Neural respiratory drive (NRD) measured by parasternal electromyography predicts clinical deterioration and early readmission in patients with acute exacerbation of COPD (AECOPD)

Abstract

Background Second intercostal space parasternal muscle electromyography (EMG_para) can be used as a physiological biomarker of NRD in patients with severe AECOPD (Murphy et al, Thorax 2011). We hypothesised that NRD would predict patient- and physician-defined deterioration, and early readmission in these patients.

Methods Spirometry, inspiratory capacity (IC), EMG_para, medical early warning score (MEWS) and Borg dyspnoea scale were recorded daily in patients with AECOPD admitted to a UK hospital.. Physician-defined deterioration and early readmissions were noted.

Results 120 patients were enrolled (age 70±9years, BMI 25·3±7·2kg/m² and FEV₁ 31±11% predicted). Admission-to-discharge changes (Δ) in the normalised value of EMG_para (EMG_para%max) were inversely correlated with ΔFEV₁ (r=-0·38, p<0·001) and ΔIC (r=-0·44, p<0·001). ΔEMG_para%max and ΔMEWS between consecutive recordings predicted worsening of dyspnoea, defined as ≥1point rise in Borg scale. Only ΔEMG_para%max predicted physician-defined deterioration.

Age (OR 1·08, p=0·004) and 12-month admission frequency (OR 1·29, p=0·04) predicted 28-day readmission. ΔEMG_para%max (OR 1·09, p=0·02) predicted 28-day readmission in patients under 85 years. ΔEMG_para%max (OR 1·13, p=0·007) and changes in oxygen saturation (OR 1·21, p=0·02) predicted 14-day readmission.

Conclusion NRD was a biomarker of changes in the physiological load on the respiratory system during AECOPD; it detected clinical deterioration in hospital suggesting a role as a monitoring tool. NRD also predicted early readmission, so it could be used to optimise discharge planning in COPD patients.