Table 3.

Correlations between change in neural respiratory drive and change in heart rate variability indices

Variable	ΔRMS sEMGpara tidal (μV)		ΔRMS sEMGpara max (μV)		ΔsEMGpara%max (%)
	r	P-value	r	P-value	r	P-value
ΔIE difference	−0.155	0.357	−0.034	0.468	−0.461	0.125
ΔE/I ratio	−0.229	0.292	0.119	0.389	−0.213	0.306
ΔMeanRR (msec)a)	0.357	0.193	0.595	0.060	0.643	0.043
ΔMeanHR (beats/min)	−0.574	0.068	−0.835	0.005	−0.616	0.052
ΔSDNN (msec)	0.126	0.383	−0.083	0.422	0.132	0.377
ΔRMSSD (msec)	0.253	0.272	−0.116	0.393	0.293	0.241
ΔTotal power (msec2)	−0.844	0.004	−0.614	0.053	−0.560	0.074
ΔLFnu	−0.535	0.086	−0.464	0.124	−0.269	0.260
ΔHFnu	0.535	0.086	0.464	0.124	0.269	0.260
ΔLF/HFa)	−0.143	0.368	−0.524	0.091	−0.071	0.433

sEMGpara, surface parasternal electromyogram; RMS, root mean square; ΔsEMGpara tidal, delta change of peak root mean square of sEMGpara recorded during resting; ΔsEMGpara max, delta change of peak root mean square of sEMGpara recorded during maximal inspiratory maneuver; ΔsEMGpara% max, delta change of resting parasternal EMG activity normalized to the maximal EMG evoked during maximal inspiratory maneuver; ΔIE difference, delta change of inspiratory-expiratory differences; ΔE/I ratio, delta change of expiratory/inspiratory ratio; ΔMeanRR, delta change of mean of R to R intervals for normal beats; ΔMeanHR, delta change of mean of heart rate; ΔSDNN, delta change of standard deviation of all R to R intervals; ΔRMSSD, delta change of square root of the mean of the sum of the squares of differences between adjacent R to R intervals; ΔLFnu, delta change of low frequency power in normalized units; ΔHFnu, delta change of high frequency power in normalized units; ΔLF/HF, delta change of the ratio between low and high frequency power.

Data analyzed by Pearson correlation or

^a)Spearman rank correlation.