It is critical to maintain a relatively normal inspiratory effort during pressure support ventilation (PSV), the support level should be adjusted to match the patient's inspiratory effort. The inspiratory muscle pressure index (PMI) can reflect the elastic work of the respiratory system at the end of inspiration and has a significant correlation with inspiratory effort, and it has the outgoing advantages of being non-invasive and easy to obtain. Previous studies on PMI were based on physiological research and experimental conditions (PMIref), which require special pressure monitoring devices and software to collect and measure airway pressure. If PMI is going to be used in clinical practice, it is necessary to find a simple measurement method of PMI to replace PMIref. Most ventilators have airway pressure monitoring and end-inspiratory holding functions, and PMI can be measured by freezing the ventilator screen (PMIvent). The overall aim of this study was to determine PMIvent's clinical feasibility and validity for accessing inspiratory effort during PSV.
None
age younger than 18 years old or older than 85 years
known pregnancy and parturient
chronic occlusive pulmonary diseases
gastric, esophageal injury
Single group
pressure support level
Procedure/SurgeryBaseline ventilators were set by the principle of keeping VT/PBW at 6-8ml/kg and RR at 20-30 breaths/min and the decision of the responsible ICU physician. After then the fraction of inspired oxygen (FiO2), positive expiratory end pressure (PEEP), trigger sensitivity, and cycle-off criteria remain unchanged. Downward PS level titration was performed from 20 cmH2O to 2 cmH2O at a 2cm H2O interval. Every PS level was maintained for 20 minutes and then three end-inspiratory holdings (2-3seconds) and three end-expiratory holdings were performed. To avoid additional injury to the lung and diaphragm, the airway peak pressure (Ppeak) was limited to 30cmH2O.Inspiratory effort is measured as pressure generated by inspiratory muscles using esophageal pressure monitoring.
Agreement of PMIvent and PMIref
The accuracy of PMIvent compared to PMIref was assessed by a Bland-Altman plot for each ventilator.
Correlation of inspiratory effort and PMIvent
The inspiratory effort is measured as the pressure generated by inspiratory muscles using esophageal pressure monitoring. This study selected Pmus and PTPes per minute as the reference for inspiratory effort.
The predicted value of PMIvent for low/high effort
The target range for "high" inspiratory effort was defined as Pmus \> 10 cmH2O and PTPes per minute \> 200 cmH2O·s·min-1, and the target range for "low" inspiratory effort was defined as Pmus \< 5 cmH2O and PTPes per minute \< 50 cmH2O·s·min-1.
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Jian-Xin Zhou
Lead sponsor
Capital Medical University
Sponsor institution
