Methodological Quality Of The Work Of Breathing During Exercise: A Systematic Review

Abstract

Measurements of the work of breathing (Wb) during exercise provide useful insights into the energetic demands and mechanics of the respiratory system across a wide range of minute ventilations. The methods used to obtain, compute, and report these Wb measures have yet to be collated and evaluated in the literature. PURPOSE: The aim of this systematic review was to evaluate the quality of methods used to measure Wb during exercise in the published literature. METHODS: An extensive search strategy was designed to retrieve all articles published from database inception until January 12th, 2021, by combining the terms “work of breathing”, “exercise”, “adult humans”, and relevant synonyms in Embase and MEDLINE. Inclusion criteria required articles to be original research with full texts in English, that included measurements of both oesophageal pressure and Wb. Data were extracted on participant characteristics, flow/volume and pressure devices, oesophageal catheters, and Wb measurements. RESULTS: A total of 116 articles were included. Studies predominately investigated healthy individuals (62.9%, N = 73) and used cycling as the primary exercise modality (85.3%, N = 99). The flow sensors used were primarily pneumotachographs (66.4%, N = 83), whereas the most common pressure transducer was of the variable reluctance type (53.0%, N = 61). Oesophageal pressure was most commonly obtained via a balloon-tipped catheter (95.7%, N = 111). 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 (41.4%, N = 48), followed by the Hedstrand (21.6%, N = 25) and Modified Campbell Diagrams (21.6%, N = 25). Over a third of studies did not report the methods used to process their pressure-volume data, and a majority (>64.0%) of studies used the incorrect Wb units and/or failed to discuss the limitations of their Wb measurements. CONCLUSIONS: This review identified a general lack of transparency in the literature, especially regarding device calibration and methods for obtaining Wb measurements. These findings support the development of a standardized approach for measuring Wb that is informative, practical, and accessible for future researchers.