A 70-year-old woman has been enrolled in a longitudinal research study on aging for the last 30 years. Medical history is significant for osteoporosis; she has developed moderate kyphosis due to gradual loss of vertebral body height. She is otherwise active and healthy with no additional medical issues. She has never smoked. Compared to her physiology testing done years ago, which of the following changes is most consistent with normal aging?

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11ec160b_3cdb_7790_9249_0f203e749d5e_MD0001_00 The human respiratory system undergoes significant changes during normal aging. The mechanics of breathing are compromised due to alteration of lung, chest wall, and total respiratory system compliance: As these mechanical changes occur, there is also a marked increase in dead space ventilation. Although anatomic dead space (nasopharynx to terminal bronchioles) remains constant after early adulthood when the bronchial tree reaches full maturity, alveolar dead space increases with age due to progressive elastin degeneration, alveolar simplification, and capillary dropout. The net result is a mechanically disadvantaged respiratory system (lower compliance) that must contend with increased dead space. A greater work of breathing is required to maintain the same alveolar minute ventilation and the efficiency of breathing (ventilation per unit of work) steadily declines. Educational objective: Normal aging is characterized by decreased respiratory system compliance (increased lung compliance outweighed by higher chest wall stiffness) and increased dead space (loss of alveolar surface area). For this reason, elderly persons are less equipped to tolerate illnesses that impair respiratory compliance and/or gas exchange (eg, pneumonia, pulmonary edema).

A 70-Year-Old Woman Has Been Enrolled in a Longitudinal Research