Quantitative assessment of walking time and postural change in patients with COPD using a new triaxial accelerometer system

Figures & data

Table 1 Baseline characteristics in COPD subjects and controls

	COPD (n = 26)	Healthy elderly subjects (n = 20)
Age, years	77 ± 6	73 ± 4
Sex, male/female	26/0**	8/12
BMI, kg/m^2	21.2 ± 3.5*	24.2 ± 2.7
GOLD stage I, II, III, IV	4/7/11/4	–
TLC, L	6.5 ± 1.0	–
DLCO, mL/min/mmHg	9.8 ± 5.2	–
PaO2, mmHg	67.8 ± 20.3	–
FVC, L	2.9 ± 0.7	2.9 ± 0.5
FEV1, L	1.3 ± 0.7**	2.2 ± 0.4
FEV1/FVC, %	43.0 ± 16.1**	77.7 ± 9.1
FEV1, %pred	52.9 ± 26.3**	124.0 ± 22.3
PImax, cmH2O	63.3 ± 23.7*	78.0 ± 24.8
PEmax, cmH2O	102.6 ± 29.4	86.8 ± 17.0
6MWD, m	381.1 ± 172.9**	536.3 ± 50.7
Borg (dyspnea)	4.3 ± 3.2*	2.6 ± 1.6
Borg (leg fatigue)	2.2 ± 2.4	1.7 ± 1.7

Notes: All data are shown as the mean ± standard deviation.

* P < 0.05;

** P < 0.01 versus controls.

Abbreviations: COPD, chronic obstructive pulmonary disease; BMI, body mass index; GOLD, Global initiative for chronic Obstructive Lung Disease; TLC, total lung capacity; DL_CO, carbon monoxide diffusing capacity; PaO₂, arterial oxygen partial pressure; FVC, forced vital capacity; FEV₁, forced expiratory volume in one second; PI_max, maximum inspiratory mouth pressure; PE_max, maximum expiratory mouth pressure; 6MWD, six-minute walking distance; Borg (dyspnea, leg fatigue), Borg scale after 6MWT.

Table 2 Comorbidities in COPD patients and healthy age-matched subjects

Comorbidities	COPD (n = 26)	Healthy elderly subjects (n = 20)
Osteoporosis	9	0
Diabetes	4	2
Chronic heart failure	3	0
Hypertension	7	7
Low back pain	6	0
Arthritis	4	3

Abbreviation: COPD, chronic obstructive pulmonary disease.

Figure 1 Activity Monitoring and Evaluation System (A-MES™). Size: 69 height × 44 width × 11.5 depth mm. Weight 28 g.

Figure 2 Measurement of a subject’s position, movement, and postural changes by the Activity Monitoring and Evaluation System (A-MES™) sensors.

Table 3 Physical activities of COPD patients and healthy elderly subjects by daily measurements

	COPD (n = 26)	Healthy elderly subjects (n = 20)	P-value
Days of measurement	4 ± 2	6 ± 1	P = 0.140
Measurement time, minutes per day	705 ± 117	764 ± 44	P = 0.097
Total time, minutes per day
Total walking	118 ± 72	210 ± 57	P < 0.001
Fast (≥2 km/hour)	36 ± 35*	82 ± 42*	P < 0.001
Slow (<2 km/hour)	69 ± 30	141 ± 40	P < 0.001
Standing	79 ± 48	80 ± 23	P = 0.920
Sitting	417 ± 116	316 ± 67	P = 0.001
Lying	107 ± 105	101 ± 65	P = 0.818
Maximum continuously active time, minutes per day
Walking	7 ± 7	10 ± 6	P = 0.027
Standing	6 ± 4	4 ± 3	P = 0.355
Sitting	65 ± 32	40 ± 11	P = 0.011
Lying	32 ± 27	41 ± 20	P = 0.250
Frequency of postural change, times per day
Total	88 ± 35	126 ± 42	P = 0.002
Getting up	37 ± 28	39 ± 25	P = 0.816
Standing up	49 ± 22	84 ± 24	P < 0.001

Notes: All data are shown as the mean ± standard deviation;

* P < 0.05 compared with slow walking time in each group.

