Monitoring: Equipment and Computers
Background and Goal of Study: Arterial blood gas analysis (ABGA) remains the gold-standard to determine carbon dioxide partial pressure (paCO2). End-tidal techniques (petCO2) are easy to establish, but may be inaccurate. A new transcutaneous monitor (ptcCO2) allows continuous measurement of CO2. Accuracy and precision are evaluated in an animal model.
Materials and Methods: After approval of the local ethics committee for animal research petCO2 (Datex Ohmeda, Helsinki/Finland), paCO2 (ABL500, Radiometer/Denmark), and ptcCO2 (TCM4, Radiometer/Denmark) were determined simultaneously in six intubated and ventilated house pigs during normo-, hyper-, and hypoventilation. The bias for the measurement was calculated as Bet = paCO2 − petCO2, and Btc = paCO2 − ptcCO2. T-test was used for statistical analysis, p < 0.05 was considered significant.
Results and Discussions: 61 data sets (petCO2, paCO2, and ptcCO2) were acquired in six female house pigs (30 ± 3 kg). During normoventilation (respiratory rate 13min−1, tidal volume 10 ml kg−1, paCO2 = 40.0 ± 4.0mmHg, n = 27) bias for the end-tidal (Bet = +3.0 ± 2.3 [−0.2 to +10.0] mmHg) and transcutaneous measurement (Btc = −4.5 ± 6.0 [−16.1 to 3.1]) of paCO2 were comparable. During hypoventilation (respiratory rate 6 min−1, tidal volume 6 ml kg−1, paCO2 = 55.8 ± 5.7 mmHg, Bet = −1.7 ± 6.8 mmHg, Btc = −3.8 ± 4.9 mmHg, n = 17) and hyperventilation (respiratory rate 21 min−1, tidal volume 12mlkg−1, paCO2 = 28.7 ± 4.3mmHg, Bet = +2.6 ± 0.9mmHg, Btc = −4.1 ± 4.8 mmHg, n = 17) no difference in bias could be found.
Conclusion(s): In this trial in an animal model a good correlation between the three different techniques to determine paCO2 was found during normoventilation as well as during hypo- and hyperventilation. Transcutaneous and end-tidal monitoring allow reliable and comparable readings of paCO2.