Aging of the Respiratory System: Impact on Pulmonary Function Tests and Adaptation to Exertion
Section snippets
Structural changes in the respiratory system related to aging
Most of the age-related functional changes in the respiratory system result from three physiologic events: progressive decrease in compliance of the chest wall, in static elastic recoil of the lung (Fig. 1), and in strength of respiratory muscles.
Specifics of pulmonary function testing in an older population
The application of conventional quality control standards to objective assessment of pulmonary function in older subjects may prove difficult because of mood alterations, fatigability, lack of cooperation, or cognitive impairment. Indeed, prevalence of dementia increases with aging, reaching 5.6% after age 75, 22% after age 80, and 30% as of age 90 [50]. The relationship between ability to perform spirometry and cognitive function in the elderly is reported by several investigators [51], [52],
Changes in arterial oxygen tension and ventilation-perfusion relationships
Wagner and coworkers, using the MIGET, report an increase, with aging, in V/Q imbalance, with a rise in units with a high V/Q (wasted ventilation or physiologic dead space) and in units with a low V/Q (shunt or venous admixture) [87], [88]. The decrease in Pao2 with age is described a consequence of this increased heterogeneity of V/Q and, in particular, of the increase in units with a low V/Q (dependent parts of the lung, poorly ventilated during tidal breathing, as reflected by an increased
Aging and ventilatory responses
Aging is associated with a marked attenuation in ventilatory responses to hypoxia and hypercapnia [95], [96], [97]. Kronenberg and Drage compared the responses to hypercapnia and hypoxia in eight healthy young men (22–30 years old) with those of eight older men (64–73 years old) [95]. In the older subjects, ventilatory response to hypoxia was four times less than that of the younger group; response to hypercapnia was decreased by 58%. Mouth occlusion pressure (P0.1), an index of respiratory
Performance during the 6-minute walk test
In subjects who do not have significant osteoarticular or neuromuscular limitation, the 6-minute walk test is a widely used standardized measurement for evaluating physical function; results of a 6-minute walk test are useful to quantify physical limitation and monitor progression of disease in chronic obstructive or restrictive disorders, CHF, or pulmonary vascular diseases; performance is correlated with health-related quality-of-life scores and predictive of morbidity and mortality in
Summary
Compliance of the chest wall and the respiratory system and lung elastic recoil decrease with aging, resulting in static air trapping (increased RV), increased FRC, and increased work of breathing. Respiratory muscle function also is affected by aging, either as a consequence of geometric changes in the rib cage, nutritional status (lean body mass, body weight), cardiac function, or through the age-related reduction in peripheral muscle mass and function, referred to as sarcopenia. In subjects
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