[The role and utilization of transcutaneous capnography in respiratory failure patients. Chronicles: A review of the literature and an expert opinion].

INTRODUCTION: Transcutaneous capnography (PtcCO2) provides a non-invasive estimate of partial arterial pressure of carbon dioxide in the blood and is an increasingly widely used tool for assessing alveolar hypoventilation, particularly nocturnal hypoventilation, in patients with chronic respiratory failure. That much said, its reliability in clinical practice requires satisfactory understanding of the relevant technical principles, conditions of implementation, and analysis methods.

METHODS OF ANALYSIS: This work is based on expert opinions from the Ventilatory Assistance and Oxygen Therapy Group (GAVO2) of the French-speaking Pulmonology Society (SPLF). The data available in the literature were analyzed and discussed in view of providing practical advice on the performance, analysis, and interpretation of nocturnal PtcCO2 recordings in adults.

RESULTS: Under optimal technical conditions, PtcCO2 correlates well with PaCO2, with bias generally lower than 0.5kPa. The quality of recording is a determining factor and depends on proper sensor placement, continuous recording for a sufficient amount of time, and prior analysis of the curves aimed at identifying artifacts and measurement drifts. Definitions of nocturnal hypoventilation based on PtcCO2 remain heterogeneous and are based primarily on expert opinion.

CONCLUSION: Transcutaneous capnography is a relevant non-invasive tool ensuring assessment of alveolar hypoventilation in adults with chronic respiratory failure, provided that the technical and interpretative aspects are fully mastered and rigorously applied. It should complement blood gases as part and parcel of a comprehensive clinical approach.