The measurement of airway dead space by the CO 2SMO Plus was reproducible over a 1-h period in children requiring mechanical ventilation, provided ventilatory parameters were constant throughout the study. Physiologic dead space values from the SBT-CO2 method were similar to those from Bohr-Enghoff equations. Airway dead space values from the SBT-CO 2 method were smaller than those from Bohr-Enghoff equations. No significant difference was observed with time. ResultsĪirway dead space measurement had a good reproducibility during the 1-h period, whatever the method used (intraclass correlation coefficient: 0.84 to 0.87).
The two methods for calculating airway dead space were compared by using two-tailed Student’s t-test and Bland-Altman analysis. Two-way analysis of variance was used to evaluate the relationships between time and measurements. Intrasubject reproducibility of measurements was evaluated by the intraclass correlation coefficient. At the end of the study period, arterial blood gas was sampled in order to calculate alveolar and physiologic dead space. Airway dead space was determined automatically (Novametrix Medical Systems, USA), and manually by Bohr- Enghoff equations using data obtained by SBT-CO 2. The single-breath CO 2 test (SBT-CO 2) was recorded using the CO 2SMO Plus from the mean of 30 ventilatory cycles during 1 h (at T0, T15, T30, T45, and T60). Thirty-two mechanically ventilated children (0.13–15.4 years) who were clinically stable.
University pediatric intensive care unit. To assess the reproducibility of respiratory dead space measurements in ventilated children.
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