Purpose: Breathlessness is a usual ...

Purpose: Breathlessness is a usual complaint and disabling symptom for individuals with chronic obstructive pulmonary disease. Endurance exercise is at short intervals recommended to prevent the consequences of deconditioning and to enable the performance of more activity with les breathlessness. This article reviews the evidence underlying the effectiveness of endurance exercise training in reducing dyspnea in these individuals, and discusses possible mechanisms of dyspnea generation and reduction according to exercise. Summary of Key Points: Findings indicate that endurance exercise is excessively effective at decreasing dyspnea generated during an exercise proof dyspnea during functional activities, and dyspnea affecting the quality of life. During exercise, the severity of dyspnea is related to diffusing capacity of the lung the amount of ventilation required to eliminate carbon dioxide, and the magnitude of dynamic hyperinflation. After endurance exercise training, dyspnea reduction is related to decreased ventilatory demand at submaximal workloads, improvements in VO^sub 2^ workload and, possibly, desensitization to the sensation of dyspnea. Statement of Conclusions: Research supports the routine use of endurance exercise to render dyspnea in individuals with COPD

INTRODUCTION AND PURPOSE

Breathlessness (dyspnea) is a used by all complaint1 and disabling symptom2,3 for individuals with pulmonary disease. Physical therapists encourage these individuals to be active in order to thwart the effects of deconditioning and to enable the performance of activity with les breathlessness. What is the evidence underlying the effectiveness of endurance exercise training in reducing breathlessness, and what is known about the mechanisms which might be responsible for this change? This article describes the definition and measurement of dyspnea and a theory underlying the generation of dyspnea. Possible mechanisms of dyspnea generation and reduction in COPD are discussed, and literature assessing the effectiveness of endurance exercise training in reducing dyspnea is reviewed. The article ends with a brief description of other modalities that have been proven effective and might be used at physical therapists to alter dyspnea in individuals with pulmonary disease.

DEFINITION OF DYSPNEA

Dyspnea is breathing discomfort. A more comprehensive definition was at handed in a recent consensus statement of the American Thoracic Society: "...dyspnea is a mete used to characterize a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. The experience derives from interactions among multiple physiological, psychological, social, and environmental factors, and may induce secondary physiological and behavioral responses"4 The stamp of sensation associated with dyspnea varies, as indicated on the use of particular descriptive words when individuals with dyspnea of different origins are describing their discomfort.5,6 Assessment of dyspnea is tangled encompassing the intensity and quality of the sensation, and the emotional and behavioral answer to the discomfort.4

Measurement of Dyspnea

Various scales are available to measure the relationship between dyspnea and exercise, functional capacity, and quality of life. During exercise testing, the Borg category scale (Borg) and a visual analogue scale (VAS) are commonly used to assess dyspnea. The Borg scale has been shown to be valid and reproducible by means of some investigators,7,8 while others have base that the Borg rating decreases concerning repeated testing in the absence of intervention.9 on comparing Borg ratings of breathlessness in individuals in experimental and reign over groups, this potential problem is diminished. The use of a visual analog scale to assess breathlessness also has been validated and proven reliable in individuals with COPD810 Dyspnea related to functional capacity can be assessed using the Baseline and Transitional Dyspnea Indices and the Chronic Respiratory Disease Questionnaire. The Baseline Dyspnea Index (BDI) evaluates dyspnea related to magnitude of task, magnitude of effort and functional limitation, and the Transitional Dyspnea Index (TDI) assesses improvement or deterioration in each of these parameters. The Chronic Respiratory Disease Questionnaire (CRDQ) is used to measure quality of life by means of assessing 4 domains: dyspnea, emotional function, fatigue, and mastery. The validity and reliability of the couple of these instruments has been established.11-14

HOW DYSPNEA IS GENERATED

Many factors can contribute to the generation of dyspnea and in common individual several factors can be occurring simultaneously. In 1963 Campbell and Howell15 propos that breathlessness could be generated from respiratory muscle "length-tension inappropriateness," which describes a mismatch between the tension generated by the agency of the muscle and the resulting changes in its longitudinal dimensions This initial theory has been broadened to include afferent feedback from manner of makings other than muscle. For example, Schwartzstein et al16 likened dyspnea to the perception of limb muscular effort17 and propos that dyspnea appears when there is a mismatch between the motor command to the respiratory muscles and the eventuate of the command. The motor command is communicated to higher brain center according to corollary discharge (efferent copy) and the resultant output is relayed to the brain by dint of sensory receptors in the airways, lung and chest wall. For example, a particular respiratory motor command should generate a given tidal mass and flow, but sensory receptors may relay signals indicating that the compass and flow that occurred was les than awaited The brain may interpret this efferent-afferent mismatch as breathlessness. Sensory receptors that may be involved in dyspnea generation include put forth receptors, irritant receptors and C fibers in the lung Golgi tendon organs and muscle spindles in the respiratory muscles, and joint receptors in the costal joints. In individuals with hypoxemia, afferent feedback from peripheral chemoreceptors may also play a part in dyspnea generation.18