[Hypoxemia and aging (author's transl)]

Hypoxemia during rest reveals the aging of the respiratory tract. The evolution curve of the PaO2 related to age is parallel to that of static elastic recoil pressure. This hypoxemia is moderate and without any serious functional consequences in a healthy subject. Abnormalities of the ventilation-perfusion ratio are the main causes. The increase of the anatomical dead space and the increase of the right-left shunt only play a moderate part. On the other hand the increase of closing volume seems the major factor. Thus the ventilation distribution becomes dependent on the amplitude of the tidal volume. The response of the aged subject to hypoxia is lessened for mechanical and neurological reasons explaining why a respiratory distress can appear rapidely and sometimes unexpectedly.