Superimposed Perfect Binary Array-Aided Channel Estimation for OTFS Systems.

Orthogonal time-frequency space (OTFS) modulation outperforms orthogonal frequency-division multiplexing in high-mobility scenarios through better channel estimation. Current superimposed pilot (SP)-based channel estimation improves the spectral efficiency (SE) when compared to that of the traditional embedded pilot (EP) method. However, it requires an additional non-superimposed EP delay-Doppler frame to estimate the delay-Doppler taps for the following SP-aided frames. To handle this problem, we propose a channel estimation method with high SE, which superimposes the perfect binary array (PBA) on data symbols as the pilot. Utilizing the perfect autocorrelation of PBA, channel estimation is performed based on a linear search to find the correlation peaks, which include both delay-Doppler tap information and complex channel gain in the same superimposed PBA frame. Furthermore, the optimal power ratio of the PBA is then derived by maximizing the signal-to-interference-plus-noise ratio (SINR) to optimize the SE of the proposed system. The simulation results demonstrate that the proposed method can achieve a similar channel estimation performance to the existing EP method while significantly improving the SE.

Multiplex polymerase chain reaction detection enhancement of bacteremia and fungemia.

OBJECTIVE: To test a multiplex real-time polymerase chain reaction (PCR) method for simultaneous detection of multiple organisms in bloodstream infections. METHODS: Prospective observational study at the University of California Davis Medical Center (Sacramento, CA). Two hundred adult (>18 yrs) patients from the emergency room, intensive care units, and general medicine wards at risk of a bloodstream infection and who manifested signs of systemic inflammatory response syndrome (SIRS). Whole blood samples for PCR testing were collected at the same time as blood culture (BC). PCR results were compared to blood and other culture results. RESULTS: PCR detected potentially significant bacteria and fungi in 45 cases compared to 37 by BC. PCR detected the methicillin resistance (mecA) gene in all three culture-confirmed methicillin-resistant Staphylococcus aureus cases. More than 68% of PCR results were confirmed by blood, urine, and catheter culture. Independent clinical arbitrators could not rule out the potential clinical significance of organism(s) detected by PCR, but not by BC. PCR did not detect Enterococcus faecalis in five BC-confirmed cases. On average, seven patient samples could be tested simultaneously with the PCR method in 6.54 +/- .27 hrs. CONCLUSIONS: Multiplex PCR detected potentially significant bacteria and fungi that were not found by BC. BC found organisms that were not detected by PCR. Despite limitations of both BC and PCR methods, PCR could serve as an adjunct to current culture methods to facilitate early detection of bloodstream infections. Early detection of microorganisms has the potential to facilitate evidence-based treatment decisions, antimicrobial selection, and adequacy of antimicrobial therapy.

Validation of oxygen saturation measurements in a canine model of hemoglobin-based oxygen carrier infusion.

This study was designed to validate oxygen saturation measurements from the NOVA CO-Oximeter (NOVA Biomedical Corporation, Waltham, MA), the i-STAT System (Sensor Devices, Waukesha, WI), and the Corning 170 blood gas analyzer (Bayer Corporation, East Walpole, MA) under conditions similar to the clinical application of a hemoglobin-based oxygen carrier (HBOC, hemoglobin glutamer-200 [bovine]; Oxyglobin, Biopure Corporation, Cambridge, MA). A canine model was used for both in vitro and in vivo experiments. In vivo experiments were conducted in a canine laboratory, and in vitro experiments were conducted in a tonometry laboratory. Study subjects were six mixed-breed dogs, each weighing approximately 30 kg. In the first set of experiments, the target blood po(2) levels were reached by tonometry. In the second set of experiments, quantitative measurements of total oxygen content with the LEXO2CON-K (HOSPEX Fiberoptics, Chestnut Hill, MA) were performed, immediately followed by measurements with the NOVA CO-Oximeter and the i-STAT system. HBOC was added in concentrations of 16.2, 32.5, 65, and 97.5 g/L. To analyze the clinical significance of the differences in the results obtained with the each investigated instrument, blood samples from dogs treated with HBOC after acute hemorrhagic shock were used. Oxygen saturation, oxygen content, and po(2) were measured. There was a strong correlation between the oxygen saturation values measured with the investigated instruments in samples after tonometry and known po(2). The total calculated oxygen content varied by 5% based on results generated by calculations using the investigated instruments. The results did not change with different oxygenation of the sample. The differences among methods were not significant when the HBOC concentration was 16.2 g/L. Higher concentrations of HBOC increased the difference between calculated and measured oxygen content; the i-STAT system demonstrated a greater deviation compared with the results of the other two instruments. Systemic oxygen uptake using the investigated instruments showed a high correlation with values based on LEXO2CON-K measurements (R = 0.97 for CO-Oximeter, R = 0.96 for Corning 170 blood gas analyzer, and R = 0.79 for i-STAT system). Systemic oxygen uptake values based on CO-Oximeter and Corning 170 blood gas analyzer data showed 75% accuracy; i-STAT system accuracy was 63% for control samples and 50% for samples after HBOC infusion.

