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Breath‐by‐breath pulmonary O 2 uptake kinetics: effect of data processing on confidence in estimating model parameters
Author(s) -
Keir Daniel A.,
Murias Juan M.,
Paterson Donald H.,
Kowalchuk John M.
Publication year - 2014
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2014.080812
Subject(s) - confidence interval , kinetics , chemistry , medicine , physics , quantum mechanics
New FindingsWhat is the central question of this study? In groups of young and older adults, we investigated whether techniques used as common practice for processing breath‐by‐breath pulmonary O 2 uptake data from repeated step transitions in work rate into the moderate‐intensity exercise domain influence the model parameter estimations and confidence of describing the phase II pulmonary O 2 uptake response.What is the main finding and its importance? Results demonstrate that regardless of age group, during transitions into the moderate‐intensity exercise domain, techniques for processing individual transitions did not affect parameter estimates describing the phase II pulmonary O 2 uptake response; however, the confidence in the parameter estimation could be improved by the technique used to process individual trials.Abstract To improve the signal‐to‐noise ratio of breath‐by‐breath pulmonary O 2 uptake ( V ̇O 2 p ) data, it is common practice to perform multiple step transitions, which are subsequently processed to yield an ensemble‐averaged profile. The effect of different data‐processing techniques on phase IIV ̇O 2 pkinetic parameter estimates ( V ̇O 2 pamplitude, time delay and phase II time constant ( τV ̇O 2 p )] and model confidence [95% confidence interval (CI 95 )] was examined. Young ( n = 9) and older men ( n = 9) performed four step transitions from a 20 W baseline to a work rate corresponding to 90% of their estimated lactate threshold on a cycle ergometer. Breath‐by‐breathV ̇O 2 pwas measured using mass spectrometry and volume turbine. Mono‐exponential kinetic modelling of phase IIV ̇O 2 pdata was performed on data processed using the following techniques: (A) raw data (trials time aligned, breaths of all trials combined and sorted in time); (B) raw data plus interpolation (trials time aligned, combined, sorted and linearly interpolated to second by second); (C) raw data plus interpolation plus 5 s bin averaged; (D) individual trial interpolation plus ensemble averaged [trials time aligned, linearly interpolated to second by second (technique 1; points joined by straight‐line segments), ensemble averaged]; (E) ‘D’ plus 5 s bin averaged; (F) individual trial interpolation plus ensemble averaged [trials time aligned, linearly interpolated to second by second (technique 2; points copied until subsequent point appears), ensemble averaged]; and (G) ‘F’ plus 5 s bin averaged. All of the model parameters were unaffected by data‐processing technique; however, the CI 95 for τV ̇O 2 pin condition ‘D’ (4 s) was lower ( P < 0.05) than the CI 95 reported for all other conditions (5–10 s). Data‐processing technique had no effect on parameter estimates of the phase IIV ̇O 2 presponse. However, the narrowest interval for CI 95 occurred when individual trials were linearly interpolated and ensemble averaged.