A Systematic Review of Methods Used to Determine the Work of Breathing during Exercise

IntroductionMeasurement of the work of breathing (Wb) during exercise provides useful insights into the energetics and mechanics of the respiratory muscles across a wide range of minute ventilations. The methods and analytical procedures used to calculate the Wb during exercise have yet to be critically appraised in the literature.PurposeThe aim of this systematic review was to evaluate the quality of methods used to measure the Wb during exercise in the available literature.MethodsWe conducted an extensive search of three databases for studies that measured the Wb during exercise in adult humans. Data were extracted on participant characteristics, flow/volume and pressure devices, esophageal pressure (P-oes) catheters, and methods of Wb analysis.ResultsA total of 120 articles were included. Flow/volume sensors used were primarily pneumotachographs (n = 85, 70.8%), whereas the most common pressure transducer was of the variable reluctance type (n = 63, 52.5%). Esophageal pressure was frequently obtained via balloon-tipped catheters (n = 114, 95.0%). Few studies mentioned calibration, frequency responses, and dynamic compensation of their measurement devices. The most popular method of measuring the Wb was pressure-volume integration (n = 51, 42.5%), followed by the modified Campbell (n = 28, 23.3%) and Dean & Visscher diagrams (n = 26, 21.7%). Over one-third of studies did not report the methods used to process their pressure-volume data, and the majority (60.8%) of studies used the incorrect Wb units and/or failed to discuss the limitations of their Wb measurements.ConclusionsThe findings of this systematic review highlight the need for the development of a standardized approach for measuring Wb, which is informative, practical, and accessible for future researchers.