Gas Exchange and Control of Breathing in Elderly and End-of-Life Diseases
Aging is characterized by a progressive decline in physiological capacity, with alterations of lung structure and reduction in pulmonary function, respiratory muscle strength, and gas exchange with decline of the arterial oxygen tension (PaO2) and diffusion capacity of the lungs for carbon monoxide (DLCO). The decline in oxygen diffusion capacity does not affect the capacity to maintain an adequate gas exchange and should be distinguished by the pathological features of lung disease. On the other hand, the CO2 elimination is guaranteed by the increased ventilation and the arterial carbon dioxide tension (PaCO2) remains constant. All these changes determine an increase vulnerability in case of pathological conditions when the physiological demand increases above the reduced capacity as well as in the palliative context.