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

INTRODUCTION: Measurement 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. PURPOSE: The aim of this systematic review was to evaluate the quality of methods used to measure the Wb during exercise in the available literature. METHODS: We 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. RESULTS: A 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. CONCLUSIONS: The 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.

The Influence of Social Distancing Behaviors and Psychosocial Factors on Physical Activity During the COVID-19 Pandemic: Cross-sectional Survey Study.

BACKGROUND: The COVID-19 pandemic has arguably facilitated a shift toward increased sedentariness and reduced physical activity. Moreover, there is mounting evidence that mental health has also declined during the pandemic. However, it remains unknown to what extent social distancing (SD) behaviors and mental health have affected the physical activity levels of the general population. OBJECTIVE: The purpose of this study was to determine the influence of SD behaviors and prevailing mental health on the odds of being physically active during the early COVID-19 pandemic response. METHODS: A total of 4819 adults (2474/4819, 51.3%, female) from the US population with a median age of 46 (IQR 35-59) completed an online survey during the early pandemic response (April-June 2020). The survey included questions on adherence to 11 SD behaviors, and validated questionnaires which assessed self-reported physical activity, depression, anxiety, and mental well-being. Respondents were categorized into 2 physical activity groups: inactive (0-599 metabolic equivalent of task [MET]-minutes/week) and active (≥600 MET-minutes/week). A logistic generalized additive model (GAM) was used to determine which SD factors and mental health outcomes were associated with physical activity level. RESULTS: The GAM analysis revealed that wearing a facemask in public (odds ratio [OR] 1.46, 95% CI 1.14-1.79; P=.003), limiting the use of public transport (OR 1.47, 95% CI 1.19-1.83; P=.001), and restricting travel outside the house (OR 1.56, 95% CI 1.19-2.05; P=.002) were SD behaviors associated with higher odds of being more physically active. Conversely, avoiding physical activity outside the house was associated with higher odds of being inactive (OR 0.52, 95% CI 0.46-0.63; P<.001). Leaving the house more frequently, and a higher mental well-being were associated with increasing odds of being physically active (P<.001). Engaging with a moderate number of SD behaviors (3-7 total) was positively associated with physical activity, whereas a very high SD vigilance (ie, engaging with ≥10 total behaviors) decreased the odds of being active during the early pandemic response. CONCLUSIONS: Based on the findings of our study, we suggest that future public health messaging of SD guidelines should include (1) a clear portrayal of the benefits of regular exercise on mental health; and (2) a specific focus on how to be physically active outdoors in a COVID-safe manner.

A comparison of methods used to quantify the work of breathing during exercise.

The mechanical work of breathing (Wb) is an insightful tool used to assess respiratory mechanics during exercise. There are several different methods used to calculate the Wb, however, each approach having its own distinct advantages/disadvantages. To date, a comprehensive assessment of the differences in the components of Wb between these methods is lacking. We therefore sought to compare the values of Wb during graded exercise as determined via the four most popular methods: 1) pressure-volume integration; 2) the Hedstrand diagram; 3) the Otis diagram; and the 4) modified Campbell diagram. Forty-two participants (30 ± 15 yr; 16 women) performed graded cycling to volitional exhaustion. Esophageal pressure-volume loops were obtained throughout exercise. These data were used to calculate the total Wb and, where possible, its subcomponents of inspiratory and expiratory, resistive and elastic Wb, using each of the four methods. Our results demonstrate that the components of Wb were indeed different between methods across the minute ventilations engendered by graded exercise. Importantly, however, no systematic pattern in these differences could be observed. Our findings indicate that the values of Wb obtained during exercise are uniquely determined by the specific method chosen to compute its value-no two methods yield identical results. Because there is currently no "gold-standard" for measuring the Wb, it is emphasized that future investigators be cognizant of the limitations incurred by their chosen method, such that observations made by others may be interpreted with greater context, and transparency.NEW & NOTEWORTHY The measurement of the work of breathing (Wb) during exercise provides us with deep insights into respiratory (patho)physiology, and sheds light on the putative factors which lead to respiratory muscle fatigue. There are 4 popular methods available to determine the Wb. Our study demonstrates that no two of these methods produce identical values of Wb during exercise. This paper also discusses the practical and theoretical limitations of each method.