The impact of endotracheal tube's resistance on the respiratory systolic variation test / 中国医师进修杂志

ABSTRACT

Objective To study the effect of endotracheal tube's resistance on the respiratory systolic variation test(RSVT).Methods The RSVT,a test to predict fluid responsiveness was performed in 20 patients.The test consisted of the delivery of three congecutive pressure-controlled breaths with incremental peak inspiratory pressures of 10,20 and 30 cm H2O(1 cm H2O=0.098 kPa).The minimal values of the systolic arterial pressure following each of these three breaths were measured and plotted against their respective airway pressures,producing the RSVT slope.RSVT slope were compared between normal airway resistance and increased resistance circumstances,and the latter was simulated by advancing a Cooperdech bronchial blocker into endotracheal tube.Results Under normal resistance,RSVT slope was(0.39±0.21) volumes were(461.5±95.9),(891.5±149.8)and(1207.5±159.1)ml,when peak inspiratory pressures of 10,20 and 30 cm H2O were dehvered.When bronchial blocker was advanced into endotrecheal tube, (0.27±0.17)mm Hg,cm H2O significantly(P<0.01),and tidal volumes decreased to(434.5±92.8), (796.5±96.6)and(1097.5±68.4)ml(P<0.05 or<0.01).Conclusion Changes in endotraeheal tube's resistance can distort the RSVT slope.