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Background: Enhancing venous return during cardiopulmonary resuscitation (CPR) can lead to better hemodynamics and improved outcome after cardiac arrest (CA). Peripheral Intravenous Analysis (PIVA) provides feedback on venous flow changes and may indicate an increase in venous return and cardiac output during CPR. We hypothesize PIVA can serve as an early indicator of increased venous return, preceding end-tidal CO2 (etCO2) increase, before the return of spontaneous circulation (ROSC) in a rat model of CA and CPR. Results: Eight male Wistar rats were intubated and ventilated, and etCO2 was measured. Vessels were cannulated in the tail vein, femoral vein, femoral artery, and central venous and connected to pressure transducers. Ventilation was discontinued to achieve asphyxial CA. After 8 min, CPR began with ventilation, epinephrine, and automated chest compressions 200 times per minute until mean arterial pressure increased to 120 mmHg. Waveforms were recorded and analyzed. PIVA was calculated using a Fourier transformation of venous waveforms. Data are mean ± SE. Maximum PIVA values occurred in the tail vein 34.7 ± 2.9 s before ROSC, with subsequent PIVA peaks in femoral vein and centrally at 30.9 ± 5.4 and 25.1 ± 5.0 s, respectively. All PIVA peaks preceded etCO2 increase (21.5 ± 3.2 s before ROSC). Conclusion: PIVA consistently detected venous pressure changes prior to changes in etCO2. This suggests that PIVA has the potential to serve as an important indicator of venous return and cardiac output during CPR, and also as a predictor of ROSC. [ABSTRACT FROM AUTHOR]

Ensuring tunnel linings’ quality is crucial for tunnel structures’ safety and long-term functionality. This study focuses on exploring tunnel lining quality detection technology based on the impulse echo acoustic method to enhance detection efficiency and accuracy. Initially, a series of tunnel lining samples are collected, and acoustic tests are conducted to obtain the acoustic characteristics of the lining materials. Subsequently, the impulse echo acoustic method is employed to detect the tunnel lining, followed by frequency spectrum analysis and waveform analysis of the acoustic signals. A comparison is made between the analyzed signals and simulated data or standard quality requirements. The proposed method involves the generation of impact on the lining and recording the resulting acoustic echo signal. Signal processing techniques and machine learning algorithms are applied to evaluate and classify the lining quality based on the distinctive features of the acoustic signals. Experimental results reveal that the tunnel lining quality detection technology achieves a remarkable accuracy rate of over 96% from the perspective of fine management. This approach enables the swift identification of defects, cracks, and damages in lining materials while providing quantitative quality assessment. The application potential of the tunnel lining quality detection technology based on the impulse echo acoustic method in fine management has been substantiated, as it effectively assesses the quality of tunnel linings and offers robust support for the safe operation of tunnels. [ABSTRACT FROM AUTHOR]

A split Hopkinson pressure bar apparatus driven by a pendulum hammer was used to perform uniaxial compression tests to examine the degradation process of green sandstone subjected to repetitive impact loading. The acoustic characteristics, dissipated energy, deformation characteristics, and microstructure evolution were investigated. The representative stress-strain curve can be broken into five stages that were characterized by changes in the axial strain response during impact loading. Both the ultrasonic wave velocity and cumulative dissipated energy exhibited obvious three-stage behavior with respect to the impact number. As the impact number increased, more than one peak was observed in the frequency spectra, and the relative weight of the peak frequency increased in the low-frequency range. According to the evolution of the ultrasonic wave velocity, the degradation process was divided into three stages. By comparing the intact stage I and early stage II microcrack development patterns, the initiation of new cracks and elongation of existing cracks were identified as the main degradation mechanisms. Furthermore, a slight increase in the number of cracks was observed, and microcrack lengths steadily increased. Moreover, due to the low level of microcrack damage, the deformation mechanism was mainly characterized by volume compression during impact loading. In late stage II, the main degradation mechanism was the elongation of existing cracks. Additionally, as microcracks accumulated in the rock samples, cracks were arranged parallel to the loading direction, which led to volume dilation. In stage III, microcracks continued to elongate nearly parallel to the loading direction and then linked to each other, which led to intense degradation in the rock samples. In this stage, rock sample deformation was mainly characterized by volume dilation during impact loading. Finally, rock samples were split into blocks with fractures oriented subparallel to the loading direction. These results can improve the understanding of the stability evaluations of rock structures subjected to repetitive impact loading. [ABSTRACT FROM AUTHOR]

