Effects of Propofol on Respiratory Drive and Patient-ventilator Synchrony during Pressure Support Ventilation in Postoperative Patients： A Prospective Study

Background： Propofol is increasingly nsed during partial support mechanical ventilation such as pressure support ventilation （PSV） in postoperative patients. However breathing pattern, respiratory drive, and patient-ventilator synchrony are affected by the sedative used and the sedation depth. The present study aimed to evaluate the physiologic effects of varying depths ofpropofbl sedation oll respiratory drive and patient-ventilator synchrony during PSV in postoperative patients. Methods： Eight postoperative patients receiving PSV for 〈24 h were enrolled. Propofol was administered to achieve and maintain a Ramsay score of 4, and the inspiratory pressure support was titrated to obtain a tidal volume （VT） of 6-8 ml/kg. Then, tile propolbl dose was reduced to achieve and maintain a Ramsay score of 3 and then 2. At each Ramsay level, the patient underwent 30-rain trials of PSV. We measured the electrical activity of the diaphragm, flow, airway presstlre, neuro-ventilatory efficiency （NVE）, and patient-ventilator synchrony. Results： Increasing the depth of sedation reduced the peak and mean electrical activity of the diaphragm, which suggested a decrease in respiratory drive, while VT remained unchanged. The NVE increased with an increase in the depth of sedation. Minute ventilation and inspiratory duty cycle decreased with an increase in the depth of sedation, but this only achieved statistical significance between Ramsay 2 and both Ramsay 4 and 3 （P 〈 0.05）. The ineffective triggering index increased with increasing sedation depth （9.5 -4- 4.0%, 6.7 - 2.0%, and 4.2-2.1% for Ramsay 4, 3, and 2, respectively） and achieved statistical significance between each pair of depth of sedation （P 〈 0.05）. The depth of sedation did not affect gas exchange. Conclusions： Propofol inhibits respiratory drive and deteriorates patient-ventilator synchrony to tile extent that varies with tile depth of sedation. Propolbl has less effect on breathing pattern and has no effect on VT and gas exchange in postoperative patients with PSV.

Neural control of pressure support ventilation improved patient-ventilator synchrony in patients with different respiratory system mechanical properties:a prospective,crossover trial

Background:Conventional pressure support ventilation(PSP)is triggered and cycled off by pneumatic signals such as flow.Patient-ventilator asynchrony is common during pressure support ventilation,thereby contributing to an increased inspiratory effort.Using diaphragm electrical activity,neurally controlled pressure support(PSN)could hypothetically eliminate the asynchrony and reduce inspiratory effort.The purpose of this study was to compare the differences between PSN and PSP in terms of patient-ventilator synchrony,inspiratory effort,and breathing pattern.Methods:Eight post-operative patients without respiratory system comorbidity,eight patients with acute respiratory distress syndrome(ARDS)and obvious restrictive acute respiratory failure(ARF),and eight patients with chronic obstructive pulmonary disease(COPD)and mixed restrictive and obstructive ARF were enrolled.Patient-ventilator interactions were analyzed with macro asynchronies(ineffective,double,and auto triggering),micro asynchronies(inspiratory trigger delay,premature,and late cycling),and the total asynchrony index(AI).Inspiratory efforts for triggering and total inspiration were analyzed.Results:Total AI of PSN was consistently lower than that of PSP in COPD(3%vs.93%,P=0.012 for 100%support level;8%vs.104%,P=0.012 for 150%support level),ARDS(8%vs.29%,P=0.012 for 100%support level;16%vs.41%,P=0.017 for 150%support level),and post-operative patients(21%vs.35%,P=0.012 for 100%support level;15%vs.50%,P=0.017 for 150%support level).Improved support levels from 100%to 150%statistically increased total AI during PSP but not during PSN in patients with COPD or ARDS.Patients’inspiratory efforts for triggering and total inspiration were significantly lower during PSN than during PSP in patients with COPD or ARDS under both support levels(P<0.05).There was no difference in breathing patterns between PSN and PSP.Conclusions:PSN improves patient-ventilator synchrony and generates a respiratory pattern similar to PSP independently of any level of support in patients with different respiratory system mechanical properties.PSN,which reduces the trigger and total patient’s inspiratory effort in patients with COPD or ARDS,might be an alternative mode for PSP.Trial Registration:ClinicalTrials.gov,NCT01979627;https://clinicaltrials.gov/ct2/show/record/NCT01979627.

Mechanical ventilation strategy for pulmonary rehabilitation based on patient-ventilator interaction

Mechanical ventilation is an effective medical means in the treatment of patients with critically ill,COVID-19 and other pulmonary diseases.During the mechanical ventilation and the weaning process,the conduct of pulmonary rehabilitation is essential for the patients to improve the spontaneous breathing ability and to avoid the weakness of respiratory muscles and other pulmonary functional trauma.However,inappropriate mechanical ventilation strategies for pulmonary rehabilitation often result in weaning difficulties and other ventilator complications.In this article,the mechanical ventilation strategies for pulmonary rehabilitation are studied based on the analysis of patient-ventilator interaction.A pneumatic model of the mechanical ventilation system is established to determine the mathematical relationship among the pressure,the volumetric flow,and the tidal volume.Each ventilation cycle is divided into four phases according to the different respiratory characteristics of patients,namely,the triggering phase,the inhalation phase,the switching phase,and the exhalation phase.The control parameters of the ventilator are adjusted by analyzing the interaction between the patient and the ventilator at different phases.A novel fuzzy control method of the ventilator support pressure is proposed in the pressure support ventilation mode.According to the fuzzy rules in this research,the plateau pressure can be obtained by the trigger sensitivity and the patient’s inspiratory effort.An experiment prototype of the ventilator is established to verify the accuracy of the pneumatic model and the validity of the mechanical ventilation strategies proposed in this article.In addition,through the discussion of the patient-ventilator asynchrony,the strategies for mechanical ventilation can be adjusted accordingly.The results of this research are meaningful for the clinical operation of mechanical ventilation.Besides,these results provide a theoretical basis for the future research on the intelligent control of ventilator and the automation of weaning process.

Respiratory evaluation of patients requiring ventilator support due to acute respiratory failure

This review, based on relevant published evidence and the authors` clinical experience, presents how to evaluate a patient with acute respiratory failure requiring ventilatory support. This patient must be carefully evaluated by nurses, physiotherapists, respiratory care practitioners and physicians regarding the elucidation of the cause of the acute episode of respiratory failure by means of physical examination with the measurement of respiratory parameters and assessment of arterial blood gases analysis to make a correct respiratory diagnosis. After the initial evaluation, the patient must quickly receive adequate oxygen and ventilatory support that has to be carefully monitored until its discontinuation. When available, a noninvasive ventilation trial must be done in patients presenting desaturation during oxygen mask and or PaCO2 retention, especially in cases of cardiogenic pulmonary edema and severe exacerbation of chronic obstructive pulmonary disease. In cases of noninvasive ventilation trial-failure, endotracheal intubation and invasive protective mechanical ventilation must be promptly initiated. In severe ARDS patients, low tidal ventilation, higher PEEP levels, prone positioning and recruitment maneuvers with adequate PEEP titration should be used. Recently, new modes of ventilation should allow a better patient-ventilator interaction or synchrony permitting a sufficient unloading of respiratory muscles and increase patient comfort. Patients with chronic obstructive pulmonary disease may be considered for a trial for early extubation to noninvasive positive pressure ventilation in centers with extensive experience in noninvasive positive pressure ventilation.