S76 Use of parasternal intercostal electromyography to investigate the impact of comorbid heart failure on neural respiratory drive in COPD

Introduction and objectives Heart failure is a common comorbidity of COPD and contributes to increased breathlessness and adverse clinical outcomes. Neural respiratory drive (NRD) is closely related to breathlessness intensity in COPD. This study aimed to investigate the impact of comorbid left heart failure (COPD-HF) on NRD in patients with COPD. We hypothesised that NRD would be higher during an inspiratory threshold loading protocol (ITL) in COPD-HF than in COPD patients without left heart failure. Methods COPD and COPD-HF patients underwent incremental ITL at 12%, 24%, 36%, 48% and 60% of maximal inspiratory mouth pressure (PImax). NRD was recorded continuously using 2nd intercostal space transcutaneous electromyography (EMGpara). EMGpara signals were converted to root mean square (RMS), normalised to peak RMS EMGpara during maximal inspiratory manoeuvres (EMGpara%max) and multiplied by respiratory rate to calculate NRD index (NRDI). NRDI in COPD and COPD-HF were compared at each load using mixed effect model repeated measurement analysis. Results 11 COPD patients without left heart failure (mean (SD) age 69(7) years, FEV1%predicted 49.3 (16.4)%, VC%predicted 99.8 (22.0)%, PIMax 55.7 (15.8)cmH2O) and 11 COPD-HF patients (mean (SD) age 72(6) years, FEV1%predicted 54.8 (13.6)%, VC%predicted 86.8 (17.4)%), PIMax 53.1 (30.9)cmH2O) were studied. mMRC dyspnoea scores were higher in COPD-HF (median (IQR) 3 (2 – 4) than in COPD (median (IQR) 2 (1 to 3), p=0.0406). 11/11 COPD patients completed all loads of the ITL protocol to 60% PImax, compared to 4/11 patients in the COPD-HF group (p=0.0039). There were significant fixed effects of diagnosis (p=0.0136), load (p Conclusions Observations of higher levels of NRDI at equivalent inspiratory threshold loads in COPD-HF suggests that heart failure further increases the mechanical load on the respiratory muscles in COPD. Contributions of potential aetiological factors, such as reduced lung and chest wall compliance, require further study.