Diagnosis and severity assessment of COPD using a novel fast-response capnometer and interpretable machine learning by Talker, L, Dogan, C, Neville, D, Lim, RH, Broomfield, H, Lambert, G, Selim, A, Brown, T, Wiffen, L, Carter, J, Ashdown, HF, Hayward, G, Vijaykumar, E, Weiss, ST, Chauhan, A, Patel, AX