A Novel Mainstream Capnometer System for Non-invasive Positive Pressure Ventilation

Capnometry is a method to measure carbon dioxide (CO₂) in exhaled gas and it has been used to monitor patient respiratory status. CO₂ monitoring is also used for patients receiving non-invasive positive pressure ventilation (NPPV) therapy during mechanical ventilation. Ventilators actively dilute exhaled gas during non-invasive ventilation. In order to accurately measure end-tidal CO₂, an adequate amount of expired gas needs to be filled in a CO₂ measurement cell before expiratory positive airway pressure (EPAP) gas from the ventilator arrives to the cell. This is the reason why it is difficult to measure CO₂ stably during non-invasive ventilation using the conventional CO₂ measurement method. Therefore, we developed NPPV cap-ONE mask, which accurately measures CO₂ in exhaled gas during non-invasive ventilation. In this study, we evaluated the basic performance of the NPPV cap-ONE mask system. The NPPV cap-ONE mask system could accurately measure CO₂ in exhaled gas comparing to the conventional device in this study.