Background: Recently, different software has been developed to automatically analyze multiple intracranial pressure (ICP) parameters, but the suggested methods are frequently complex and have no clinical correlation. The objective of this study was to assess the clinical value of a new morphological classification of the cerebrospinal fluid pulse pressure waveform (CSFPPW), comparing it to the elastance index (EI) and CSF-outflow resistance (R), and to test the efficacy of an automatic ICP analysis. Methods: An artificial neural network (ANN) was trained to classify 60 CSFPPWs in four different classes, according to their morphology, and its efficacy was compared to an expert examiner's classification. The morphology of CSFPPW, recorded in 60 patients at baseline, was compared to EI and R calculated at the end of an intraventricular infusion test to validate the utility of the proposed classification in patients' clinical evaluation. Results: The overall concordance in CSFPPW classification between the expert examiner and the ANN was 88.3 %. An elevation of EI was statistically related to morphological class' progression. All patients showing pathological baseline CSFPPW (class IV) revealed an alteration of CSF hydrodynamics at the end of their infusion test. Conclusions: The proposed morphological classification estimates the global ICP wave and its ability to reflect or predict an alteration in CSF hydrodynamics. An ANN can be trained to efficiently recognize four different CSF wave morphologies. This classification seems helpful and accurate for diagnostic use. [ABSTRACT FROM AUTHOR]

Abstract: The role of ventricular–arterial hemodynamic interaction in the occurrence of arterial dissection and rupture in vascular Ehlers–Danlos syndrome (vEDS) is unknown. We recently introduced an ultrasound-based method to extract, from common carotid artery (CCA) diameter waveforms, central arterial properties and left ventricular (LV) systolic time intervals. We obtained CCA diameters, compliance and distensibility coefficients, and LV isovolumic contraction and ejection periods (ICP and EP) of 19 vEDS patients (aged 27–65 yrs) and 19 age-matched healthy controls. CCA distension and compliance tended to be lower in vEDS subjects (p = 0.062 and p = 0.073), especially in younger patients. ICP (−12 ms) and EP (−24 ms) were shorter (p < 0.001), while heart rate was increased (+10 bpm; p < 0.001) in vEDS. The ICP/EP ratio and estimated isovolumic dP LV/dt indicated increased LV contractility in vEDS. In conclusion, vascular EDS patients tend to have a lower CCA compliance but a normal pulse pressure, most likely reflecting reduced physical fitness. [Copyright &y& Elsevier]

Central aortic blood pressure (BP), obtained from radial arterial waveform using the transfer function method (TFM), has been shown to have prognostic value independently of brachial BP. In this study, the relationship between peripheral systolic BP (SBP) and aortic SBP was evaluated. We further investigated whether TFM-derived aortic SBP can be estimated by information obtained from the radial waveform. The radial waveform was analysed to obtain the first peak of radial SBP (SBP1), second peak of radial SBP (SBP2), radial augmentation index (AI) (radial (SBP2−DBP)/(SBP1−DBP) × 100 and aortic SBP and AI using TFM in 233 subjects in the supine position. Measurements were repeated after changing position to the prone position. The constructed equation was validated in 149 community residents with different backgrounds. Radial SBP2 was closer to TFM-derived aortic SBP compared with brachial SBP. TFM-derived aortic SBP was approximated by the equation: aortic SBP=18.9—radial SBP2−0.03 × HR—0.214 × radial AI (r2=0.992). The equation was also applicable to predicting aortic SBP in the prone position as well as in different populations (mean difference between predicted aortic SBP and TFM-derived aortic SBP: −0.01±1.34 and 1.05±1.47 mm Hg, respectively). Radial arterial waveform analysis can be used for estimation of TFM-derived aortic SBP.Journal of Human Hypertension (2009) 23, 538–545; doi:10.1038/jhh.2008.154; published online 8 January 2009 [ABSTRACT FROM AUTHOR]

