Effects of oxygen on exertional dyspnoea and exercise performance in patients with chronic obstructive pulmonary disease.
OBJECTIVE
The results of studies on the oxygen response in patients with COPD should provide important clues to the pathophysiology of exertional dyspnoea. We investigated the exercise responses to hyperoxia in relation to dyspnoea profile, as well as cardiopulmonary, acidotic and sympathetic parameters in 35 patients with stable COPD (mean FEV(1) 46% predicted).


METHODS
This was a single-blind trial, in which patients breathed 24% O(2) or compressed air (CA) in random order during two incremental cycle exercise tests.


RESULTS
PaO(2) and PaCO(2) were higher (P < 0.0001 and P < 0.05, respectively) at each exercise point while patients were breathing 24% O(2) compared with CA. At a standardized time point near peak exercise, use of O(2) resulted in reduced plasma lactate and plasma noradrenaline concentrations (P < 0.01). Peak minute ventilation/indirect maximum voluntary ventilation was similar while breathing 24% O(2) and CA. At peak exercise, the dyspnoea score, pH and plasma noradrenaline concentrations were similar while breathing 24% O(2) and CA. The dyspnoea-ratio (%) of Δoxygen uptake (peak minus resting oxygen uptake) curve reached a break point that occurred at a similar exercise point while breathing 24% O(2) or CA.


CONCLUSIONS
Regardless of whether they breathed CA or 24% O(2) , patients with COPD did not develop ventilatory compensation for exertional acidosis, and the pH values measured were similar. Hyperoxia during a standardized exercise protocol did not alter the pattern of exertional dyspnoea in these patients, compared with breathing CA, although hyperoxia resulted in miscellaneous effects.
Department of Internal medicine, National Hospital Organization Toneyama National Hospital, Toyonaka, Osaka, Japan. mikisuke@toneyama.go.jp
Keisuke
K
Miki
Ryoji
R
Maekura
Toru
T
Hiraga
Seigo
S
Kitada
Mari
M
Miki
Kenji
K
Yoshimura
Yoshitaka
Y
Tateishi
D000138:Acidosis / Q000097:blood*; D000368:Aged; D001784:Blood Gas Analysis; D004417:Dyspnea / Q000097:blood* / Q000503:physiopathology; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018496:Hyperoxia / Q000097:blood* / Q000503:physiopathology; D007773:Lactates / Q000097:blood*; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D005082:Physical Exertion; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000503:physiopathology; D016037:Single-Blind Method
D007773:Lactates; D010100:Oxygen