TY - JOUR
T1 -
Role of CO
2
responsiveness and breathing efficiency in determining exercise capacity of patients with chronic airway obstruction
AU - Chonan, T.
AU - Hida, W.
AU - Kikuchi, Y.
AU - Shindo, Chiyohiko
AU - Takishima, T.
PY - 1988/1/1
Y1 - 1988/1/1
N2 -
We examined the role of CO
2
responsiveness and breathing efficiency in limiting exercise capacity in 15 patients with chronic airway obstruction (FEV
1
= 0.88 ± 0.25 L, mean ± SD). Responses of minute ventilation and P
0.1
(mouth pressure 0.1 s after the onset of occluded inspiration) to hypercapnia (ΔV̇E/ΔPCO
2
, ΔP
0.1
/ΔPCO
2
) were measured by rebreathing, and the ratio of the two (ΔV̇E/ΔP
0.1
) was defined as an index of breathing efficiency during hyperventilation. Exercise capacity was measured as symptom-limited, maximal oxygen consumption (V̇O
2
max/BW) in an incremental treadmill test and also as the 12-min walking distance (TMD). All patients discontinued the treadmill test because of dyspnea, and the exericse capacity correlated with the degree of airway obstruction, although there was a wide variability among patients with comparable FEV
1
. There were no significant correlations between the responses to CO
2
and exercise capacity. However, there was a significant correlation between ΔV̇E/ΔP
0.1
and V̇O
2
max/BW (r = 0.87, p < 0.001) or TMD (r = 0.78, p < 0.001), and these correlations remained significant even when the relational effects of FEV
1
were taken out. These results support the hypothesis that airway obstruction and breathing efficiency are important, but that CO
2
responsiveness is not a major factor in determining the exercise capacity of patients with chronic airway obstruction.
AB -
We examined the role of CO
2
responsiveness and breathing efficiency in limiting exercise capacity in 15 patients with chronic airway obstruction (FEV
1
= 0.88 ± 0.25 L, mean ± SD). Responses of minute ventilation and P
0.1
(mouth pressure 0.1 s after the onset of occluded inspiration) to hypercapnia (ΔV̇E/ΔPCO
2
, ΔP
0.1
/ΔPCO
2
) were measured by rebreathing, and the ratio of the two (ΔV̇E/ΔP
0.1
) was defined as an index of breathing efficiency during hyperventilation. Exercise capacity was measured as symptom-limited, maximal oxygen consumption (V̇O
2
max/BW) in an incremental treadmill test and also as the 12-min walking distance (TMD). All patients discontinued the treadmill test because of dyspnea, and the exericse capacity correlated with the degree of airway obstruction, although there was a wide variability among patients with comparable FEV
1
. There were no significant correlations between the responses to CO
2
and exercise capacity. However, there was a significant correlation between ΔV̇E/ΔP
0.1
and V̇O
2
max/BW (r = 0.87, p < 0.001) or TMD (r = 0.78, p < 0.001), and these correlations remained significant even when the relational effects of FEV
1
were taken out. These results support the hypothesis that airway obstruction and breathing efficiency are important, but that CO
2
responsiveness is not a major factor in determining the exercise capacity of patients with chronic airway obstruction.
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U2 - 10.1164/ajrccm/138.6.1488
DO - 10.1164/ajrccm/138.6.1488
M3 - Article
C2 - 3144217
AN - SCOPUS:0024165254
VL - 138
SP - 1488
EP - 1493
JO - American Journal of Respiratory and Critical Care Medicine
JF - American Journal of Respiratory and Critical Care Medicine
SN - 1073-449X
IS - 6
ER -