The arterial pulse at any site is created by an impulse generated by the left ventricle as it ejects blood into the aorta, together with multiple impulses travelling in the opposite direction from reflecting sites in the peripheral circulation. The compound wave at any site depends on the pattern of ventricular ejection, the properties of large arteries, particularly their stiffness (which determines rate of propagation) and the distance to and impedance mismatch at reflecting sites. Physicians are familiar with waveform analysis in the time domain, as in the electrocardiogram (ECG) where the principal features are explicable on the basis of atrial depolarisation followed by ventricular depolarisation, then repolarisation. Effects of cardiac functional and structural disease can be inferred from the ECG. It is more difficult to make similar interpretations from the pulse waveform and clinicians usually use this only to count heart rate, extremes of the pressure pulse to express systolic and diastolic pressure, and (sometimes) time from wave foot to incisural notch to measure time of systole and diastole. More information can be gleaned from the shape of the arterial pressure wave through consideration of the factors which create it—on stiffening of large arteries with age, effects of drugs on smallest arteries, and changes in such arterial properties on left ventricular load and function. Such is a major challenge to future physicians. It is aided by better and more accurate methods for measuring flow and diameter as well as pressure waveforms, and by appropriate use of other analytic techniques such as analysis of the pulse in the frequency domain. [ABSTRACT FROM AUTHOR]

Inter-crystalline pores, cavities, and fractures created from diagenetic shrinkage of dolomite are inter-connected each other, forming fine oil-and gas-bearing reservoirs. It is hard to predict these complex fracture-cavity reservoirs because of their random distribution, different growth timing, and so on. Taking the lacustrine dolomite fracture-pore reservoir in the Lower Cretaceous Xiagou Formation in the Qingxi oilfield within the Jiuquan basin as an example, we put forward a comprehensive geophysical method to predict carbonate fractures. [ABSTRACT FROM AUTHOR]

Summary Objective. Although intracranial hypertension is one of the important prognostic factors after head injury, increased intracranial pressure (ICP) may also be observed in patients with favourable outcome. We have studied whether the value of ICP monitoring can be augmented by indices describing cerebrovascular pressure-reactivity and pressure-volume compensatory reserve derived from ICP and arterial blood pressure (ABP) waveforms. Method. 96 patients with intracranial hypertension were studied retrospectively: 57 with fatal outcome and 39 with favourable outcome. ABP and ICP waveforms were recorded. Indices of cerebrovascular reactivity (PRx) and cerebrospinal compensatory reserve (RAP) were calculated as moving correlation coefficients between slow waves of ABP and ICP, and between slow waves of ICP pulse amplitude and mean ICP, respectively. The magnitude of ‘slow waves’ was derived using ICP low-pass spectral filtration. Results. The most significant difference was found in the magnitude of slow waves that was persistently higher in patients with a favourable outcome (p<0.00004). In patients who died ICP was significantly higher (p<0.0001) and cerebrovascular pressure-reactivity (described by PRx) was compromised (p<0.024). In the same patients, pressure-volume compensatory reserve showed a gradual deterioration over time with a sudden drop of RAP when ICP started to rise, suggesting an overlapping disruption of the vasomotor response. Conclusion. Indices derived from ICP waveform analysis can be helpful for the interpretation of progressive intracranial hypertension in patients after brain trauma. [ABSTRACT FROM AUTHOR]

