13 March 2017
To evaluate the heart rate variability (HRV) indices and heart rate (HR) responses during isometric contraction (IC) and Valsalva maneuver (VM) in COPD patients.
Twenty-two stable moderate to severe COPD patients were evaluated. R-R intervals were recorded (monitor Polar ® S810i) during dominant upper limb IC (2 minutes). Stable signals were analyzed by Kubios HRV ® software. Indices of HRV were computed in the time domain (mean HR; square root of the mean squared differences of successive RR intervals [RMSSD] and HRV triangular index [RR tri index]) and in the frequency domain (high frequency [HF]; low frequency [LF] and LF/HF ratio). The HR responses were evaluated at rest, at the peak and at the nadir of the VM (15 seconds). The Valsalva index was also calculated.
During IC: time domain indices (mean HR increased [ P=0.001], RMSSD, and RR tri index decreased [ P=0.005 and P=0.005, respectively]); frequency domain indices (LF increased [ P=0.033] and HF decreased [ P=0.002]); associations were found between forced expiratory volume in 1 second (FEV 1) vs RMSSD ( P=0.04; r=−0.55), FEV 1 vs HR ( P=0.04; r=−0.48), forced vital capacity (FVC) vs RMSSD ( P=0.05; r=−0.62), maximum inspiratory pressure (MIP) vs HF ( P=0.02; r=0.68). FEV 1 and FVC justified 30% of mean HR. During VM: HR increased ( P=0.01); the nadir showed normal bradycardic response; the Valsalva index was =0.7.