Comparison of Calibration Drift in Transcutaneous Carbon Dioxide Monitoring Devices for Overnight Level 4 Sleep Study in Hong Kong Children

Abstract

Abstract Background: Level 4 sleep study with transcutaneous carbon dioxide (TcCO2) monitoring is a simple, non-invasive method to investigate sleep-related hypoventilation. However, calibration drift in the TcCO2 device weakens its reliability. Materials and Methods: We conducted a retrospective study of 61 patients from <1 to 20 years of age in our paediatric unit, who were assigned one of the two models of TcCO2 machines (SenTec Digital Monitoring System and Tina Radiometer Copenhagen TCM4 Transcutaneous Blood Gas Monitor) for performing the Level 4 sleep study, using capillary blood gas carbon dioxide (pCO2) level at the first and ninth hours as a reference. Results: For the 9-h sleep study, there was no change in the attachment site, membrane, or sensor. The TcCO2–pCO2 difference at the ninth hour in the former model was 0.03 ± 0.61 kPa (0.26 ± 4.59 mm Hg), which was favourable in comparison to the latter (–0.45 ± 1.25 kPa or –3.38 ± 9.38 mm Hg), with P = 0.014; the TcCO2–pCO2 difference between monitors A and B at the ninth hour compared to the first hour did not differ substantially from the former (P = 0.160), but a statistically significant difference was noted in the latter model (P = 0.037). Both findings indicated calibration drift and hence less accurate TcCO2 readings in the latter model. Conclusion: In overnight extended use, calibration drift might affect the diagnosis and management of sleep-related hypoventilation.