We examine the initial subevent (ISE) of the M 6.7, 1994 Northridge, California, earthquake in order to discriminate between two end-member rupture initiation models: the ‘preslip’ and ‘cascade’ models. Final earthquake size may be predictable from an ISE's seismic signature in the preslip model but not in the cascade model. In the cascade model ISEs are simply small earthquakes that can be described as purely dynamic ruptures. In this model a large earthquake is triggered by smaller earthquakes; there is no size scaling between triggering and triggered events and a variety of stress transfer mechanisms are possible. Alternatively, in the preslip model, a large earthquake nucleates as an aseismically slipping patch in which the patch dimension grows and scales with the earthquake's ultimate size; the byproduct of this loading process is the ISE. In this model, the duration of the ISE signal scales with the ultimate size of the earthquake, suggesting that nucleation and earthquake size are determined by a more predictable, measurable, and organized process. To distinguish between these two end-member models we use short period seismograms recorded by the Southern California Seismic Network. We address questions regarding the similarity in hypocenter locations and focal mechanisms of the ISE and the mainshock. We also compare the ISE's waveform characteristics to those of small earthquakes and to the beginnings of earthquakes with a range of magnitudes. We find that the focal mechanisms of the ISE and mainshock are indistinguishable, and both events may have nucleated on and ruptured the same fault plane. These results satisfy the requirements for both models and thus do not discriminate between them. However, further tests show the ISE's waveform characteristics are similar to those of typical small earthquakes in the vicinity and more importantly, do not scale with the mainshock magnitude. These results are more consistent with the cascade model. [ABSTRACT FROM AUTHOR]

A new system for the online real-time waveform separation of the nerve impulses recorded from multichannel extracellular electrodes placed to the peripheral nerve trunk has been developed using two microprocessors and a graphics computer. One microprocessor (Intel 8085) performs nerve impulse detection and the other (Intel 8086) separates nerve impulses by clustering in the two-dimensional histograms representing the distribution of the parameters extracted from their waveforms. System performance was examined with two channel impulses recorded from the nerve trunk innervating the Sartorius muscle of a frog. These data could be classified into 6-8 different groups in real time. [ABSTRACT FROM AUTHOR]

The treatment of choice in progressive hydrocephalus is drainage of cerebrospinal fluid in order to reduce elevated intracranial pressure (ICP). Defining the right moment for surgical intervention, however, in a hydrocephalic infant on the basis of clinical signs alone can be a difficult task. Clinical signs of raised ICP are known to be unreliable and sometimes even misleading. In the present study, the relationship between long-term anterior fontanelle pressure (AFP) measurements and clinical signs was investigated in 37 infants with hydrocephalus. The decision as to whether to operate or not was based on clinical signs alone; AFP values were not taken into account. There was an overall difference between the non-operated group and the preoperative measurements in the operated group, and also between the preoperative and the postoperative measurements in the latter, in regard to both AFP measurements and clinical signs. Almost all preoperative AFP values were increased. The direct correlation (ϕ) between most individual clinical signs and AFP levels, however, was low (ϕ=0.15-0.41). The clinical sign 'tense fontanelle' showed the best correlation with the AFP levels (ϕ=0.75). Furthermore, using logistic regression analysis, no combination of clinical signs could be found which reliably predicted the AFP. The relationship between the AFP pressure variables and clinical signs was also examined. The pathological A-waves occurred only in the presence of raised (baseline) AFP, a situation in which considerably more frequent B-waves were observed as well. It was concluded that clinical signs of raised ICP in infantile hydrocephalus are not very reliable and AFP monitoring can therefore provide valuable information on intracranial dynamics in patients with dubious neurological manifestations of progressive hydrocephalus. [ABSTRACT FROM AUTHOR]