Abbreviation: COPD, chronic obstructive pulmonary disease.

Table 4 Single correlation coefficients between physical activity and other physiologic measurements

	Total walking	Fast walking (≥2 km/hour)	Slow walking (<2 km/hour)	Standing	Sitting	Lying
Age	−0.47*	−0.65*	−0.27	−0.09	0.15	0.13
BMI	0.25	0.28	0.17	0.18	−0.26	0.27
FVC	0.26	0.41*	0.07	−0.21	−0.26	0.17
FEV1	0.40	0.42*	0.28	−0.24	−0.29	0.07
FEV1/FVC	0.38	0.29	0.37	−0.23	−0.19	0.02
%FEV1	0.33	0.34	0.26	−0.23	−0.24	0.07
PImax	0.47*	0.45*	0.39	0.14	−0.29	−0.10
PEmax	0.40*	0.42*	0.31	0.11	−0.30	−0.02
6MWD	0.52**	0.51*	0.44*	−0.09	−0.34	0.05
Borg (dyspnea)	−0.41*	−0.36	−0.32	−0.05	0.08	0.24
Borg (leg fatigue)	−0.08	0.07	−0.04	−0.11	0.06	0.11
QF	0.46*	0.60*	0.33	0.26	−0.24	−0.17
MRC dyspnea scale	−0.61**	−0.66*	−0.54*	−0.12	0.18	0.43*
CRQ (total)	0.28	0.29	0.20	0.23	0.06	−0.51**
Dyspnea	0.31	0.25	0.30	0.11	0.18	−0.40**
Fatigue	0.18	0.19	0.14	0.04	0.05	−0.29
Emotional function	0.07	0.17	0.02	0.27	−0.08	−0.12
Mastery	0.26	0.29	0.19	0.26	−0.03	−0.44*

Notes:

* P < 0.05;

** P < 0.01.

Abbreviations: BMI, body mass index; QF, quadriceps femoris muscle force; MRC, Medical Research Council; CRQ, chronic respiratory disease questionnaire; FVC, forced vital capacity; FEV₁, forced expiratory volume in one second; PI_max, maximum inspiratory mouth pressure; PE_max, maximum expiratory mouth pressure; 6MWD, six-minute walking distance; Borg (dyspnea, leg fatigue), Borg scale after 6MWT.

Table 5 Assessment of independent contributors to total walking time in patients with COPD

	B	β	P-value	95% CI
	594.19		P < 0.001	311.38–877.01
Age	−7.18	−0.58	P = 0.001	−10.75 to −3.61
6MWD	0.23	0.56	P = 0.001	0.11–0.35

Notes: R² = 0.71, analysis of variance, P < 0.001; B, partial regression coefficient; β, standardized partial regression coefficient.

Abbreviations: 6MWD, six-minute walking distance; CI, confidence interval; COPD, chronic obstructive pulmonary disease.

Table S1 Single correlation coefficients between total time and maximum continuously active time measured by A-MES™ and video recording in ten healthy elderly subjects (Pearson’s product–moment correlation coefficient)

	Total time	Maximum continuously active time
Walking	0.986**	0.995**
Standing	0.940**	0.949**
Sitting	0.987**	0.982**
Lying	0.992**	0.994**

Notes:

** P < 0.01. Pearson’s product-moment correlation coefficient = r.

Abbreviation: A-MES, Activity Monitoring and Evaluation System.

Table S2 Intraclass reliability coefficients for days 2–7 of A-MES™ activity monitoring in a group of 10 COPD patients and 12 healthy elderly subjects

	Day 2	Day 3	Day 4	Day 5	Day 6	Day 7
Walking time	0.943**	0.961**	0.974**	0.981**	0.982**	0.985**
Standing time	0.754**	0.915**	0.941**	0.964**	0.968**	0.969**
Sitting time	0.865**	0.919**	0.934**	0.951**	0.957**	0.962**
Lying time	0.778*	0.824**	0.862**	0.897**	0.913**	0.918**

Notes:

* P < 0.05;

** P < 0.01.

Abbreviations: A-MES, Activity Monitoring and Evaluation System; COPD, chronic obstructive pulmonary disease.