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Table 4 Univariate Cox proportional hazards analysis of relationships between variables and exacerbation in ex-/non-smokers (n = 39)

From: Ambulatory pulse oximetry monitoring in Japanese COPD outpatients not receiving oxygen therapy

Variable

Risk ratio

95% CI

p

Age (years)

1.04

0.97 – 1.10

0.26

Unadjusted Charlson Comorbidity Index

0.93

0.57 – 1.51

0.76

Age-adjusted Charlson Comorbidity Index

1.06

0.76 – 1.46

0.74

Pack/years

1.00

0.98 – 1.01

0.69

Body mass index

0.87

0.73 – 1.03

0.10

mMRC dyspnoea grade

1.19

0.73 – 1.96

0.49

CAT score

1.08

1.00 – 1.16

0.054

PaO2

0.97

0.92 – 1.03

0.35

PaCO2

0.95

0.84 – 1.08

0.45

FEV1

0.60

0.23 – 1.53

0.28

%FEV1

0.99

0.96 – 1.02

0.45

Daytime

   

     Proportion of SpO2 values < 90% (%)

1.01

0.92 – 1.11

0.78

     Mean heart rate

1.02

0.97 – 1.07

0.42

Nighttime

   

     Proportion of SpO2 values < 90%

0.98

0.92 – 1.03

0.41

     3%ODI

0.92

0.82 – 1.02

0.12

     Mean heart rate

1.01

0.95 – 1.07

0.71

  1. CAT, Chronic obstructive pulmonary disease assessment test; CI, Confidence interval; FEV1, Forced expiratory volume in one second; mMRC, Modified Medical Research Council; ODI, Oxygen desaturation index; PaCO2, Partial pressure of arterial carbon dioxide; PaO2, Partial pressure of arterial oxygen; SpO2, Oxygen saturation by pulse oximetry.