Evaluation of a System for Transcutaneous Long-Term Capnometry

Abstract

Background: The measurement of CO₂ partial pressure (PCO₂) is of great importance. Former systems of transcutaneous capnometry combining the measurement of oxygen partial pressure (PO₂) and PCO₂ had their limitations due to skin irritations caused by the heating-up of the sensor and a short application time of 4 h. Objectives: To evaluate for the first time combined monitoring of transcutaneous PCO₂ (tcPCO₂) and oxygen saturation applying a lower temperature (sensor temperature 42°C) and a new sensor technology in healthy individuals during sleep. Methods: Twenty-nine healthy individuals [12 males, age 35.2 ± 17.0 years, body height: 170.2 ± 12.0 cm (mean ± SD), weight: 76.3 ± 15.8 kg, body mass index 26.5 ± 5.4] were monitored for more than 6 h at night with the TOSCA 500 instrument (Radiometer, Basel, Switzerland). tcPCO₂ was continuously monitored and its correlation with selective measured capillary PCO₂ values (PcapCO₂) was monitored at 0.00 and 4.00 h. Results: At 0.00 h, PcapCO₂ was 37.1 ± 5.1 mm Hg and tcPCO₂ was 43.4 ± 6.6 mm Hg (p < 0.001). At 4.00 h, PcapCO₂ was 37.0 ± 5.6 mm Hg and tcPCO₂ was 43.5 ± 5.4 mm Hg (p < 0.001). PcapCO₂ and tcPCO₂ were positively and significantly correlated (0.00 h: r = 0.5, p < 0.02 and 4.00 h: r = 0.72 and p < 0.001) at both time points. In the course of the night, there was no significant drift in the tcPCO₂ values. Conclusion: The investigated system enables stable measurement of tcPCO₂ without relevant drift in healthy individuals and does not require recalibration. tcPCO₂ is highly suitable as a measure of PcapCO₂ because the two parameters are highly correlated and there is no inconvenience to the patient.