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)|
|Heart rate (beats/min)||119±16*||128±15*||138±10§||158±8t|
|Heart rate (% maximum)||72±11*||76±9*||83±5§||95±5t|
|Oxygen saturation (%)||88±7t||90±6t||92±5t||98±1§|
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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