The authors have investigated the relationships between the amplitude of the ICP pulse wave, the mean values of ICP and CPP, and the outcome of 56 head injured ventilated patients. The ICP was monitored continuously using a Camino transducer (35 patients) or subdural catheter (21 patients). The mean Glasgow Coma Score was 6 (range 3-13; 5 patients had a GCS > 8 after resuscitation). Patients were grouped according to their Glasgow Outcome Score assessed at 12 months after injury. The amplitude of ICP pulse waveform was assessed using the fundamental harmonic of the pulse waveform (AMP) to avoid distortion caused by different frequency responses of the pressure transducers used in the study. Statistical analysis revealed that in patients with fatal outcome the ICP pulse amplitude increased when the mean ICP increased to 25 mmHg and then began to decrease. The upper breakpoint of the AMP-ICP relationship was not present in patients with good/moderate outcome. The moving correlation coefficient between the fundamental harmonic of ICP pulse wave and the mean ICP (RAP: R-symbol of correlation between A-amplitude and P-pressure) was introduced to describe the time-dependent changes in correlation between amplitude and mean ICP. The RAP was significantly lower in patients who died or remained in the vegetative state. In 7 patients who died from uncontrollable intracranial hypertension RAP was oscillating or decreased to 0 or negative values well before brain-stem herniation. The combination of an ICP above 20 mmHg for a period longer than 6 hours with low correlation between the amplitude and pressure (RAP < 0.5) was described as an predictive index of an unfavourable outcome. [ABSTRACT FROM AUTHOR]

Cerebrospinal dynamics has been investigated by statistical analysis of results of computerised monitoring of 80 head injured patients admitted to the Intensive Care Unit at Pinderfields General Hospital. One minute average values of intracranial pressure (ICP), systemic arterial pressure (ABP), cerebral perfusion pressure (CPP), amplitude of the fundamental component of the intracranial pressure pulse wave and the short-term moving correlation coefficient between that amplitude and mean ICP (RAP) were recorded. It was found that reduction of CPP down to 40mmHg was more often caused by decrease in ABP than increase in ICP. Further falls in CPP below 40mmHg were caused by substantial increases in ICP above 25 mmHg. The relationship between the ICP pulse wave amplitude and CPP showed a significant gradual increase in amplitude with CPP decreasing from 75 to 30 mmHg. For CPP below 30 mmHg there is a sharp decrease in amplitude followed by a change in the coefficient RAP from positive to negative values. This was interpreted as a sign of critical disturbance in cerebral circulation. [ABSTRACT FROM AUTHOR]

This is the second topical volume on 'Recent Advances in Nuclear Explosion Monitoring' that started with Pure and Applied Geophysics Topical Volume 167 (2010), and again reports on the most recent advances in science and technology that have been achieved to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). This progress in the development and testing of new sensor technologies and analysis methodologies in all relevant scientific disciplines improves the capabilities in detection, location and characterization of CTBT-relevant events. In particular, the latter poses a challenge for smaller events, where natural or manmade but CTBT-irrelevant sources can generate false-positive events. The efficient discrimination of these events pursued at a minimum risk of missing a nuclear explosion is the overall challenge. The 29 papers of this volume can be structured into 16 waveform studies, eight in the field of radionuclide monitoring and related atmospheric backtracking, and five papers related to on-site inspection or overhead detection of relevant events, with many of these originally presented at a special session on 'Research and Development in Nuclear Explosion Monitoring' at the most recent annual General Assemblies of the European Geosciences Union. [ABSTRACT FROM AUTHOR]

Analysis of cerebrospinal fluid pulse pressure was reported to be useful in the assessment of the cerebrospinal pressure-volume compensation. The method for the estimation of high-frequency centroid (HFC) was modified and used to verify the correlation between HFC and other compensatory parameters investigated by means of the lumbar infusion test in 94 hydrocephalic children. The results confirm that in hydrocephalus HFC is positively correlated to cerebrospinal elasticity coefficient, but inversely to mean CSF pressure and pulse wave amplitude. It was also demonstrated that HFC decreased dynamically during the infusion test. [ABSTRACT FROM AUTHOR]

