This study aimed to elucidate the influential parameter, acquired from the analyses of nasal capnography waveforms, for the elevated plasma brain natriuretic peptide (BNP) levels in patients (n = 34) with heart failure (HF). The capnography waveforms were analyzed to evaluate changes in end-tidal CO2 (ETCO2) values and expiratory and inspiratory durations. The relationship between these parameters, estimated from capnography analyses and plasma BNP, was then evaluated. Mean ETCO2 values and BNP levels showed a strong negative correlation (R2 = 0.6355, p < 0.0001) in HF patients with chronic kidney disease (CKD) (R2 = 0.6355, p < 0.0001). The ETCO2 value was the most influential parameter that indicated elevated BNP levels in HF patients with CKD (β = - 0.577; p = 0.031). The mean ETCO2 level could be a potentially influential parameter reflecting elevated BNP levels in HF patients, especially in HF patients with CKD. Respiratory parameters, acquired from detailed nasal capnography analyses, might be reasonable for evaluating the severity of HF. Graphical abstract.
Keywords: Capnography; ETCO2; Heart failure; Unstable respiration.