Application and Nursing of Pulse Index Continuous Cardiac Output (PiCCO) Volume Monitoring in Early Fluid Resuscitation in Patients with Septic Shock

Background: Septic shock is a rapidly changing and fatal syndrome that can cause comprehensive deterioration of cardiopulmonary and renal function and multiple organ failure. At the same time, septic shock has the complex clinical manifestations and hemodynamics. PiCCO can accurately monitor blood flow, physical and volume indicators, and active and effective fluid resuscitation are important measures to reduce the fatality rate of septic shock and improve the prognosis of patients. Objectives: To explore the application and nursing of PiCCO in early fluid resuscitation in patients with septic shock. Methods: This was a retrospective observational study. The observation group and the control group each had 30 cases. The observation group used PiCCO to guide fluid resuscitation;the control group used conventional methods to guide fluid resuscitation. The changes in CVP, HR, MAP, and urine volume per hour were observed in the two groups. The changes of various indicators before and after fluid resuscitation, the length of stay in ICU and the mortality rate were compared between the two groups. All the outcomes were collected from the electronic medical case system after patients’ discharge from the hospital. Results: APACHE II, CVP, HR, MAP were compared between the observation group and the control group, and the differences were statistically significant (P < 0.05). The blood volume of patients in the observation group was significantly improved after fluid supplementation (P < 0.05). Compared with the control group, the length of stay in ICU in the observation group was significantly shorter, and the mortality rate was also significantly reduced (P < 0.05). Conclusion: PiCCO can be better used in early fluid resuscitation of patients with septic shock.

Spectral Calculation of the Output Voltage of an Inverter with Bipolar Pulse Width Modulation

Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for powering induction furnaces, in audio technique. Spectrum of signals sampled by pulse amplitude modulation and output voltage spectrum of the converter with pulse width modulation have similar properties. Spectrum of signals sampled by pulse amplitude modulation contains a harmonic of frequency equal to the frequency of the modulating signal and the harmonics of frequencies equal to the sum of frequency of the modulating signal and multiples of the sampling frequency. The output voltage spectrum of the converter with bipolar pulse width modulation contains harmonic of frequency equal to the frequency of the modulating signal and harmonics of frequencies equal to sum of the frequency of the modulating signal and multiples of the frequency of the carrier signal. It also contains harmonics of frequencies equal to the sum of the multiples of the frequency of the modulating signal and the multiples of the carrier signal. The comparison analysis was carried out for the harmonics of the output voltage of the converter with bipolar pulse width modulation in time domain. The dependency of the amplitudes and frequency spectrum on the wave forms of the carrier signal and modulating signal was shown. Similarity of the output voltage spectrum of the converter and signal spectrum sampled by the pulse width modulation was also shown. Key words： Output voltage converter with bipolar pulse width modulation, spectral analysis, Fourier series, carrier signal, reference signal.

Evaluation of respiratory dysfunction in a pig model of severe acute dichlorvos poisoning

Background Respiratory failure is the main cause of death in acute organophosphorus pesticide poisoning. In this study, a pulse-induced contour cardiac output monitor was used to evaluate the respiratory status in a pig model of acute dichlorvos poisoning. Methods Twenty female pigs were randomly allocated to dichlorvos （n=7）, atropine （n=7）, and control （n=6） groups. In the dichlorvos group, pigs were administered 80% emulsifiable dichlorvos （100 mg/kg） via a gastric tube. In the atropine group, pigs were similarly administered dichlorvos, and 0.5 hours later, atropine was injected to attain and maintain atropinization. The control group was administered saline solution. Arterial blood gas was measured at 0, 0.5, 1, 2, 4, and 6 hours post-injection. The extravascular lung water index and pulmonary vascular permeability index were recorded by the pulse-induced contour cardiac output monitor. At termination of the study, the animals were euthanized, the lung wet-to-dry weight ratio was determined, and histopathology was observed. Results In the dichlorvos group, the extravascular lung water index and pulmonary vascular permeability index were substantially increased from 0.5 hours and were particularly high within 1 hour. In the atropine group, these indices increased initially, but decreased from the 1-hour mark. The control group exhibited no obvious changes. In both the dichlorvos and atropine groups, the extravascular lung water index was negatively correlated with partial pressure of oxygen/fraction of inspiration oxygen （POz/FiO2） and positively correlated with the pulmonary vascular permeability index. Compared with the control group, the lung wet-to-dry weight ratio markedly increased and the histopathological findings obviously changed in the dichlorvos group, but only mildly increased and changed, respectively, in the atropine group. Conclusion The extravascular lung water index is an appropriate and valuable parameter for assessment of respiratory function in acute dichlorvos poisoning.