An 80-year-old man has been participating in a longitudinal study of aging. He has no major medical conditions. Arterial blood gas samples are obtained every decade, on room air at sea level, to monitor long-term changes in pulmonary gas exchange. Compared to 30 years ago, which of the following results is most consistent with normal aging?

Question

An 80-year-old man has been participating in a longitudinal study of aging. He has no major medical conditions. Arterial blood gas samples are obtained every decade, on room air at sea level, to monitor long-term changes in pulmonary gas exchange. Compared to 30 years ago, which of the following results is most consistent with normal aging?
An 80-year-old man has been participating in a longitudinal study of aging. He has no major medical conditions. Arterial blood gas samples are obtained every decade, on room air at sea level, to monitor long-term changes in pulmonary gas exchange. Compared to 30 years ago, which of the following results is most consistent with normal aging? A) A B) B C) C D) D E) E

Quizplus · Accepted Answer

11ec160b_3cdb_507e_9249_57caee73157b_MD0001_00 The human respiratory system undergoes significant changes during normal aging. Pulmonary gas exchange becomes subtly impaired due to a sequence of gradual changes: In contrast to decreased PaO₂, the partial pressure of carbon dioxide in arterial blood (PaCO₂) (reflecting total alveolar ventilation) is not significantly changed. Although dead space increases and peak diaphragm strength is reduced, these changes are not enough to cause alveolar hypoventilation by themselves; resting hypoventilation (elevated PaCO₂) at any age is always pathologic. Instead, elderly persons are less able to compensate for high minute ventilation loads (eg, sepsis, thyrotoxicosis), making them prone to hypercapnia when acutely ill. Educational objective: Normal aging is characterized by a gradual increase in ventilation-perfusion mismatch (due to basilar microatelectasis causing shunt effect) and increased dead space (loss of alveolar surface area). This manifests as a wider alveolar-arterial oxygen gradient (ie, decline in PaO₂) without hypoventilation (normal PaCO₂).

An 80-Year-Old Man Has Been Participating in a Longitudinal Study