Chest
ReviewsEmerging Concepts in the Evaluation of Ventilatory Limitation During Exercise: The Exercise Tidal Flow-Volume Loop
Section snippets
Information Gained From the extFVL/MFVL Analysis
By aligning the extFVL within the MFVL, specific information is provided on the following: (1) the degree of expiratory flow limitation; (2) breathing strategy (ie, changes in EELV); (3) elastic load, as represented by the EILV as a percent of TLC (EILV/TLC) or the tidal volume (Vt) relative to inspiratory capacity (IC); (4) inspiratory flow reserve; and (5) a theoretical estimate of the ventilatory capacity based on the EELV and the maximal expiratory/inspiratory flows available over the range
The Traditional View of Ventilatory Limitation
The traditional use of the MVV or some estimate of the MVV such as the FEV1 multiplied by 35 or 40 relative to the exercise ventilation as an assessment of breathing reserve has several advantages. It provides a general (although variable) approximation of ventilatory capacity, it is readily and widely applied, it is easily understood, and it requires minimal analysis. However, the use of the MVV to estimate the available ventilatory capacity during exercise and to determine whether or not
Assessing Ventilatory Constraint Using the extFVL
As the sophistication of conventional exercise systems improve, it will become easier to measure and to assess the degree of flow limitation as well as changes in EELV and EILV, with minimal changes in the standard clinical exercise protocol. Conventional exercise metabolic systems have evolved using the pneumotachograph, hot wire anemometer, and turbine (bi-directional rotating vane) technology that provide software to evaluate tidal breathing FV loops relative to a MFVL. Although there are
Exercise Patterns in Health And Disease
The following section will review the tidal FV responses to exercise in various representative clinical examples contrasted with responses observed in the healthy young and older adults. It should be emphasized that the degree of ventilatory constraint is indeed a balance between ventilatory demands and the available capacities. Thus, even the healthy young adult may approach severe ventilatory limitations, albeit at a metabolic and ventilatory demand that far exceeds the patient populations.
Current and Future Aims
Over the last 30 years, little progress has been made in the typical clinical setting in trying to better define mechanisms of exercise intolerance and dyspnea, particularly when associated with the possibility of mechanical constraints imposed by the respiratory system. The classic MVV, while easily applied, is variable and has proved to be limited in its overall usefulness of advancing our understanding of ventilatory limitation during exercise. As such, investigational studies have attempted
Measurement of the extFVL
Most clinical exercise testing laboratories today employ automated systems for measurement of gas exchange during exercise (eg, e, o2, and carbon dioxide production). The majority of these systems use a device for measuring flow (eg, pneumotachograph, mass-flow anemometer, turbine) and integrate a flow signal to obtain volume. Few of these automated systems, until recently, have offered continuous output of flow and volume in order to obtain the tidal FV data necessary for plotting the tidal
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2023, Respiratory Physiology and NeurobiologyExertional Dyspnoea responses reported in the Dyspnoea Challenge and measures of disease severity in COPD
2022, Respiratory Physiology and NeurobiologyCitation Excerpt :Our results could have been impacted by a desensitisation effect and may not be applicable to individuals with COPD who have not completed a rehabilitation programme. Estimations of breathing reserve using V̇E/MVV have been criticised as MVV may not represent a realistic physiological measure of maximal ventilatory output during exercise (Klas and Dempsey, 1989), it does not provide insight on breathing strategy or the degree of respiratory flow constraints (Johnson et al., 1999). However, this measure is common place in clinical settings and is still recommended for assessing the mechanisms of a patient's dyspnoea (Guazzi et al., 2012).