Breath‐by‐breath pulmonary O2 uptake kinetics: effect of data processing on confidence in estimating model parameters. Issue 11 (8th October 2014)

• Record Type: Journal Article
• Authors: Keir, Daniel A.; Murias, Juan M.; Paterson, Donald H.; Kowalchuk, John M.
• Is Part Of: Experimental physiology. Volume 99:Issue 11(2014:Nov.)
• Page Start: 1511
• Page End: 1522
• Publication Date: 2014-10-08
• Subjects: Physiology, Experimental -- Periodicals; 571.0724
• DOI: 10.1113/expphysiol.2014.080812
• Languages: English
• ISSNs: 0958-0670

Abstract

<abstract abstract-type="main"> <title>New Findings</title> <sec id="eph1493-sec-0010" sec-type="section"> <p> <list id="eph1493-list-0001" list-type="bullet"> <list-item> <p> <bold>What is the central question of this study?</bold> </p> <p>In groups of young and older adults, we investigated whether techniques used as common practice for processing breath‐by‐breath pulmonary O<sub>2</sub> 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<sub>2</sub> uptake response.</p> </list-item> <list-item> <p> <bold>What is the main finding and its importance?</bold> </p> <p>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<sub>2</sub> uptake response; however, the confidence in the parameter estimation could be improved by the technique used to process individual trials.</p> </list-item> </list> </p> </sec> <sec id="eph1493-sec-0020" sec-type="section"> <p>To improve the signal‐to‐noise ratio of breath‐by‐breath pulmonary O<sub>2</sub> uptake (<inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh06tz" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula>) 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 II <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh06w2" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0002" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> kinetic parameter estimates (<inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh071s" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0003" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> amplitude, time delay and phase II time constant (<italic>τ</italic><inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh072b" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0004" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula>)] and model confidence [95% confidence interval (CI<sub>95</sub>)] was examined. Young (<italic>n</italic> = 9) and older men (<italic>n</italic> = 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‐breath <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh06xm" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0005" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> was measured using mass spectrometry and volume turbine. Mono‐exponential kinetic modelling of phase II <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh06z5" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0006" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> data 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<sub>95</sub> for <italic>τ</italic><inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh0773" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0007" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> in condition 'D' (4 s) was lower (<italic>P</italic> < 0.05) than the CI<sub>95</sub> reported for all other conditions (5–10 s). Data‐processing technique had no effect on parameter estimates of the phase II <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh22bh0796" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1493:equation:eph1493-math-0008" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>̇</mml:mo></mml:mover><mml:mrow><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">p</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> response. However, the narrowest interval for CI<sub>95</sub> occurred when individual trials were linearly interpolated and ensemble averaged.</p> </sec> </abstract>