Upper-extremity function prospectively predicts adverse discharge and all-cause COPD readmissions: a pilot study

Figures & data

Figure 1 Summary of the procedures used in this study.

Abbreviations: CAT, COPD Assessment Test; CCI, Charlson Comorbidity Index; COPDRE, COPD-related exacerbations; UEF, upper-extremity function.

Figure 2 (A) UEF experimental set-up, (B) sensor outputs, and (C) UEF frailty score.

Notes: (A) Wearable motion sensors were used to capture forearm and upper-arm motion, and ultimately the elbow angular velocity during rapid elbow flexion/extension. Written consent was obtained from the participant to publish this figure. (B) Relative elbow angular velocity was obtained by subtracting sensor outputs. Results for one non-frail, one pre-frail, and one frail are presented. (C) The signals from section (B) were fed into our mathematical model to compute four criteria: slowness, exhaustion, weakness, and flexibility. The UEF frailty score was ultimately calculated based on these components.
Abbreviation: UEF, upper-extremity function.

Table 1 Definitions of UEF parameters

UEF parameter	Definition	Criterion
Speed	Mean value of elbow angular velocity range (maximum minus minimum speed)	Slowness
Range of motion	Mean value of elbow flexion range	Flexibility
Moment	Mean value of maximum moments on elbow within each flexion/extension estimated from moment of inertia of forearm and hand, and elbow motion	Weakness
Speed reduction	Difference in angular velocity range between the last and the first 5 seconds of elbow flexion as a percentage of the initial angular velocity range	Exhaustion
Speed variability	Coefficient of variation of angular velocity range for 20 seconds	Exhaustion
Flexion number	Number of flexion/extensions for 20 seconds	Slowness

Abbreviation: UEF, upper-extremity function.

Table 2 Sociodemographic information and health outcome measures

Variable	Non-frail group	Pre-frail group	Frail group	P-value	Effect size
Number, n (% of total)	6 (14)	14 (33)	22 (53)	–	–
Frailty score, mean (SD)	0.18 (0.091)	0.45 (0.087)	0.78 (0.11)	<0.0001*	2.21
Male, n (% of the group)	3 (50)	8 (54)	17 (78)	0.29	–
Age (years), mean (SD)	67 (11)	71 (7)	71 (8)	0.51	0.17
Stature (cm), mean (SD)	171.82 (12.80)	169.42 (9.68)	174.80 (10.03)	0.32	0.24
Weight (kg), mean (SD)	75.01 (20.56)	78.48 (19.91)	75.59 (22.03)	0.91	0.07
BMI (kg/m^2), mean (SD)	25.18 (5.74)	27.26 (5.94)	24.46 (5.96)	0.39	0.21
CAT (0–40 scale), mean (SD)	24.17 (7.02)	22.71 (9.82)	23.82 (8.85)	0.75	0.06
CCI (0–39 scale), mean (SD)	3.67 (1.37)	3.14 (1.46)	3.14 (1.67)	0.70	0.12
Unfavorable discharge disposition, n (% of the group)	0 (0)	2 (15)	12 (55)	0.0038*	–
Hospital length of stay (days), mean (SD)	6.67 (4.92)	5.77 (3.32)	7.09 (3.90)	0.56	0.15
30-day exacerbation requiring treatment, n (% of the group)	2 (33)	4 (31)	8 (40)	0.77	–
30-day readmission, n (% of the group)	0 (0)	0 (0)	4 (20)	0.047*	–

Note:

* Significant difference (P≤0.05).

Abbreviations: BMI, body mass index; CAT, COPD Assessment Test; CCI, Charlson Comorbidity Index.

Figure 3 Potential of the frailty score and its components to risk-stratify COPD patients in terms of (A) unfavorable discharge disposition and (B) 30-day readmission.

Notes: All models were adjusted for age, BMI, and sex. *Significant difference (P≤0.05).

Abbreviations: BMI, body mass index; UEF, upper-extremity function.

Figure 4 ROC curves of the logistic models predicting (A) unfavorable discharge disposition and (B) 30-day readmission.

Note: All models were adjusted for age, BMI, and sex.
Abbreviations: BMI, body mass index; ROC, receiver operating characteristic.

Table 3 Association between the frailty score and adverse health outcomes

Independent variables	Dependent variable	χ^2 or F-ratio	P-value
Frailty score (0–1)	Unfavorable	8.08	0.0045*
Age (years)	discharge	2.93	0.087
Sex (male)	disposition	0.0257	0.87
BMI (kg/m^2)		0.0045	0.95
Frailty score (0–1)	30-day	0.713	0.40
Age (years)	exacerbation with	1.12	0.29
Sex (male)	treatment	0.0583	0.81
BMI (kg/m^2)		7.37e-6	0.99
Frailty score (0–1)	Hospital length of	0.61	0.44
Age (years)	stay	0.00	1.00
Sex (male)		1.46	0.23
BMI (kg/m^2)		0.54	0.47
Frailty score (0–1)	30-day readmission	6.47	0.011*
Age (years)		1.71	0.19
Sex (male)		0.0508	0.82
BMI (kg/m^2)		1.22	0.27

Note:

* Significant difference (P≤0.05).

Abbreviation: BMI, body mass index.