Validation of a transcutaneous CO(2) monitor in adult patients with chronic respiratory failure

Abstract

Background: Home mechanical ventilation is usually started in hospital as arterial blood gas sampling is deemed necessary to monitor CO(2) and O(2) adequately during institution of ventilatory support. A non-invasive device to reliably measure CO(2) transcutaneously would alleviate the need for high care settings for measurement and open the possibility for home registration.

Objectives: In this study we investigated whether the TOSCA® transcutaneous CO(2) (PtcCO(2)) measurements, performed continuously during the night, reliably reflect arterial CO(2) (PaCO(2)) measurements in adults with chronic respiratory failure.

Methods: Paired measurements were taken in 15 patients hospitalised to evaluate their blood gas exchange. Outcomes were compared 30 min, 2, 4, 6 and 8 h after attaching the sensor to the earlobe. A maximum difference of 1.0 kPa and 95% limits of agreement (LOA) of 1 kPa between CO(2) pressure measurements, following the analysis by Bland and Altman, were determined as acceptable.

Results: Mean PtcCO(2) was 0.4 kPa higher (LOA -0.48 to 1.27 kPa) than mean PaCO(2) after 30 min. These figures were 0.6 kPa higher (LOA -0.60 to 1.80 kPa) after 4 h, with a maximum of 0.72 kPa (LOA 0.35 to 1.79 kPa) after 8 h. The corresponding values for changes in PtcCO(2) versus PaCO(2) were not significant (ANOVA).

Conclusions: PtcCO(2) measurement, using TOSCA, is a valid method showing an acceptable agreement with PaCO(2) during 8 h of continuous measurement. Therefore, this device can be used to monitor CO(2) adequately during chronic ventilatory support.