【关键词】 exhaled,tidal,volume;neonates;ventilator;variation
breath-to-breath variability in displayed tidal volume:real or artifact?
correspondence to shabih manzar, md,division of neonatology,rockford memorial hospital,2400 north rockton avenue,rockford,illinois 61103,us
tel:+815- 971- 6500fax:+815-968-5742e-mail: shabihman@hotmail.com
［abstract］objectiveto study the breath to breath variability in the exhaled tidal volume (vte) measurements in surfactant treated mechanically ventilated premature neonates. methodsa group of surfactant treated extremely low birth weight infants (birth weight less than 1 000 grams) were selected. they were all mechanically ventilated using aveatm ventilator. the vte was measured by the low dead space, single-use pneumotachometer placed between the endotracheal tube and y-piece of the respiratory circuit. computer-assisted recordings were used to study the variation in vte measurements. the mean, median, range, variance, standard error of the mean (sem), standard deviation (sd) and 95% confidence interval (ci) were calculated for a given five-minute epoch. resultsthe mean vte for all mandatory breath was noted to be (6.3 ± 1.3) ml/kg while for spontaneous breath was (4.3 ± 2) ml/kg,p= 0.32. a low variance, low sd, low range, low 95% ci and low sem was noted for the five minutes epoch of vte measurements. conclusionsbedside tidal volume measurements vary widely on the second to second display. however, reliable measurements could be obtained by taking the average vte of five minutes period.
［key words］exhaled tidal volume;neonates;ventilator;variation
introduction
with the advent of new generation computer-assisted ventilators, pulmonary mechanics monitoring (pmm) is being increasingly used in the neonatal intensive care units ［1,2］.among the variety of pmm provided as a built-in feature, tidal volume is most often used parameter to assess the ventilation adequacy and to monitor pulmonary dynamics ［3~7］. tidal volume (vt) is defined as the volume of each breath for the entire respiratory cycle ［4］. in clinical settings, exhaled tidal volume (vte) is generally used as a substitute of vt. in neonates, vte is preferred over the measurements of inhaled tidal volume (vti) due to the fact that leak around the uncuffed endotracheal tube (used exclusively in neonates) is recognized to occur predominantly during inspiration ［5,6］.
