Exercise Limitation in Children and Adolescents with Mild-to-Moderate Asthma

Figures & data

Table 1 Characteristics of the Study Groups

	Asthma Group (n=45)	Control Group (n=61)	P-value
Male gender, n (%)	32 (71.1)	49 (80.3)	0.269
Age, years	12.2 ± 2.1	12.5 ± 2.3	0.481
Height, cm	154.9 ± 13.8	157.5 ± 15.1	0.360
Weight, kg	52.0 ± 15.5	50.1 ± 13.7	0.505
BMI, kg/m^2	21.4 ± 4.5	19.9 ± 3.4	0.056
BMI, z-score	0.80 ± 0.91	0.32 ± 1.09	0.019
ACT, median (range)	23 (21–25)	NA
Physical activity questionnaire
Inactive, n (%)	28 (62.2)	18 (29.5)	0.002
Spirometry
FEV1, L	2.4 ± 0.6	2.9 ± 0.9	<0.001
FEV1, %	91.3 ± 9.4	100.9 ± 10.5	<0.001
FEV1 z-score	−0.74 ± 0.81	0.08 ± 0.89	<0.001
FVC, L	2.9 ± 0.7	3.3 ± 1.1	0.019
FVC, %	90.4 ± 14.1	96.4 ± 12.2	0.021
FVC, z-score	−0.83 ± 1.21	−0.32 ± 1.04	0.022
FEV1/FVC	0.87 ± 0.05	0.91 ± 0.04	<0.001
FEV1/FVC z-score	0.01 ± 0.81	0.81 ± 0.83	<0.001
FEF25–75, L/sec	2.1 ± 1.1	2.8 ± 1.3	0.004
FEF25–75, %	80.3 ± 14.9	99.4 ± 19.6	<0.001
FEF25–75, z-score	−0.94 ± 0.73	−0.04 ± 0.93	<0.001

Note: Values are mean ± SD unless stated otherwise.

Abbreviations: BMI, body mass index; ACT, asthma control test; FEV₁, forced expiratory volume at 1 s; FVC, forced vital capacity; FEF_25–75, forced expiratory flow at 25–75% of FVC.

Table 2 CPET Parameters

	Asthma Group (n=45)	Control Group (n=61)	P-value
Maximal work, watts	136.3 ± 29.2	151.9 ± 39.0	0.021
Test time, min	10.1 ± 1.4	10.6 ± 1.7	0.075
O2peak, mL/kg/min	36.1 ± 7.4	41.3 ± 6.7	<0.001
O2peak, % predicted	85.2 ± 19	93.8 ± 16.5	0.015
O2 at AT, mL/kg/min	25.1 ± 6.6	29.0 ± 6.0	0.002
AT % O2peak, %	69.1 ± 9.5	70.6 ± 10.4	0.448
HRmax, bpm	188 ± 9	188 ± 10	0.917
O2peak/HR, mL/beat	9.6 ± 2.3	10.9 ± 3.1	0.020
O2peak/work, mL/watts×min	13.2 ± 1.2	13.4 ± 1.5	0.478
RER	1.12 (1.1–1.4)	1.16 (1.1–1.4)	0.066
E, L/min	65.1 ± 14.7	72.8 ± 19.4	0.023
E/MVV	0.79 ± 0.12	0.73 ± 0.14	0.045
E/30×FEV1	0.77 ± 0.12	0.71 ± 0.13	0.041
E/O2	36.4 ± 4.4	36.1 ± 4.7	0.767
E/CO2	31.2 ± 3.3	31.6 ± 3.4	0.526
Ventilation efficiency slope	29.6 ± 3.4	30.2 ± 3.5	0.437
SpO2 decrease	2 (1–3)	2 (1–3)	0.876
Minimum SpO2	95 (94–98)	96 (94–98)	0.304
Borg dyspnea	7 (5–8)	7 (6–8)	0.422

Notes: Values are mean ± SD or median (range) and were compared with t test or Mann–Whitney U, respectively.

Abbreviations: CPET, cardiopulmonary exercise testing; AT, anaerobic threshold; HR, heart rate; RER, respiratory exchange ratio; MVV, maximal voluntary ventilation.

Figure 1 Numbers (in boxes) and percentages (x-axis) of children with low O₂peak, EIB, VL and physical deconditioning in the two study groups. The number of inactive participants is also presented. Comparisons were performed with chi-square or Fisher’s exact test. *Two children had both EIB and VL.

Abbreviations: EIB, exercise-induced bronchoconstriction; VL, ventilatory limitation.

Table 3 Determinants of Cardiopulmonary Exercise Performance*

Factor	Unadjusted Effect		Adjusted Effect R^2 0.455
	Beta	P	Beta	P
Male gender	0.089 (–0.11 to 0.28)	0.367	0.044 (–0.20 to 0.11)	0.567
Age	0.143 (–0.05 to 0.34)	0.143	0.005 (–0.15 to 0.16)	0.949
BMI, z-score	–0.247 (–0.44 to –0.06)	0.011	–0.113 (–0.28 to 0.05)	0.173
Asthma	–0.236 (–0.42 to –0.05)	0.015	–0.007 (–0.16 to 0.17)	0.932
EIB	–0.025 (–0.22 to 0.17)	0.801	–0.057 (–0.22 to 0.11)	0.497
Ventilatory limitation	–0.018 (–0.21 to 0.17)	0.853	–0.108 (–0.28 to 0.06)	0.213
Physical deconditioning	–0.645 (–0.79 to 0.50)	<0.001	–0.653 (–0.82 to 0.49)	<0.001

Notes: Values are standardized linear regression coefficients beta with 95% confidence intervals in parenthesis. The unadjusted effect (univariable models) refers to the effect of each factor separately. The adjusted effect (multivariable model) refers to the combined effect of these factors when adjusted for each other. The achieved power of the multivariable model was 99.99%. *O₂peak % predicted.

Abbreviations: BMI, body mass index; EIB, exercise-induced bronchoconstriction.