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Lactate kinetics during exercise in chronic obstructive pulmonary disease: RESULTS (2)

The individual values for b are shown in Figure 1. Parameter b was considerably greater in COPD patients compared with normal subjects (4.49±1.72 versus 2.66±0.47, respectively, P<0.005). As indicated by the dotted line, in 30 of 46 patients, parameter b was greater than the upper value obtained in the normal group.

La/VO2 relationship and the functional class: Peak exercise data obtained for normal subjects and each class of patients are reported in Table 2. In normal subjects, peak VO2 amounted to 32±6 mL/min/kg. In patients the response to exercise was characterized by a rapid increase in symptom scores, a reduced or absent ventilatory reserve, oxygen desaturation and carbon dioxide retention. These abnormalities occurred at a gradually lower exercise work rate with the deterioration in functional status.

Table 2. Peak exercise data in relation to the functional class

Class D (n=8) Class C (n=31) Class B (n=15) Normal subjects (n=10)
VO2 (L/min) 0.62±0.14* 0.89±0.18* 1.31±0.30t 2.18±0.40t
VO2 (mL/min/kg) 8.7±0.9t 13.0±1.5t 18.0±1.5t 31.7±6.4t
VCO2 (L/min) 0.51±0.11* 0.80±0.19* 1.30±0.37t 2.39±0.48t
Heart rate (beats/min) 119±16* 128±15* 138±10§ 158±8t
Heart rate (% maximum) 72±11* 76±9* 83±5§ 95±5t
VE (L/min) 22±5* 33±8* 45±15§ 93±26t
VE/MVV (%) 94±15 107±21 106±24 91±25
Borg score
Dyspnea 7.2±2.0T 8.3±1.6t 7.9±2.2t 5.5±2.0§
Leg fatigue 4.2±4.3 7.1±2.6 6.3±3.0 5.6±2.8
PaO2 (mmHg) 61±14* 65±10t 72±13** 100±12t
Oxygen saturation (%) 88±7t 90±6t 92±5t 98±1§
pH 7.32±0.01 7.34±0.04 7.32±0.04 7.35±0.04
PCO2 (mmHg) 56±5§ 49±7** 49±6** 36±5t

All values mean ±SD. *P<0.01 versus any other group; TP<0.001 versus any other group; fP< 0.05 versus class Band normal subjects; §P<0.05 versus any other group; *P<0.05 versus normal subjects; **P<0.05 versus class D and normal subjects. MVV Maximum voluntary ventilation; VO2 Oxygen uptake; VCO2 Carbon dioxide output; Ve Minute ventilation


Category: Pulmonary disease

Tags: Chronic obstructive pulmonary disease, Exercise, Lactate

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