Influence of different respiratory mechanics properties on inspiratory flow index during pressure controlled ventilation

Abstract

Objective: To observe the influence of tidal volume(VT) variation on the inspiratory flow index during pressure controlled ventilation (PCV) in different lung models. Methods: The Hamilton C3 ventilator was connected to an ASL5000 lung simulator, which simulated lung mechanics in patients with healthy adult, patients with mild and severe chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS), and 4 respiratory mechani-cs models were constructed. mild and severe chronic obstructive pulmonary disease (COPD)The [system compliance (Crs) was 30.0 and 60.0 mL/cmH2O, the airway resistance (Raw) was 5.0, 10.0 and 20.0 cmH2O/(L•s)]. The Hamilton C3 ventilator was operated in PCV mode were actived with output VT at 5.0, 7.0 and 10.0 ml/kg, positive end-expiratory pressure (PEEP) was set at 5.0 cmH2O, breathing rate at 10 bpm, and inspiratory time was set at 3.0 sec. The performance characteristics were collected, and the inspiratory flow index and expiratory time constant(RCexp) were estimated by specical equationscalculated. Results: The flow index was not aboveless than 1.0 in all four lung mechanics profiles models during passive ventilation with PCV mode. Peak inspiratory flow (PIF), peak expiratory flow (PEF) and inspiratory driving pressure (DP) were increased gradually with the increment of tidal volume, whereas the flow index was decreased. There were the similar value in the estimation of The flow index in health adult and of the ARDS lung models was similar to that of healthy adults, but RCexp was significantly reduced in severe restrictive model. Flow index and end-inspiratory flow (EIF) were significantly higher in severe COPD model than in the other lung models, which with flow index was close toreaching 0.80 when VT was at 5.0 mL/kg. Conclusions: Flow index has the characteristics ofis an non-invasive derivative parameter and continuous can be monitoringed continuously, and is affected by the alteration of tidal volume and respiratory mechanical properties. During pressure controlled ventilation, the estimation continuous monitoring of flow index is useful to evaluate the severity of airflow limitation and the association between the patient’s inspiratory effort and ventilator outputted assistance level.

Keywords

• |pressure controlled ventilation|flow index|simulation|chronic obstructive pulmonary disease|acute respiratory distress syndrome