Microprocessor-based system for measurement of electrical impedances during haemodialysis and in postoperative care

The paper describes an instrument designed for accurate measurement of the mean specific electrical impedance of tissue. Two basic measurements are possible. One implementation called tetrapolar impedance plethysmography is employed for investigation with respect to transcellular fluid shifts during haemodialysis. The other measuring configuration called differential tetrapolar impedance plethysmography, deals with measurement of intrathoracic fluid content, which is important in monitoring treatment and prevention of lung oedema. An alternating current of 1 mA is passed through the tissue at different frequencies. Two measuring channels are available for differential tetrapolar measurement. Only one channel is required for straightforward tetrapolar measurement. Recovery of the impedance signals is achieved by synchronous demodulation. The impedance signal is passed through an analogue-to-digital convertor for digital processing to estimate the specific impedance in case of a differential tetrapolar measurement. Output display is possible via an xy recorder. The design of the instrument is discussed and some results shown.     

Simple parametrizations of maximum expiratory flow-volume curves

Summary Four elementary mono-compartmental lung models yield parametrizations of Maximal Expiratory Flow-Volume curves of normal subjects. The respective analytical functions are fitted to the measured curves and the mathematically derived ventilation indices are compared with standard measured data. While individual values of resistance and compliance seem devoid of a simple physical interpretation, their product indeed matches the models.     

Electronic device for the recording of isopressure-flow-volume (i.p.f.v.) curves

An electronic device for the automatic recording of isopressure-flow-volume (i.p.f.v.) curves was developed using a modified version of the flow interrupter technique. Following an inspiration up to total lung capacity, the subject made an expiratory effort against a closed shutter until the mouth pressure reached a given preset level between 5 and 50 cmH₂O, at which time the shutter reopened. Expiratory flow was sampled immediately after the shutter opening. When the volume reached a level, previously adjusted to correspond to one-tenth of vital capacity, the shutter closed again. The subject made a renewed effort against the closed shutter and the whole procedure was repeated from the initial condition until the expiration terminated at the residual volume. As the sampled flow and expired volume were plotted on an X-Y plotter with the aid of an electronic circuit in parallel with to the progress of the forced expiration, a flow-volume curve at an isopressure was thus described in ten steps. I.P.F.V. curves were measured in eight normal subjects and fifteen patients with various pulmonary diseases and the practical interpretation of these curves is discussed.     

Spirometric and flow-volume curve analysis in rats,and optimal parameters for estimating obstructive impairment

We obtained flow-volume (F-V) curves in anesthetized rats by applying positive pressure on the body surface. To obtain the best curve, tracheal intubation with either a 12 or 13 gauge catheter and a surface pressure greater than 56 cmH₂O was necessary. Peak expiratory flow rate (PEFR) and forced vital capacity (FVC) were shown to be optimal parameters for estimation of bronchoconstriction induced by methacholine inhalation while FEV_0.05 (forced expiratory volume at 0.05 s) and FEV_0.10 were of limited usefulness for this purpose. The descending segment of the F-V curve consisted of two or three phases, with later phases shortened during bronchoconstriction. In conclusion, PEFR and FVC are optimal parameters for estimation of bronchoconstriction in rats. The decreases in PEFR and FVC may reflect constriction in large and smaller airways, respectively.     

Effect of expiratory resistive loading on inspiratory and expiratory muscle fatigue

Inspiratory and expiratory pressures are increased during expiratory resistive loading (ERL). We asked whether ERL elicits inspiratory as well as expiratory muscle fatigue. On four separate days, seven male subjects underwent ERL to task failure. Subjects maintained respiratory frequency at 15 breaths min⁻¹, expiratory gastric pressure at 40% or 60% of maximum, and expiratory duty cycle at 0.4 or 0.7 (ERL_40%0.4, ERL_40%0.7, ERL_60%0.4, ERL_60%0.7). Inspiratory and abdominal muscle contractility was assessed before and up to 30 min after ERL by measuring transdiaphragmatic twitch pressure (P_di,tw) and gastric twitch pressure (P_ga,tw) in response to magnetic nerve stimulation. After each trial, P_di,tw and P_ga,tw were reduced below baseline values (−9 to −15% for P_di,tw and −15 to −22% for P_ga,tw; P < 0.05). The severity of diaphragm fatigue was unaffected by expiratory pressure production or expiratory duty cycle, whereas extending the expiratory duty cycle increased the severity of abdominal muscle fatigue. In conclusion, ERL elicits contractile fatigue of the diaphragm and the abdominal muscles.     

Estimation of the equilibrium constant for an antibody using data derived from an antiserum dilution curve

An equation is derived from the Law of Mass Action which enables the equilibrium constant of an antibody to be calculated directly from data obtained from an antiserum dilution curve. A graphical solution is obtained and examples using theoretically derived and experimental data are given.     

Value of the cumulative sum test for the assessment of a learning curve: Application to the introduction of patient-specific instrumentation for total knee arthroplasty in an academic department

Background

The purpose of the study was to use the cumulative summation (CUSUM) test to assess the learning curve during the introduction of a new surgical technique (patient-specific instrumentation) in total knee arthroplasty (TKA) in an academic department.