Oxygen saturation measurements in canine blood containing hemoglobin glutamer-200 (Bovine): in vitro validation of the NOVA CO-Oximeter.

This study was designed to validate in vitro oxygen saturation (SO2) measurements with the NOVA CO-Oximeter (Nova Biomedical Corp, Waltham, Mass, USA) in canine blood containing hemoglobin (Hb) glutamer-200 bovine (Hb-200; Oxyglobin, Biopure, Cambridge, Mass, USA) as a Hb-based oxygen carrier recently introduced into clinical practice. In the first set of experiments, stored blood from 6 mixed-breed canine blood donors was used. Target PO2 levels were reached in aliquots of blood samples by tonometry. Oxygen saturation was then measured with the test device and calculated based on known PO2 values. In the second set of experiments, total oxygen content was directly measured by means of an oxygen-specific electrode in aliquots of fresh whole arterial, venous, and mixed (arterial-venous) blood withdrawn from the same canine blood donors. Hb-200 was added to those blood samples to yield plasma Hb concentrations of 1.62, 3.25, 6.50, and 9.75 g/dL. Based on Hb content and SO2 measured by the NOVA CO-Oximeter in these samples, total oxygen content was also calculated for each sample and compared with measured values. A strong correlation was found between SO2 values measured with the co-oximeter in samples after tonometry, and calculated SO2 based on known PO2. Directly measured total blood O2 content varied by

Does lead interfere with hemoglobin-based oxygen carrier (HBOC) function? A pilot study of lead concentrations in three approved or tested HBOCs and oxyhemoglobin dissociation with HBOCs and/or bovine blood with varying lead concentrations.

UNLABELLED: We measured lead concentrations in three hemoglobin-based oxygen carriers (HBOCs; Oxyglobin, Hemopure, and Hemolink) and compared them with lead concentrations from blood-bank blood. Oxyhemoglobin dissociation was measured with large concentrations of lead in bovine HBOC, with or without bovine blood, and in bovine blood. Samples of each were prepared by combining one with normal saline (control), the second with small lead concentrations (22 micro g/dL), and the third with toxic lead concentrations (70 micro g/dL). They were blended in 2 tonometers at oxygen concentrations (2.5%, 5%, 8%, 10%, 21%, and 95%) with 5% CO(2) and the remainder nitrogen for 5 min per sample after a 15-min wash-in with each level of oxygen and were measured with co-oximetry. Oxygen saturation was plotted against PO(2), fitting fourth-order polynomial nonlinear regression to the data. The lead concentrations of the three HBOCs were 0.51, 0.22, 0.40 micro g/dL. There were no clinically important differences of the oxyhemoglobin dissociation curves as a function of lead concentration. The lead concentrations of the three tested HBOCs were small and no larger than the average for blood-bank blood. The presence of increasing concentrations of lead in either concentrated solution of bovine HBOC or a 1:1 mixture of bovine HBOC and native bovine blood does not appear to affect hemoglobin oxygenation in an acute in vitro model of increased lead concentrations. IMPLICATIONS: Gunshot wounds rapidly increase circulating lead concentrations. Lead concentrations are small in three hemoglobin-based oxygen carriers (HBOCs), and HBOCs and/or bovine blood do not appear to be affected by lead concentrations in terms of immediate oxygen on-loading and off-loading. HBOCs may be useful in patients with gunshot wounds.