Cardiorespiratory coupling is associated with exercise capacity in patients with chronic obstructive pulmonary disease

Table 3 Main correlations with distance and distance saturation product (DSP) as assessed by 6MWT

Variable	Distance		DSP
Variable	r value	p value	r value	P value
Age, years	− 0.53	< 0.001	− 0.53	< 0.001
Synchrogram Index	0.42	0.001	0.41	0.001
BMI, kg/m²	− 0.07	0.62	− 0.05	0.69
Male, n (%)	0.13	0.34	0.17	0.21
CAT	− 0.44	< 0.001	− 0.44	< 0.001
mMRC	− 0.53	< 0.001	− 0.61	< 0.001
Smoking, n (%)	0.02	0.86	0.03	0.83
Presence of emphysema, n (%)	− 0.42	0.002	− 0.45	0.001
EF, %	− 0.12	0.39	− 0.13	0.35
E/e' ratio	− 0.34	0.06	− 0.35	0.06
Left atrial, mm	0.04	0.78	0.09	0.50
Presence of diastolic dysfunction	0.07	0.59	0.05	0.72
EOS count, number/l	0.08	0.59	0.10	0.45
IgE, pg/ml	− 0.13	0.37	− 0.11	0.43

Presence of emphysema was defined as presence of emphysema in the high-resolution computed tomography
Significant correlation was defined as P < 0.05
6MWD six minutes walking distance, DSP distance saturation product, BMI body mass index, 6MWT six minutes walking test, HS-CRP high sensitivity C reactive protein, EF ejection fraction, LA left atrial, CAT chronic obstructive pulmonary disease assessment test, mMRC modified medical research council, E/e′ ratio the ratio of the trans-mitral early peak velocity over early diastolic mitral annulus velocity, EOS.count eosinophil count

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