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Zobel, J.
Vollumetric capnography and slope-CO2 in mechanically ventilated infants and children under the age of 36 months
Humanmedizin; [ Diplomarbeit ] Graz Medical University; 2015. pp. 114 [OPEN ACCESS]
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Authors Med Uni Graz:: Zobel Joachim
Advisor:: Eber Ernst
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Abstract:: Objectives: Volumetric capnography (VCAP) provides useful information about respiratory function in mechanically ventilated patients. Therefore VCAP-derived parameters could be used to calculate dead space fractions, and further on as prognostic factors in terms of the duration of mechanical ventilation and the mortality. In our study the main focus was on CO2-derived parameters (paCO2, petCO2, pACO2, pECO2, VCO2, pa-etCO2, and pa-ACO2), dead space fractions (VDalv/VT, VDphys/VT, VDaw/VT, VDBohr/VT), and slope-CO2. The aim of our study was to show the difference of those parameters in patients with short-term (< 48 hours) and long-term mechanical ventilation (= 48 hours), and further on over the course of time in Group B (= 48 hours). Furthermore, we wanted to show the correlation between certain parameters. Materials and methods: In our retrospective study we separately analysed the values of 51 patients, which were divided into two subgroups, according to the duration of mechanical ventilation (Group A < 48 hours; Group B = 48 hours). In Group A (< 48 hours) we analysed the data of the day of intubation only, whereas in Group B (= 48 hours) we analysed three more points in time (day 2, day 3 and the day of extubation). The statistical analyses were divided into a descriptive analysis of all values, a comparison of both groups on day 1 of mechanical ventilation, and a comparison of day 1, day 2, day 3 and the day of extubation in Group B. Further, we analysed the correlation of VDalv/VT, VDphys/VT, VD-Bohr/VT, slope-CO2, VCO2 and other VCAP-derived parameters. Results: There was a significant difference in CO2-derived parameters (pACO2, pECO2, VCO2, pa-etCO2 and pa-ACO2, slope-CO2), and in physiologic and alveolar dead space fractions between patients with short-term, and with long-term mechanical ventilation. Physiologic and alveolar dead space fractions and CO2-derived parameters (petCO2, pACO2, VCO2, pa-etCO2 and pa-ACO2) changed significantly over time in the group of patients with prolonged mechanical ventilation. Physiologic dead space fraction showed a correlation with the duration of mechanical ventilation. Further, there was a correlation between alveolar and physiologic dead space fractions. In addition, both dead space fractions correlated with the arterial to end-tidal CO2, and with arterial to alveolar pCO2 differences. Whereas slope-CO2 showed no significant difference in the whole group of patients with prolonged mechanical ventilation over time, in patients with RSV-infection slope CO2 was significantly lower on the day of extubation compared with the data on days 2 and 3 of mechanical ventilation. Conclusion: VCAP is a very useful monitoring tool for paediatric patients, displaying different CO2-parameters, and furthermore time based and volume based capnograms breath-by-breath. It improves our understanding about pathophysiologic changes in respiratory disorders, helps to optimize PEEP-titration in patients with ARDS and gives us useful information about severity of lung disease and the duration of mechanical ventilation.