Exercise Endurance in Chronic Obstructive Pulmonary Disease Patients at an Altitude of 2640 meters Breathing Air and Oxygen (FIO2 28% and 35%): A Randomized Crossover Trial

Figures & data

Table 1.  Subjects characteristics (N = 29)

Parameter	Value
Age, yr	66.5 ± 6.6
Body mass index, kg/m^2	24.2 ± 3.3
Smoking, pack-year	43.6 ± 28.4
MRC dyspnea scale (1–5)	2.4 ± .74
Hemoglobin, gr/dl	16.0 ± 1.8
Pulmonary Function
FVC,% predicted	86.2 ± 18.6
FEV1,% predicted	42.9 ± 11.9
FEV1/FVC,%	40.1 ± 10.5
TLC,% predicted	122.1 ± 20.3
FRC,% predicted	175.1 ± 38.1
RV,% predicted	212.0 ± 56.6
RV/TLC,%	62.9 ± 7.7
IC,% predicted	70.7 ± 14.7
DLCO,% predicted	53.1 ± 15.3
Arterial blood gases (at rest - room air)
PaO2, mmHg	50.8 ± 6.6
SaO2,%	85.7 ± 5.6
SpO2,%	85.4 ± 4.6
PaCO2, mmHg	34.7 ± 4.4
pH	7.40 ± .03
HCO3, meq/L	21.4 ± 2.3
P(A-a)O2	16.4 ± 5.9

MRC: Medical Research Council; FVC: forced vital capacity; FEV₁: forced expiratory volume in 1s; TLC: total lung capacity; FRC: functional residual capacity; RV: residual volume; IC: inspiratory capacity; DLCO: lung diffusing capacity for carbon monoxide; PaO₂: oxygen arterial pressure; SaO₂: arterial oxygen saturation; SpO₂: Pulse oximetry; PaCO₂: carbon dioxide arterial pressure; HCO3: bicarbonate; P(A-a)O₂: alveolar-arterial oxygen pressure difference. Values: mean ± SD.

Table 2.  Variables at the end of symptom-limited endurance tests

Parameter	FIO2 21%	FIO2 28%	FIO2 35%
Dyspnea, Borg scale	5.5 ± 2.5	6.0 ± 3.1	5.7 ± 2.6
Leg discomfort, org scale	4.8 ± 2.8	4.9 ± 3.2	4.8 ± 2.8
VO2, ml/min	1086.8 ± 482.6*	1261.2 ± 429.5	1374.2 ± 535.0
VCO2, ml/min	1078.0 ± 476.9	1105.5 ± 381.1	1072.7 ± 389.8
HR, beats/min	132.0 ± 18.6*	128.5 ± 19.6	126.5 ± 18.8
O2 pulse, ml O2/beat	8.2 ± 3.2*	9.8 ± 2.7	10.9 ± 3.8
VE, L/min	38.3 ± 12.7	36.9 ± 10.2	35.2 ± 10.3
VT, ml	1121.2 ± 278.5	1143.5 ± 252.9	1104.4 ± 218.7
fR, breaths/min	34.1 ± 7.0	32.4 ± 6.6	31.8 ± 6.0
VE/MVV,%	77.2 ± 15.2	75.1 ± 13.8	72.3 ± 16.7
Delta CI, L	–0.544 ± .257	–0.512 ± 0.207	–0.480 ± 0.236
PaCO2, mmHg	38.4 ± 5.5	40.6 ± 6.3	41.2 ± 6.6
PaO2, mmHg	46.5 ± 8.2 &*	71.1 ± 12.9	94.5 ± 17.3 £
SaO2,%	77.6 ± 10.3 &*	91.4 ± 6.5	95.8 ± 3.4 £
pH	7.32 ± 0.05	7.32 ± 0.05	7.32 ± 0.05
HCO3	19.7 ± 2.0	20.6 ± 2.3	20.9 ± 2.4
CaO2, ml	17.0 ± 2.4 &*	20.0 ± 2.2	20.9 ± 2.2
Delta lactate, mmol/L	2.39 ± 1.71 &*	1.14 ± 1.79	0.77 ± 1.62

VO₂: oxygen uptake; VCO₂: carbon dioxide output; HR: heart rate; VE: minute ventilation; VT: tidal volume; fR: respiratory frequency; MVV: maximal voluntary respiration; IC: inspiratory capacity; PaO₂: oxygen arterial pressure; PaCO₂: carbon dioxide arterial pressure; HCO3: bicarbonate; SaO₂: oxygen arterial saturation; CaO₂: arterial oxygen content.

Values: mean ± SD

&: p < 0.05 21% vs. 28%; *: p < 0.05 21% vs. 35%; £: p < 0.05 28% vs. 35%

Figure 1.  Endurance time with air and oxygen. There was a significant increase in exercise duration with supplemental oxygen, without differences between FIO₂ 28% and 35% (p < 0.001 21% vs. 28% and 21% vs. 35%, p = 0.22 28% vs. 35%). FIO₂: inspired oxygen fraction. Bars represent CI95%.

Table 3.  Variables at the endurance exercise isotime

	FIO2 21%	FIO2 28%	FIO2 35%
VO2, mL/min	1086.8 ± 482.6	1224.3 ± 497.5	1363.5 ± 619.9
VCO2, ml/min	1078.0 ± 476.9	1018.1 ± 393.9	975.8 ± 400.3
Dyspnea, Borg scale	5.5 ± 2.5	4.5 ± 2.5	4.3 ± 2.5
Leg discomfort, Borg scale	4.8 ± 2.8	3.8 ± 2.7	3.5 ± 2.1
HR, beats/min	132.0 ± 18.6 &*	120.9 ± 17.2	119.2 ± 20.4
O2 pulse, ml O2/beat	8.2 ± 3.2 &*	10.1 ± 3.5	11.5 ± 4.9
SpO2,%	72.6 ± 6.8 &*	87.2 ± 6.1	93.0 ± 3.7 £
VE, L	38.3 ± 12.7	35.1 ± 10.3	33.5 ± 10.8
VT, ml	1121.2 ± 278.5	1172.2 ± 233.7	1160.3 ± 276.0
fR, breaths/min	34.1 ± 7.0 &*	30.0 ± 6.6	29.1 ± 7.1
VE/MVV,%	77.2 ± 15.2 *	70.5 ± 10.7	67.6 ± 13.7
Delta CI, L	0.544 ± 0.257 &*	0.399 ± 0.201	0.362 ± 0.201

Isotime: time at which the room air test ended; SpO₂: pulse oximetry; VE: minute ventilation; VT: tidal volume; MVV: maximal voluntary ventilation; IC: inspiratory capacity.

Values are means ± SD.

&: p < 0.05 21% vs. 28%; *: p < 0.05 21% vs. 35%; £: p < 0.05 28% vs. 35%