Table 3 Determinants of the absolute bias levels.

From: Preclinical evaluation of noncontact vital signs monitoring using real-time IR-UWB radar and factors affecting its accuracy

Models

Variables

Univariate

Multivariate model 1

Multivariate model 2a

Estimate (95% CI)

p-value

Estimate (95% CI)

p-value

Estimate (95% CI)

p-value

Absolute bias of RR

Posture supine vs. sitting

0.104 (0.039 to 0.168)

0.002

0.186 (0.122 to 0.251)

 < 0.001

0.103 (0.039 to 0.168)

0.002

age < 50 vs. ≥ 50 years

0.115 (− 0.241 to 0.472)

0.529

0.130 (− 0.261 to 0.521)

0.515

0.189 (− 0.211 to 0.589)

0.371

Sex M vs. F

0.056 (− 0.266 to 0.377)

0.736

− 0.071 (− 0.399 to 0.257)

0.671

0.036 (− 0.300 to 0.371)

0.839

BMI (kg/m2)

− 0.015 (− 0.055 to 0.025)

0.468

− 0.004 (− 0.047 to 0.038)

0.837

− 0.024 (− 0.067 to 0.019)

0.290

RR < 18 breath/min

0.809 (0.700 to 0.918)

 < 0.001

0.864 (0.753 to 0.974)

 < 0.001

–

–

Absolute bias of HR

Posture supine vs. sitting

0.158 (− 0.073 to 0.389)

0.181

0.308 (0.063 to 0.553)

0.014

0.157 (− 0.073 to 0.389)

0.181

age < 50 vs. ≥ 50 years

3.201 (0.983 to 5.419)

0.007

0.051 (− 0.031 to 0.132)

0.229

0.056 (− 0.027 to 0.134)

0.180

Sex M vs. F

1.800 (− 0.291 to 3.891)

0.098

1.429 (− 0.702 to 3.559)

0.195

1.588 (− 0.459 to 3.635)

0.144

BMI (kg/m2)

0.225 (− 0.036 to 0.485)

0.098

0.102 (− 0.196 to 0.400)

0.506

0.095 (− 0.192 to 0.382)

0.528

HR < 70 bpm

0.932 (0.493 to 1.371)

 < 0.001

1.074 (0.616 to 1.532)

 < 0.001

–

–

 ≥ 80 bpm

0.316 (− 0.282 to 0.914)

0.301

0.223 (− 0.385 to 0.831)

0.472

–

–

  1. Linear mixed effect models were performed with individuals as the random term were used to estimate the effects of the factors.
  2. BMI body mass index, M male, F female, HR heart rate, RR respiratory rate.
  3. aMultivariate model 2 = multivariate model 1 minus RR (or HR).
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