Evaluation of a Novel Portable Capnograph (MARIE) in Adult Postoperative Patients

Postoperative respiratory complications are common and sometimes hard to detect early. Desaturation is a late sign of reduced minute ventilation, especially if the patient is on supplemental oxygen, and measurement of arterial or endtidal CO2 will rapidly detect a reduction in minute ventilation. Capnography offers a non-invasive and continuous measure of end-tidal expiratory pressure of carbon dioxide (EtCO2). Capnography is not a standard in postoperative care but rather quite rare. In the present study we evaluate a novel portable capnography device, MARIE, in postoperative patients.

1. The primary outcome is to describe the correlation of end-tidal CO₂ (EtCO₂) measurements between MARIETM (Oxlantics Medical) and Philips Intelli Vue X3 Microstream. 2. Secondary outcomes include

1. Correlation between PaCO₂ and EtCO₂ measured by MARIE and Philips Intelli Vue X3 Microstream, respectively. 2. Time trajectories of PaCO₂ and EtCO₂ measured using MARIE and Philips Intelli Vue X3 Microstream, respectively 3. The overall agreement between the EtCO2 measured by MARIE and Philips Intelli Vue X3 Microstream and PaCO2 4. Respiratory rate measured by MARIE compared to manual counting and Philips Intelli Vue X3. 5. Comparison of oxygen flow by MARIE and the rotameter. 6. Comfort as reported by patient. 7. Usability as reported by nurse. 8. Reasons for premature termination of MARIE 9. Registration of technical problems, for example unexpected shut downs and blockage by mucus.

MARIE will be applied immediately after tracheal extubation after surgery. CO2 values from MARIE will be compared to EtCO2 and PaCO2 derived from capnography equipment routinely used in the hospital and blood gas analysis, at set intervals in the postoperative ward. Respiratory rate will be compared to our standard care monitors, ie Philips Intelli Vue X3, alongside manual counting. Rate of oxygen delivery, when applicable, will also be compared to the rotameter.