Accuracy of Mean Value of Central Venous Pressure from Monitor Digital Display: Influence of Amplitude of Central Venous Pressure during Respiration

Background A simple measurement of central venous pressure(CVP)-mean by the digital monitor display has become increasingly popular.However,the agreement between CVP-mean and CVP-end(a standard method of CVP measurement by analyzing the waveform at end-expiration)is not well determined.This study was designed to identify the relationship between CVP-mean and CVP-end in critically ill patients and to introduce a new parameter of CVP amplitude(ΔCVP=CVPmax-CVPmin)during the respiratory period to identify the agreement/disagreement between CVP-mean and CVP-end.Methods In total,291 patients were included in the study.CVP-mean and CVP-end were obtained simultaneously from each patient.CVP measurement difference(|CVP-mean-CVP-end|)was defined as the difference between CVP-mean and CVP-end.TheΔCVP was calculated as the difference between the peak(CVPmax)and the nadir value(CVPmin)during the respiratory cycle,which was automatically recorded on the monitor screen.Subjects with|CVP-mean-CVP-end|≥2 mm Hg were divided into the inconsistent group,while subjects with|CVP-mean-CVP-end|2 mm Hg were divided into the consistent group.ResultsΔCVP was significantly higher in the inconsistent group[7.17(2.77)vs.5.24(2.18),P0.001]than that in the consistent group.There was a significantly positive relationship betweenΔCVP and|CVP-mean-CVP-end|(r=0.283,P 0.0001).Bland-Altman plot showed the bias was-0.61 mm Hg with a wide 95%limit of agreement(-3.34,2.10)of CVP-end and CVP-mean.The area under the receiver operating characteristic curves(AUC)ofΔCVP for predicting|CVP-mean-CVP-end|≥2 mm Hg was 0.709.With a high diagnostic specificity,usingΔCVP3 to detect|CVP-mean-CVP-end|lower than 2mm Hg(consistent measurement)resulted in a sensitivity of 22.37%and a specificity of 93.06%.UsingΔCVP8 to detect|CVP-mean-CVPend|8 mm Hg(inconsistent measurement)resulted in a sensitivity of 31.94%and a specificity of 91.32%.Conclusions CVP-end and CVP-mean have statistical discrepancies in specific clinical scenarios.ΔCVP during the respiratory period is related to the variation of the two CVP methods.A highΔCVP indicates a poor agreement between these two methods,whereas a lowΔCVP indicates a good agreement between these two methods.

Damage evaluation of notched aluminum alloy and weld based on acoustic emission and digital image monitoring

Acoustic emission （ AE ） features during the fracture process of notched wrought aluminum alloy 7N01 and weld were investigated under the three-point bending load. Wavelet transform is used to investigate the time-frequency features of AE signals during the test. The experimental results showed that AE energy was effective indicators to detect the crack initiation for 7N01 aluminum. The digital images from monitoring the notch tip region of 7 NO1 aluminum sample verify the prediction of AE signals. The weld emits low energy, weak signal strength, and low peak amplitude, while stronger AE energy, amplitude, and more AE event counts for the base metal. In short, the AE technique was more sensitive to the changes in the fracture mode and could be used to monitor the damage development in welded structures.

Co-seismic changes of well water level and volume strain meter in capital area and its vicinity,due to the Nov.14,2001 Ms8.1 Kunlun Mountain earthquake,China

The Kunlunshan Mountain Ms8.1 earthquake, occurred in Nov.14, 2001, is the first event with magnitude more than 8 in the China earthquake monitoring history, specifically at the beginning of digital techniques in precursor monitoring networks. Any investigation of recorded data on this earthquake is very important for testing the operation of the digital monitoring networks and understanding the preparation, occurrence, and adjustment of stress/strain of strong continental earthquakes. In this paper we investigated the coseismic response changes of well water level of groundwater and volume strain meter of bore hole in digital earthquake monitoring network of Capital area and its vicinity, due to the Nov.14, 2001 Ms8.1 Kunlun Mountain earthquake. The responding time, shapes or manners, amplitudes, and lasting time of well water level and strain-meters to seismic wave are studied in comparison. Then we discussed the possibility that the response changes of groundwater to strong distant earthquakes can be understood as one kind of observing evidence of stress/strain changes induced by distant earthquake.

Automatic test system development for digital beam position monitor of HEPS and BEPCII

Purpose Hundreds of digital beam position monitor processors(DBPM)are required to be produced during the construction of projects such as High Energy Photon Source(HEPS)and the upgrade project of the Beijing Electron Positron Collider(BEPCII),which brings great challenges to the test work.In order to achieve accurate,fast,and complete mass production tests of DBPMs,an automatic test system(ATS)has been developed in this article.Methods According to the test items of DBPM,the standardized testing softwareflow is designed based on virtual instru-ment program control technology and experimental physics and industrial control system(EPICS),which realize automatic adjustment of test parameters and automatic acquisition of test result data.Results and conclusions The ATS can realize one-button testing of channel coefficients,channel linearity,attenuator linearity,beam current dependence(BCD)and sampling signal-to-noise ratio(SNR),and generate test reports.The total test time is less than 3 minutes,which is significantly more efficient compared to manual testing.More than 90 BEPCII DBPMs has been tested by this ATS in the lab.The test results proved that such a system could automatically recognize defective products and satisfy the requirements of mass testing.