Oxygen uptake kinetics are slowed in cystic fibrosis.
OBJECTIVE
There are conflicting reports on the kinetics of oxygen uptake at the onset of exercise in patients with cystic fibrosis (CF). The objective of the present study was, therefore, to compare oxygen uptake (VO(2) kinetics in patients with CF with those of healthy controls (CON).


METHODS
Eighteen CF patients (FEV1 37-98% predicted) and 15 CON aged 10-33 yr completed two to four transitions from low-intensity cycling (stage 1, 20 W) to cycling at 1.3-1.4 W.kg(-1) body weight (stage 2). There was no difference between groups in heart rate at stages 1 and 2 or in relative exercise intensity, as expressed as percent VO(2peak) or percentage of ventilatory threshold. However, oxygen saturation (SpO(2)) was lower in the patients with CF during both stages. VO(2) data were interpolated second by second, time-aligned, and averaged. Monoexponential equations were used to describe phase II VO(2) responses.


RESULTS
Although there were no differences between CF and CON in amplitude (10.9 +/- 1.8 vs 10.2 +/- 1.6 mL O2.W(-1)) of phase II VO(2) response, the time constant tau was significantly prolonged in CF compared with CON (36.8 +/- 13.6 vs 26.4 +/- 9.1 s). When tau was adjusted for the effects of FEV1 or SpO(2) during submaximal exercise, the difference between CF patients and controls disappeared.


CONCLUSIONS
VO(2) kinetics are slowed in CF, which may, in part, be attributed to an impairment of oxygen delivery.
Hebestreit
Helge
H
Department of Pediatrics, Julius-Maximilians University, 97080 Würzburg, Germany. hebestreit@mail.uni-wuerzburg.de
Hebestreit
Alexandra
A
Trusen
Andreas
A
Hughson
Richard L
RL
D000293:Adolescent; D000328:Adult; D002648:Child; D003550:Cystic Fibrosis / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D012129:Respiratory Function Tests; D013997:Time Factors