Acidosis and raised norepinephrine levels are associated with exercise dyspnoea in idiopathic pulmonary fibrosis.
OBJECTIVE
Exertional dyspnoea limits patients with IPF in their activities of daily living. The mechanism, however, has not been elucidated. This study tested the hypothesis in IPF that exertional dyspnoea correlates with cardiopulmonary exercise responses, specifically changes in arterial blood pH and plasma norepinephrine (NE).


METHODS
Cardiopulmonary exercise testing with measurements of dyspnoea (Borg scale), plasma NE, plasma lactate and arterial blood gases were performed in 29 patients with IPF and in nine controls.


RESULTS
Both groups showed obvious break points in dyspnoea changes during exercise. In IPF, an abrupt change in the Borg scale, pH, PaCO(2) and plasma NE occurred in the late exercise phase after the 'break point'. Compared with controls, patients with IPF had significantly higher HCO(3)(-) levels and physiologic dead space/tidal volume during exercise. In IPF, during both exercise phases, the dyspnoea slope (DeltaBorg scale/Deltaminute ventilation) correlated with the pH slope (DeltapH/Deltaoxygen uptake) (before the break point: r = -0.537, P = 0.0022; r = -0.886, P < 0.0001, after the break point) and the NE slope (DeltaNE/Deltaoxygen uptake) (before the break point: r = 0.481, P = 0.0075; R = 0.784, P < 0.0001, after the break point).


CONCLUSIONS
In patients with IPF, exercise-induced acidosis and increases in circulating NE levels were associated with intensity of exertional dyspnoea.
Miki
Keisuke
K
Department of Internal Medicine, National Hospital Organization Toneyama National Hospital, Toyonaka, Osaka, Japan. mikisuke@toneyama.go.jp
Maekura
Ryoji
R
Hiraga
Toru
T
Hashimoto
Hisako
H
Kitada
Seigo
S
Miki
Mari
M
Yoshimura
Kenji
K
Tateishi
Yoshitaka
Y
Fushitani
Kenji
K
Motone
Masaharu
M
D000138:Acidosis / Q000097:blood*; D000368:Aged; D000369:Aged, 80 and over; D001784:Blood Gas Analysis; D016022:Case-Control Studies; D004417:Dyspnea / Q000097:blood* / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D054990:Idiopathic Pulmonary Fibrosis / Q000097:blood* / Q000503:physiopathology*; D007773:Lactates / Q000097:blood; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood*; D012129:Respiratory Function Tests
D007773:Lactates; D009638:Norepinephrine