Effects of hyperoxia on oxygen uptake kinetics in cystic fibrosis patientsas determined by pseudo-random binary sequence exercise

Patients with cystic fibrosis (CF) have been shown to exhibit impaired oxyg en uptake ((V) over dot O-2) kinetics independent of their physical fitness . This study investigated whether oxygen supplementation improves (V) over dot O-2 kinetics in CF as determined by cycle ergometry at submaximal exerc ise intensities using a pseudo-random binary sequence exercise test i.e. a simultaneous application of different frequencies of sinusoidal work. The s ubjects were 9 CF patients and 13 healthy controls (HC) and they exercised while breathing humidified and heated air with a fractional concentration o f oxygen in inspired air (FIO2) Of either 0.21 or 0.40. With a FIO2 Of 0.21 the respiratory exchange ratio (R) was higher in CF than in HC both at res t (0.91 vs 0.81) and during exercise (0.97 vs 0.89). Oxygen saturation (SO2 ) was slightly lower in CF, but remained above 90% during exercise (92.7% v s 95.2%. Spectrum analysis revealed that in CF. the amplitude ratio (AR) be tween (V) over dot O-2 and exercise intensity was lower over a wide frequen cy range (P < 0.05). In addition, CF showed a larger negative phase shift ( PS) at lower frequencies (P < 0.005). With a FIO2 of 0.40, SO2 increased to about 97% in both groups. while R remained higher in CF (0.92) compared to HC (0.81). In the control group, the O-2 supplement raised AR but the (V) over dot O-2 kinetics of the CF patients were not significantly affected. I n HC the enhanced AR during oxygen supplementation would suggest a cardiopu lmonary limitation of (V) over dot O-2 at the onset of submaximal exercise. In CF patients low AR and PS would indicate an attenuated (V) over dot O-2 response attributable to an impaired oxygen utilization in the muscles bec ause the oxygen supplement normalised SO2 but failed to improve R and (V) o ver dot O-2 kinetics.