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Background : Many patients develop respiratory failure that need mechanical ventilator. The respiratory failure caused by different types of pathophysiology, New generation mechanical ventilators incorporate some new adjustment modes sophisticated to improve patientventilator interface by altering inspiratory flow pattern.
Objective : This study objective was to cteronstrate the respiratory mechanics is inspiratory waveform and peak inspiratory flow generated by the mechanical ventilators for different characteristics of lung models.
Method : THE PURITAN BENNETT 7200A was operated in control mode with constant setting of Vt*, RR*, FiO2*, Ppeak* Ppla*, MAP*, Vte* were repeatedly measured and Raw*, C’* were calculated for each three inspiratory flow waveform and three level of inspiratory flow rate under four simulated pathological condition : 1. low compliance lung model 2. high airway resistance lung model 3. mixed low compliance and high airway resistance lung model in comparison with 4. control lung model. The data were analyzed by ANOVA test.
Result : 1. Under ventilation of low compliance lung model, square waveform produced quite low Ppeak, Ppla compare with other waveform 2. Under ventilation of high airway resistance lung model, decelerated waveform produced lowest Ppeak and Ppla. (P < 0.05) 3. Under ventilation of mixed high airway resistance and very low compliance lung model, decelerated waveform produced lowest Ppeak and Ppla. (P < 0.05) 4. Under ventilation all type of lung medels decelerated waveform produced highest mean airway pressure. (p < 0.05)
Conclusion : Under ventilation of low compliance lung model, lower plateau pressure were often seen in square waveform. Under ventilation of high airway resistance lung model, decelerated waveform make lower in peak and plateau pressure. Under ventilation of all characteristic of lung model decelerated. The result of this study may guide to proper use of respirator adjustment in those condition.
*FiO2 = inspired oxygen concentration (%)
*RR = respiratory rate (time/min)
Keyword : Inspiratory flow pattern, Inspiratory waveform, square waveform, decelerated waveform, sine waveform lung model.
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