Background: Femoral dP/dtmax (maximum rate of the arterial pressure increase during systole) measured by pulse contour analysis has been proposed as a surrogate of left ventricular (LV) dP/dtmax and as an estimator of LV systolic function. However, femoral dP/dtmax may be influenced by LV loading conditions. In this study, we evaluated the impact of variations of LV systolic function, preload and afterload on femoral dP/dtmax in critically ill patients with cardiovascular failure to ascertain its reliability as a marker of LV systolic function. Results: We performed a prospective observational study to evaluate changes in femoral dP/dtmax, thermodilution-derived variables (PiCCO2—Pulsion Medical Systems, Feldkirchen, Germany) and LV ejection fraction (LVEF) measured by transthoracic echocardiography during variations in dobutamine and norepinephrine doses and during volume expansion (VE) and passive leg raising (PLR). Correlations with arterial pulse and systolic pressure, effective arterial elastance, total arterial compliance and LVEF were also evaluated. In absolute values, femoral dP/dtmax deviated from baseline by 21% (201 ± 297 mmHg/s; p = 0.013) following variations in dobutamine dose (n = 17) and by 15% (177 ± 135 mmHg/s; p < 0.001) following norepinephrine dose changes (n = 29). Femoral dP/dtmax remained unchanged after VE and PLR (n = 24). Changes in femoral dP/dtmax were strongly correlated with changes in pulse pressure and systolic arterial pressure during dobutamine dose changes (R = 0.942 and 0.897, respectively), norepinephrine changes (R = 0.977 and 0.941, respectively) and VE or PLR (R = 0.924 and 0.897, respectively) (p < 0.05 in all cases). Changes in femoral dP/dtmax were correlated with changes in LVEF (R = 0.527) during dobutamine dose variations but also with effective arterial elastance and total arterial compliance in the norepinephrine group (R = 0.638 and R = − 0.689) (p < 0.05 in all cases). Conclusions: Pulse contour analysis-derived femoral dP/dtmax was not only influenced by LV systolic function but also and prominently by LV afterload and arterial waveform characteristics in patients with acute cardiovascular failure. These results suggest that femoral dP/dtmax calculated by pulse contour analysis is an unreliable estimate of LV systolic function during changes in LV afterload and arterial load by norepinephrine and directly linked to arterial waveform determinants. [ABSTRACT FROM AUTHOR]

Background: Femoral dP/dtmax (maximum rate of the arterial pressure increase during systole) measured by pulse contour analysis has been proposed as a surrogate of left ventricular (LV) dP/dtmax and as an estimator of LV systolic function. However, femoral dP/dtmax may be influenced by LV loading conditions. In this study, we evaluated the impact of variations of LV systolic function, preload and afterload on femoral dP/dtmax in critically ill patients with cardiovascular failure to ascertain its reliability as a marker of LV systolic function. Results: We performed a prospective observational study to evaluate changes in femoral dP/dtmax, thermodilution-derived variables (PiCCO2—Pulsion Medical Systems, Feldkirchen, Germany) and LV ejection fraction (LVEF) measured by transthoracic echocardiography during variations in dobutamine and norepinephrine doses and during volume expansion (VE) and passive leg raising (PLR). Correlations with arterial pulse and systolic pressure, effective arterial elastance, total arterial compliance and LVEF were also evaluated. In absolute values, femoral dP/dtmax deviated from baseline by 21% (201 ± 297 mmHg/s; p = 0.013) following variations in dobutamine dose (n = 17) and by 15% (177 ± 135 mmHg/s; p < 0.001) following norepinephrine dose changes (n = 29). Femoral dP/dtmax remained unchanged after VE and PLR (n = 24). Changes in femoral dP/dtmax were strongly correlated with changes in pulse pressure and systolic arterial pressure during dobutamine dose changes (R = 0.942 and 0.897, respectively), norepinephrine changes (R = 0.977 and 0.941, respectively) and VE or PLR (R = 0.924 and 0.897, respectively) (p < 0.05 in all cases). Changes in femoral dP/dtmax were correlated with changes in LVEF (R = 0.527) during dobutamine dose variations but also with effective arterial elastance and total arterial compliance in the norepinephrine group (R = 0.638 and R = − 0.689) (p < 0.05 in all cases). Conclusions: Pulse contour analysis-derived femoral dP/dtmax was not only influenced by LV systolic function but also and prominently by LV afterload and arterial waveform characteristics in patients with acute cardiovascular failure. These results suggest that femoral dP/dtmax calculated by pulse contour analysis is an unreliable estimate of LV systolic function during changes in LV afterload and arterial load by norepinephrine and directly linked to arterial waveform determinants. [ABSTRACT FROM AUTHOR]