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ObjectiveTo investigate the feasibility of using pulse oximetry plethysmographic waveform (POP) to identify the restoration of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR).Methods An observational research was conducted. A porcine model of ventricular fibrillation (VF) arrest was reproduced. After 3 minutes of untreated VF, animals received CPR according to the latest CPR guidelines, providing chest compressions to a depth of 5 cm with a rate of 105 compressions per minute and instantaneous mechanical ventilation. After 2 minutes of CPR, animals were defibrillated with 100 J biphasic, followed by continuous chest compressions. Data of hemodynamic parameters, partial pressure of end-tidal carbon dioxide (PETCO2) and POP were collected. The change in POP was observed, and the characteristics of changes of the waves were recorded during the peri-CPR period using the time and frequency domain methods.Results VF was successfully induced in 6 pigs, except 1 death in anesthesia induction period.① After VF, invasive blood pressure waveform and POP of the animals disappeared. PETCO2 was (18.83±2.71) mmHg (1 mmHg=0.133 kPa), and diastolic arterial pressure was (23.83±5.49) mmHg in compression stage. Animals attained ROSC within 1 minute after defibrillation, with PETCO2 [(51.83±9.35) mmHg] and diastolic arterial pressure [(100.67±10.97) mmHg] elevated significantly compared with that of compression stage (t1 = 8.737,t2 = 25.860, bothP = 0.000), with appearance of arterial blood pressure waveform.② Characteristic changes in POP were found in all experimental animals. During the stages of induced VF, compression, ROSC, and compression termination, POP showed characteristic waveform changes. POP showed disappearance of waveform, regular compression wave, fluctuation hybrid and stable pulse wave in time domain method; while in the frequency domain method waveform disappearance, single peak of compression, double or fusion peak and single peak of pulse were observed.Conclusion Analysis of POP using time and frequency domain methods could not only quickly detect cardiac arrest, but also show a role as a feasible, non-invasive marker of ROSC during CPR.
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Objective In the treatment of tumor with high intensity focused ultrasound (HIFU),the acoustic pressure distribution determines the safety and reliability of HIFU.It is necessary to predict the acoustic field produced by HIFU transducer.Methods To analyze the acoustic pressure distribution of HIFU generated by different excitation frequency and variable incentive power,comparison was made between the acoustic pressure simulated by finite difference time domain (FDTD) method and the ones measured by experiments.ResultsThe resultsshowed that the pressureat focalpoint increasedwiththe increasing of excitation power,while the change in the focal length was negligible.The focal point moved towards the transducer with the frequency increasing until the maximum sound pressure was gained at the resonant frequency (RF).Conclusion The simulation results are consistent with the experiment results,indicating that the acoustic fields can be predicted by simulation.