Exercise response to oxygen supplementation is not associated with survival in hypoxemic patients with obstructive lung disease

Figures & data

Figure 1 Cohort assembly flowchart.

Abbreviations: 6MWT, 6-minute walking test; RA, room air.

Table 1 Characteristics of the study population

	Study population N=174
Age, years	70 (60, 76)
Males, n (%)	87 (50%)
BMI, kg.m^−2	23.9 (21.3, 27.9)
FEV1% pred	29.9 (23.4, 42.8)
FVC% pred	76.7 (63.2, 93.6)
FEV1/FVC%	31.3 (25.0, 43.8)
KCO% pred	47.2 (36.2, 78.3)
TLCO% pred	34.2 (25.1, 45.5)
SpO2% (resting on RA)	93 (91, 94)
Hb, g/dL	14.2±1.8

Note: Data presented as mean±SD or median (25th, 75th percentile) or number (%).

Abbreviations: BMI, body mass index; FEV₁% pred, forced expiratory volume in 1 s as a percentage of predicted; FVC% pred, forced vital capacity as a percentage of predicted; K_CO% pred, transfer coefficient of the lung for carbon monoxide as a percentage of predicted; TL_CO% pred, diffusing capacity of the lung for carbon monoxide as a percentage of predicted; S_pO₂%, oxygen saturation measured by pulse oximetry; RA, room air; Hb, blood hemoglobin level.

Table 2 6MWT performance pre- and post-oxygen

	Mean	SD	Student’s t-test	P-value
Δ6MWD, m	27.9	34.7	10.6	<0.0005
ΔBorg	1.4	1.4	13.1	<0.0005
ΔSpO2 recovery time, s	54.7	70.8	10.2	<0.0005
ΔHR recovery time, s	53.2	106.9	6.5	<0.0005
ΔBorg recovery time, s	39.5	100.3	5.1	<0.0005

Abbreviations: 6MWD, 6-minute walking distance; S_pO₂, oxygen saturation measured by pulse oximetry; HR, heart rate.

Table 3 6MWT (on oxygen) performance in both response groups

	Responders (n=77)	Nonresponders (n=97)	P-value
FiO2, %	38.1±0.1	37.1±0.1	0.341
6MWD, m	273.4±89.9	292.5±100.7	0.195
Δ6MWD, m	56.7±30.9	4.8±14.1	<0.0005
Start SpO2, %	95.4±2.4	95.5±1.8	0.740
End SpO2, %	90.7±4.0	89.8±4.7	0.217
End HR	117.6±18.6	111.8±18.8	0.042
End Borg	4.3±1.7	3.7±1.8	0.026
SpO2 recovery time, s	64.8±50.0	59.3±46.0	0.457
HR recovery time, s	185.7±97.5	163.4±98.0	0.139
Borg recovery time, s	127.5±56.6	126.5±85.3	0.935

Abbreviations: FiO₂, fraction of inspired oxygen percentage; 6MWD, 6-minute walking distance; start S_pO₂, oxygen saturation measured by pulse oximetry at rest; end S_pO₂, oxygen saturation measured by pulse oximetry at end of walking test; end Borg, Borg score at the end of walking test.

Figure 2 Individual response patterns to ambulatory oxygen.

Abbreviations: 6MWD, 6-minute walking distance; RA, room air.

Table 4 Multivariate Cox proportional hazards model

	P-value	HR	95% CI for HR
			Lower	Upper
6MWD – RA	0.001	0.99	0.993	0.998
Desaturation – RA	0.044	1.05	1.001	1.109
BMI	0.001	0.89	0.834	0.953
Gender (male)	0.009	2.49	1.252	4.934
Hb	0.023	0.80	0.659	0.970
CCI	0.091	1.19	0.973	1.455

Abbreviations: 6MWD, 6-minute walking distance; RA, room air; BMI, body mass index; Hb, blood hemoglobin level; CCI, Charlson comorbidity index.

Figure 3 Kaplan–Meier survival curve.

Note: O₂ responders’ and nonresponders’ survival curves show no significant survival difference (χ²=0.32, P=0.571).