Capnography has been studied for decades as a potential diagnostic tool for suspected pulmonary embolism. Despite technological refinements and its combination with other non-invasive instruments, no evidence to date allows recommending the use of expired carbon dioxide measurement as a rule-out test for pulmonary embolism without additional radiological testing. Further investigations are, however, still warranted.
Verschuren, F., & Perrier, A. (2010). Splendors and miseries of expired CO2 measurement in the suspicion of pulmonary embolism. Critical Care, 14(1), 110. https://doi.org/10.1186/cc8838 (Original work published 2010)