title: Changes in TcPCO2 regarding pulmonary mechanics due to pneumotachometer dead space in ventilated newborns.
abstract: The aim of this study was to analyze the effect of added dead space on PaCO2 after application of a pneumotachometer during the measurement of pulmonary mechanics. The study was based on 24 observations of TcPCO2 changes during the measurement of pulmonary function in 9 newborns subjected to mechanical ventilation. All newborns remained stable during the 23 minutes of the test. The introduction of a low dead space pneumotachometer (1.7 mL) for 10 minutes led to an increase in TcPCO2 of 5.40 +/- 2.66 mm Hg, from 39.76 +/- 8.69 to 45.17 +/- 9.22. Pulmonary mechanics indexes that correlated with the percentage of CO2 increase were peak inspiratory flow and expiratory time/time constant. When the pneumotachometer was removed, TcPCO2 fell but remained 0.99 +/- 2.13 mm Hg above basal TcPCO2. Final TcPCO2 tended to relate negatively with the minute volume. We conclude that this transient increase in PaCO2 should be born in mind in neonates with a high basal level and can be prevented by maintaining a long expiratory time and a high minute volume.
authors.affiliation: Neonatal Unit, Clínic Hospital, Pediatric Integrated Unit (Hospitals Clínic, Sant Joan de Déu and Casa Maternitat), University of Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Figueras
authors.forename: J M
authors.initials: JM
authors.lastname: Rodriguez-Miguélez
authors.forename: F
authors.initials: F
authors.lastname: Botet
authors.forename: M
authors.initials: M
authors.lastname: Thió
authors.forename: R
authors.initials: R
authors.lastname: Jiménez
mesh_terms: D001785:Blood Gas Monitoring, Transcutaneous; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000503:physiopathology*; D012121:Respiration, Artificial / Q000295:instrumentation / Q000379:methods; D012680:Sensitivity and Specificity