Calculation of Breath-by-Breath Oxygen Uptake in Asthmatic Patients by the "Independent Breath" Algorithm. Comparison with a Classical Approach

Several computation algorithms are available to determine gas exchange on a breath-by-breath basis, each designed on the basis of different theoretical backgrounds, including the newly proposed "Independent breath" algorithm. The new algorithm was tested on the respiratory signals acquired from 11 asthmatic patients and 20 well-matched healthy controls, comparing results also with those provided by a "classical" algorithm commonly applied by other laboratories. Oxygen, carbon dioxide fractions, and ventilatory flow were recorded at the mouth continuously over 26 min in all the volunteers at rest, during unloaded and moderate intensity cycling and subsequent recovery. Average oxygen uptake values calculated for the 4 steady-state conditions (over 3 min), as well as the corresponding standard deviations, were not significantly different between the two groups of subjects (MANOVA, Group effect, p = ns). Almost all the average oxygen uptake values provided by the two algorithms were overlapping, the large majority lying within 5% from the identity line. The corresponding standard deviations obtained for the "Independent breath" algorithm were lower than those obtained for the "classical" algorithm (MANOVA, Algorithm effect, p < 0.001), the slope of the regression line between them amounting to 0.672. In conclusion, because of its better precision, with similar accuracy, compared to the "classical" real-time breath-by-breath algorithm, the use of the "Independent breath" algorithm should be recommended, also in asthmatic patients.