Multiplex PCR system for the rapid diagnosis of respiratory virus infection: systematic review and meta-analysis

ObjectivesTo provide a summary of evidence for the diagnostic accuracies of three multiplex PCR systems (mPCRs)—BioFire FilmArray RP (FilmArray), Nanosphere Verigene RV+ test (Verigene RV+) and Hologic Gen-Probe Prodesse assays—on the detection of viral respiratory infections.MethodsA comprehensive search up to 1 July 2017 was conducted on Medline and Embase for studies that utilized FilmArray, Verigene RV+ and Prodesse for diagnosis of viral respiratory infections. A summary of diagnostic accuracies for the following five viruses were calculated: influenza A virus (FluA), influenza B virus, respiratory syncytial virus, human metapneumovirus and adenovirus. Hierarchical summary receiver operating curves were used for estimating the viral detection performance per assay.ResultsTwenty studies of 5510 patient samples were eligible for analysis. Multiplex PCRs demonstrated high diagnostic accuracy, with area under the receiver operating characteristic curve (AUROC) equal to or more than 0.98 for all the above viruses except for adenovirus (AUROC 0.89). FilmArray, Verigene RV+ and ProFlu+ (the only Prodesse assay with enough data) demonstrated a summary sensitivity for FluA of 0.911 (95% confidence interval, 0.848–0.949), 0.949 (95% confidence interval, 0.882–0.979) and 0.954 (95% confidence interval, 0.871–0.985), respectively. The three mPCRs were comparable in terms of detection of FluA.ConclusionsPoint estimates calculated from eligible studies showed that the three mPCRs (FilmArray, Verigene RV+ and ProFlu+) are highly accurate and may provide important diagnostic information for early identification of respiratory virus infections. In patients with low pretest probability for FluA, these three mPCRs can predict a low possibility of infection and may justify withholding empirical antiviral treatments.     

Microprocessor-based system for spike and eye-movement data acquisition and storage

A simple system for simultaneous recording of eye position and spike activity during on-line experimentation is described. The system is based on a relatively inexpensive and widely distributed personal computer. While the hardware is configured from commercially available products, the software has been developed in our laboratory. Data acquisition is controlled by a few routines whose logic is outlined, together with the main limitations and the possible improvements of the system itself.     

Evaluation of PCR and high-resolution melt curve analysis for differentiation of Salmonella isolates

Consumption of poultry products contaminated with Salmonella is one of the major causes of foodborne diseases worldwide and therefore detection and differentiation of Salmonella spp. in poultry is important. In this study, oligonucleotide primers were designed from hemD gene and a PCR followed by high-resolution melt (HRM) curve analysis was developed for rapid differentiation of Salmonella isolates. Amplicons of 228?bp were generated from 16 different Salmonella reference strains and from 65 clinical field isolates mainly from poultry farms. HRM curve analysis of the amplicons differentiated Salmonella isolates and analysis of the nucleotide sequence of the amplicons from selected isolates revealed that each melting curve profile was related to a unique DNA sequence. The relationship between reference strains and tested specimens was also evaluated using a mathematical model without visual interpretation of HRM curves. In addition, the potential of the PCR–HRM curve analysis was evaluated for genotyping of additional Salmonella isolates from different avian species. The findings indicate that PCR followed by HRM curve analysis provides a rapid and robust technique for genotyping of Salmonella isolates to determine the serovar/serotype.     

超声心动图对冠心病诊断的特异性、敏感性和ROC曲线分析

目的: 对超声心动图诊断冠心病的特异性、敏感性和ROC曲线进行分析,评价其诊断价值。方法: 对114例临床诊断标准为冠心病的患者进行超声心动图检查,观察有无室壁运动异常及其部位,并测量左室射血分数、左室舒张末期内径、左室收缩末期内径、二尖瓣舒张早期峰值流速(E)和舒张晚期峰值流速(A),计算E/A比值。上述患者进行冠脉造影检查,观察3支冠状动脉有无病变、狭窄及狭窄程度,狭窄≥50%诊断为冠心病。结果: 114例中经冠脉造影明确为冠心病患者96例。冠心病超声心动图表现为:节段性室壁运动减弱、消失或矛盾运动。超声心动图诊断冠心病的敏感性为79.2%,定位准确率为75.0%。以左室室壁运动评分≥4为截点,诊断冠心病的敏感性为82.2%,特异性为100%,ROC曲线下面积为0.95(0.89-0.98)。结论: 超声心动图是诊断冠心病首选的无创性诊断方法。利用室壁节段性运动评分诊断冠心病具有较高的特异性和敏感性。     

The influence of inspiratory and expiratory muscle training upon rowing performance

We investigated the effect of 4 week of inspiratory (IMT) or expiratory muscle training (EMT), as well as the effect of a subsequent 6 week period of combined IMT/EMT on rowing performance in club-level oarsmen. Seventeen male rowers were allocated to either an IMT (n = 10) or EMT (n = 7) group. The groups underwent a 4 week IMT or EMT program; after interim testing, both groups subsequently performed a 6 week program of combined IMT/EMT. Exercise performance and physiological responses to exercise were measured at 4 and 10 week during an incremental rowing ergometer ‘step-test’ and a 6 min all-out (6MAO) effort. Pressure threshold respiratory muscle training was undertaken at the 30 repetition maximum load (∼50% of the peak inspiratory and expiratory mouth pressure, P _Imax or P _Emax, respectively). P _Imax increased during the IMT phase of the training in the IMT group (26%, P < 0.001) and was accompanied by an improvement in mean power during the 6MAO (2.7%, P = 0.015). Despite an increase in P _Emax by the end of the intervention (31%, P = 0.03), the EMT group showed no significant changes in any performance parameters during either the ‘step-test’ or 6MAO. There were no significant changes in breathing pattern or the metabolic response to the 6MAO test in either group, but the IMT group showed a small decrease in HR (2–5%, P = 0.001). We conclude that there were no significant additional changes following combined IMT/EMT. IMT improved rowing performance, but EMT and subsequent combined IMT/EMT did not.