Aging and respiratory system response for a given CO2 production is higher in older adults rate of decline after age 70 years. There is an increase in compared with younger individuals, suggesting a possible airspace size with aging resulting from loss of supporting increase in dead space ventilation (Vd/Vt) (Table 5). Tenney tissue. Respiratory muscle strength decreases with age and and Miller (1956) studied 18 healthy males between the much more so in men than in women (Table 6). Despite ages of 68 and 89 years and showed that Vd/Vt is a these changes the respiratory system is capable of disproportionately large fraction of total minute ventilation maintaining adequate oxygenation and ventilation during in older individuals (235±67.5 ml). Dead space ventilation the entire life span. However, the respiratory system reserve increases by 55% compared with that of younger adults is limited with age, and diminished ventilatory response to (average Vd/Vt in younger adults 150 ml). A 5 mm Hg hypoxia and hypercapnia makes it more vulnerable to increase in A-a gradient raises dead space ventilation by ventilatory failure during high demand states (ie, heart about 40 ml. Increase in Vd/Vt with age reflects disparity failure, pneumonia, etc) and possible poor outcomes. in the distribution of ventilation and perfusion with age. Moreover, the reduced perception of bronchial constriction Additional age-related changes including reduced heart rate may result in delayed medical attention. Sustained response, cardiac output, and peripheral muscle mass may inflammation of the lower respiratory tract may predispose account for the decline in VO2 max with age rather than reduced lung function alone. Summary There is marked variation in the effect of aging on lung function. Aging is associated with reduction in chest wall compliance and increased air trapping. The decline in FEV1 with age likely has a nonlinear phase with acceleration in Table 6 Anatomical and physiological changes of respiratory system with aging Anatomical Air space size Compliance Chest wall compliance Lung compliance Total respiratory system compliance Muscle strength Maximal inspiratory pressure (MIP) Trans diaphragmatic pressure (Pdi) Maximum voluntary ventilation (MVV) Lung function FEV1 FVC TLC Vital capacity Functional residual capacity Residual Volume DLCO/VA Exercise capacity VO2 max Dead space ventilation Immunology Bronchial fluid Neutrophils % Ratio of CD4+/CD8+ cells Epithelial lining fluid antioxidants Increased Decreased Increased to unchanged Decreased Decreased Decreased Decreased Decreased Decreased Unchanged Decreased Increased Increased Decreased Decreased Increased Increased Increased Decreased Abbreviations: DLCO, diffusing capacity of carbon monoxide; FEV1, forced expiratory volume in one second; FVC, forced vital capacity;TLC, total lung capacity;VO2, oxygen consumption;VA, alveolar volume. Clinical Interventions in Aging 2006:1(3) older adults to increased susceptibility to toxic environmental exposure and accelerated lung function decline. As Americans are getting older, future studies need to address the clinical implication of “normal” age-related changes of the respiratory system. References Abrass IB, Scarface PJ. 1982. Catalytic unit of adenylate cyclase: reduced activity in aged-human lymphocytes. J Clin Endocr Metab, 55:1026-8. Burrows B, Lebowitz MD, Camilli AE, et al. 1986. Longitudinal changes in forced expiratory volume in one second in adults. Am Rev Respir Dis, 133:974-80. Connolly MJ. 1993. Aging, late-onset asthma and the beta-adrenoceptor. Pharm Therapeutics, 60:389-404. Connolly MJ, Crowley JJ, Charan NB, et al. 1995. Impaired bronchodilator response to albuterol in healthy elderly men and women. Chest, 108:401-6. Crapo RO, Morris AH, Gardner RM. 1981. Reference spirometric values using techniques and equipment that meets ATS recommendations. Am Rev Respir Dis, 123:659-64. Creticos P, Knobil K, Edwards LD, et al. 2002. Loss of response to treatment with leukotriene receptor antagonists but not inhale corticosteroids in patients over 50 years of age. Ann Allergy Asthma Immunol, 88:401-9. Cuttitta G, Cibella F, Bellia V, et al. 200l. Changes in FVC during methacholine-induced bronchoconstriction in elderly patients with asthma: bronchial hyper responsiveness and aging. Chest, 119:1685- 90. Dockery DW, Ware JH, Ferris BG, et al. 1985. Distribution of forced expiratory volume in one second and forced vital capacity in healthy, white, adult, never smokers in six U.S. cities. Am Rev Respir Dis, 131:511-20. Enright, PL, Kronmal RA, Higgens M, et al. 1993. Spirometry reference values for women and men 65 to 85 years of age. Cardiovascular Health Study. Am Rev Respir Dis, 147:125-33. Enright PL, Kronmal RA, Manolio TA, et al. 1994. Respiratory muscle strength in the elderly. Am J Respir Crit Care Med, 149:430-8. Feldman RD, Limbird LE, Nadeau J, et al. 1984. Alterations in leukocyte β-adrenergic affinity with aging. A potential explanation of altered β-adrenergic sensitivity in the elderly. N Engl J Med, 310:815-19. Gillooly M, Lamb D. 1993. Airspace size in lungs of lifelong non-smokers: effect of age and sex. Thorax, 48:39-43. Hopp RJ, Bewtra A, Nair NM, et al. 1985. The effect of age on methacholine response. J Allergy Clin Immunol, 76:609-13. 259