Effects of Obesity in the Aged

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PROJECT SUMMARY/ABSTRACT Seventy% of older adults (60+ yr) are overweight or obese and many are unable or unwilling to exercise due to exercise intolerance and/or dyspnea on exertion (DOE). We have identified numerous obesity- related effects that could influence exercise tolerance and DOE in obese adults. We have also identified many age-related ventilatory constraints in nonobese older adults. However, it is unclear whether obesity- related and aging-related effects combine to reduce exercise tolerance, provoke DOE, or contribute to respiratory symptoms in older obese adults. We propose that many of the obesity-related effects in older obese adults are the result of low lung volume breathing, i.e., a reduction in functional residual capacity (FRC) at rest and end-expiratory lung volume (EELV) during exercise. Increased fat on the chest wall produces low FRC and EELV levels, where breathing limitations like expiratory flow limitation (EFL) and enhanced perception of dyspnea are more likely to occur due to the age-related decline in maximal expiratory flow at low lung volumes. Our overall hypothesis is that respiratory limitations, exercise intolerance, DOE, and respiratory symptoms in older obese adults are due to mechanical loading of the thorax and low lung volume breathing. We propose to test this hypothesis with the use an external cuirass (i.e., a plastic shell over the thorax) to mechanically unload the chest wall. This will decrease the load on the thorax thereby increasing FRC at rest and EELV during exercise, and potentially decrease the work of breathing during exercise. The overall objective of this application is to investigate the effects of obesity on lung function, exercise tolerance, and DOE in older obese adults as compared with older adults without obesity, using a novel probe for mechanically unloading the thorax at rest and during exercise. We will use 1) continuous negative cuirass pressure, and 2) assisted biphasic cuirass ventilation to decrease obesity-related effects in older obese adults. Our approach will be to examine respiratory function, exercise tolerance, and DOE with and without mechanical unloading in older obese men and women (65-75 yr), including those with respiratory symptoms, as compared with older adults without obesity. Specific Aims: We will test the following hypotheses: Aim 1) Obesity will decrease respiratory function but to a greater extent in older obese adults with respiratory symptoms; Aim 2) Obesity will decrease exercise tolerance but not cardiorespiratory fitness, except in older obese adults with respiratory symptoms where both may be reduced; Aim 3) Obesity will increase DOE but to a greater extent in older obese adults with respiratory symptoms; and Aim 4) Mechanical unloading of the thorax will improve respiratory function, exercise tolerance, and DOE in older obese adults, but to a greater extent in older obese adults with respiratory symptoms. These results will have broad and immediate clinical impact on the care of older obese adults with DOE.