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Emerging Concepts in the Evaluation of Ventilatory Limitation During Exercise

1999; Elsevier BV; Volume: 116; Issue: 2 Linguagem: Inglês

10.1378/chest.116.2.488

1931-3543

Bruce D. Johnson, Idelle M. Weisman, R. Jorge Zeballos, Ken C. Beck,

Respiratory Support and Mechanisms

Traditionally, ventilatory limitation (constraint) during exercise has been determined by measuring the ventilatory reserve or how close the minute ventilation (e) achieved during exercise (ie, ventilatory demand) approaches the maximal voluntary ventilation (MVV) or some estimate of the MVV (ie, ventilatory capacity). More recently, it has become clear that rarely is the MVV breathing pattern adopted during exercise and that the e/MVV relationship tells little about the specific reason(s) for ventilatory constraint. Although it is not a new concept, by measuring the tidal exercise flow-volume (FV) loops (extFVLs) obtained during exercise and plotting them according to a measured end-expiratory lung volume (EELV) within the maximal FV envelope (MFVL), more specific information is provided on the sources (and degree) of ventilatory constraint. This includes the extent of expiratory flow limitation, inspiratory flow reserve, alterations in the regulation of EELV (dynamic hyperinflation), end-inspiratory lung volume relative to total lung capacity (or tidal volume/inspiratory capacity), and a proposed estimate of ventilatory capacity based on the shape of the MFVL and the breathing pattern adopted during exercise. By assessing these types of changes, the degree of ventilatory constraint can be quantified and a more thorough interpretation of the cardiopulmonary exercise response is possible. This review will focus on the potential role of plotting the extFVL within the MFVL for determination of ventilatory constraint during exercise in the clinical setting. Important physiologic concepts, measurements, and limitations obtained from this type of analysis will be defined and discussed. Traditionally, ventilatory limitation (constraint) during exercise has been determined by measuring the ventilatory reserve or how close the minute ventilation (e) achieved during exercise (ie, ventilatory demand) approaches the maximal voluntary ventilation (MVV) or some estimate of the MVV (ie, ventilatory capacity). More recently, it has become clear that rarely is the MVV breathing pattern adopted during exercise and that the e/MVV relationship tells little about the specific reason(s) for ventilatory constraint. Although it is not a new concept, by measuring the tidal exercise flow-volume (FV) loops (extFVLs) obtained during exercise and plotting them according to a measured end-expiratory lung volume (EELV) within the maximal FV envelope (MFVL), more specific information is provided on the sources (and degree) of ventilatory constraint. This includes the extent of expiratory flow limitation, inspiratory flow reserve, alterations in the regulation of EELV (dynamic hyperinflation), end-inspiratory lung volume relative to total lung capacity (or tidal volume/inspiratory capacity), and a proposed estimate of ventilatory capacity based on the shape of the MFVL and the breathing pattern adopted during exercise. By assessing these types of changes, the degree of ventilatory constraint can be quantified and a more thorough interpretation of the cardiopulmonary exercise response is possible. This review will focus on the potential role of plotting the extFVL within the MFVL for determination of ventilatory constraint during exercise in the clinical setting. Important physiologic concepts, measurements, and limitations obtained from this type of analysis will be defined and discussed. Tidal Flow-Volume Analysis of Ventilation During Exercise: A Useful Approach for Diagnosing the Mechanism of Ventilatory Limitation to Exercise During Cardiopulmonary Exercise TestingCHESTVol. 116Issue 2PreviewAt the present time, the diagnosis of a ventilatory limitation to exercise is based on the breathing reserve concept, ie, how close the peak exercise ventilation (Ve) approaches the maximum voluntary ventilation (MVV) or some estimate of the MVV (typically the FEV1 multiplied by 35 or 40). Therefore, a small or no breathing reserve indicates a Ve limitation to muscular exercise (Ve limit), whereas a large breathing reserve rules out a Ve limit. At a given intensity of external work, the four major causes of an increased Ve—and therefore, a decreased breathing reserve—are some combination of the following: (1) arterial hypoxemia; (2) arterial acidosis effected by increases in lactate concentration; (3) anxiety and phobias regarding exercise and/or sensations related to it; and (4) inefficiency in performing a particular type of exercise. Full-Text PDF