COPD assessment test and FEV₁: do they predict oxygen uptake in COPD?

Figures & data

Figure 1 Study flowchart.

Abbreviations: COPD, chronic obstructive pulmonary disease; GOLD, Global Initiative for Chronic Obstructive Lung Disease.

Table 1 COPD patients’ anthropometric and clinical characteristics

Characteristics	COPD (n=27)
Age, years	65.0±7.3
Gender, male/female	21/5
BMI, kg/m^2	26.6±5.0
CATs	12.4±7.4
Lung function
FEV1/FVC	49.1±15.7
FEV1, % predicted	56.4±19.4
GOLD stage, n (% of patients)
1. Mild	3 (11.1)
2. Moderate	13 (48.1)
3. Severe	7 (25.9)
4. Very severe	4 (14.9)
GOLD risk class, n (% of patients)
A	7 (25.9)
B	10 (37.1)
C	2 (7.4)
D	8 (29.6)

Note: Data are presented as mean ± SD or number (%).

Abbreviations: BMI, body mass index; CATs, COPD assessment test score; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease.

Table 2 Variables obtained in the CPET in COPD patients

CPET variables	COPD (n=27)
Rest
HR peak, bpm	77.1±9.8
SBP, mmHg	137.0±14.0
DBP, mmHg	82.4±8.9
SpO2, %	94.0±2.4
BORG dyspnea score	0.2±0.8
BORG lower limbs fatigue score	0.1±0.6
Incremental exercise
VO2peak, mL⋅min^−1	972.6±298.9
VO2peak, mL⋅min^−1⋅kg^−1	12.8±3.0
VO2peak, % predicted	62.1±14.9
VCO2peak, mL⋅min^−1	1,080±389.5
RER	1.1±0.1
VE, L⋅min^−1	43.4±17.0
VE/MVV	73.9±22.8
HR peak, bpm	124.7±15.9
SBP peak, mmHg	204.4±24.5
DBP peak, mmHg	106.6±10.3
SpO2 peak, %	86.8±8.9
Power, W	72.8±39.2
Exercise time, seconds	568.4±142.0
BORG dyspnea score peak	6.1±2.3
BORG lower limbs fatigue score peak	4.3±3.6

Note: Values are presented as mean ± SD.

Abbreviations: CPET, cardiopulmonary exercise test; DBP, diastolic blood pressure; HR, heart rate; MVV, maximal voluntary ventilation; RER, respiratory exchange ratio; SBP, systolic blood pressure; SpO₂, oxygen saturation; VCO₂, carbon dioxide output; VE, minute ventilation; VO₂, pulmonary oxygen uptake.

Figure 2 Significant correlations between (A) CATs and VO₂peak and (B) FEV₁ (% pred.) and VO₂peak in COPD patients.

Abbreviations: CATs, COPD Assessment Test score; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; % pred., percentage of predicted value; VO₂, pulmonary oxygen uptake.

Table 3 VO₂peak estimation model based on CATs in COPD patients

Variable	Coefficient	Standard error	P-value
R^2=0.200
Constant	15.148	1.072	<0.001
CATs	−0.185	0.0742	0.019

Abbreviations: CATs, COPD assessment test score; COPD, chronic obstructive pulmonary disease; VO₂, pulmonary oxygen uptake.

Table 4 VO₂peak estimation model based on FEV₁ (% pred.) in COPD patients

Variable	Coefficient	Standard error	P-value
R^2=0.501
Constant	6.490	1.338	<0.001
FEV1 (% pred.)	0.113	0.0224	<0.001

Abbreviations: COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; % pred., percentage of predicted value; VO₂, pulmonary oxygen uptake.

Table 5 VO₂peak estimation model based on CATs and FEV₁ (% pred.) in COPD patients

Variable	Coefficient	Standard error	P-value
R^2=0.553
Constant	8.441	1.774	<0.001
CAT	−0.0999	0.0599	0.109
FEV1 (% pred.)	0.1000	0.0230	<0.001

Abbreviations: CATs, COPD assessment test score; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; % pred., percentage of predicted value; VO₂, pulmonary oxygen uptake.