Objective:To observe and analyze the effect of airflow obstruction on the inspiratory flow index and patient-ventilator synchronization in non-invasive pressure support ventilation (NI-PSV). Methods:The ASL 5000 machine simulation lung system was used to simulate health adult on semi-recumbent position and patients with chronic obstructive pulmonary disease (COPD),whose body weights were 70 kg. The models of health adult,mild obstruction,moderate obstruction and severe obstruction were set. The static compliance (Cst) of the simulated lung system was 60 mL/cmH2O,and the airway resistance (Raw) values of health adult,COPD patients with mild obstruction,moderate obstruction and severe obstruction model were respectively 5.0,10.0,15.0 and 20.0 cmH2O/(L*s),and the effort of spontaneous inhalation (Pmus) was 5.0 cmH2O,and the inspiratory time was 1.6s,and the respiratory rate was 15 times/min. Using the mode of spontaneous to time control (S/T) of Respironics V60 ventilator to operate,and the positive end-expiratory pressure (PEEP) was 5.0 cmH2O. The output tidal volume (VT) of ventilator was controlled at 7.0-8.0 mL/kg through adjusted the inspiratory pressure. The output various ventilation parameters and the change of breathing work of the simulated lung were collected,and the flow index was calculated. Results:Peak inspiratory flow (PIF) and peak expiratory flow (PEF) were decreased gradually with the severity of airflow obstruction of models of COPD patients,which inspiratory triggering flow (Flow-trig) was always remained at approximate 6.0 L/min. The value of flow index of the model with severe obstruction reached to 0.65,and the delay time (Td) of inspiratory triggering was more than 400 ms. The switching between inhalation and exhalation was from premature cycling (-469.50±16.35) ms of health adult model to mildly delayed cycling (207.25±14.86) ms,and the difference of that was significant (t=69.28,P<0.05). The inspiratory work of breathing (WOBpat) and ventilator work (WOBtot) of severe obstruction model of COPD patient were higher than those of health adults,and mild obstruction and moderate obstruction model of COPD patients,but the inspiratory work ratio (WOBpat/tot) of severe obstruction model of COPD patient was lower than that of other 3 kinds of models,and the differences were significant (F=2477.70,46960.87,51222.97,P<0.01),respectively. Conclusion:During NI-PSV support,airflow obstruction not only can decrease the value of peak airflow,change airflow shape and lead to increase the value of inspiratory flow index,but also can increase breathing work,thus affect patient-ventilator synchronization.
Pressure support ventilationFlow indexPatient-ventilator synchronizationChronic obstructive pulmonary disease (COPD)Noninvasive ventilation
维普
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