprocessed to remove the baseline drift and the high-frequency interference. Second, the motion-related high amplitude interference exceeding the preset threshold was suppressed by signal compression method. Third, the signal was coarse-grained by adaptive peak dilation and waveform reconstruction. Heart rate was calculated based on the frequency spectrum obtained from fast Fourier transformation. The performance of the method was compared with a wavelet transform based QRS feature extraction algorithm using ECG collected from 30 volunteers at rest and in different motion states. The results showed that the correlation coefficient between the calculated heart rate and the standard heart rate was 0.999, which was higher than the result of the wavelet transform method (r = 0.971). The accuracy of the proposed method was significantly higher than the wavelet transform method in all states, including resting (99.95% vs. 99.14%, P < 0.01), walking (100% vs. 97.26%, P < 0.01) and running (100% vs. 90.89%, P < 0.01). The absolute error [0 (0, 1) vs. 1 (0, 1), P < 0.05] and relative error [0 (0, 0.59) vs. 0.52 (0, 0.72), P < 0.05] of the proposed method were significantly lower than the wavelet transform method during running state. The method presented in this paper shows high accuracy and strong anti-interference ability, and is potentially used in wearable devices to realize real-time continuous heart rate monitoring in daily activities and exercise conditions.
ObjectiveTo systematically review the safety of low molecular weight heparin (LMWH) in pregnancy. MethodsPubMed, EMbase, The Cochrane Library, WanFang Data, VIP, and CNKI databases were electronically searched to collect randomized controlled trials (RCTs) and cohort studies on the safety of LMWH in pregnancy from inception to March 30th, 2020. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of included studies. Meta-analysis was then performed using RevMan 5.3 software. ResultsA total of 77 RCTs and 13 cohort studies were included. The results of meta-analysis showed that LMWH increased the incidence of postpartum hemorrhage (RR=1.50, 95%CI 1.00 to 2.25, P=0.05). However, there was no significant difference. The incidence of hematological adverse events was different from the results of RCTs and cohort studies. The results of RCT subgroup analysis showed that LMWH increased ecchymosis at the injection site (RR=1.60, 95%CI 1.24 to 2.08, P=0.000 4). However, the incidence of overall skin system adverse events did not increase significantly. LMWH reduced the incidence of cardiovascular adverse events (RR=0.18, 95%CI 0.07 to 0.46, P=0.000 3). LMWH failed to increase the occurrence of fetal congenital malformations, digestive system, central nervous system, skeletal system, and systemic adverse events. ConclusionsCurrent evidence suggests that LMWH is relatively safe to use during pregnancy. However, whether it increases postpartum hemorrhage and hematological adverse events is unclear. Due to limited quality and quantity of the included studies, more high-quality studies are required to verify the above conclusions.