Massin M M, Leclercq-Foucart J, Sacre J P
Division of Pediatric Cardiology, Department of Pediatrics, University of Liege, C.H.R. Citadelle, Boulevard du 12e de Ligne 1, B-4000 Liege, Belgium.
Med Sci Monit. 2000 Jan-Feb;6(1):55-62.
Gas exchange and heart rate (HR) kinetics were investigated in 20 patients with cystic fibrosis (CF) by using a pseudorandom binary sequence (PRBS)-technique. Electrocardiogram was continuously recorded, and VO2, VCO2 and ventilation/min (VE) responses to a multifrequent input signal were measured by means of breath-by-breath analysis. Lag time and peak value in the time-domain, and amplitude ratios in the frequency-domain were calculated to characterize the crosscorrelation functions between input and responses, and compared to normal ranges.
Time and frequency domain parameters are abnormal for VO2, VCO2 and VE responses in moderately and severely ill patients, and for the HR response only in severely ill patients. Correlations are shown between those parameters, the severity of the illness evaluated by the Shwachman score and the level of impairment of the pulmonary function.
The PRBS-technique is a useful tool to investigate the gas exchange and HR kinetics in CF patients, that offers many advantages: (1) no explicit mathematical models are assumed, (2) it is a walking test that may be used even in very young or severely ill patients, and (3) it challenges the ability to adapt to non-steady state exercise and is therefore representative for daily activities.
