Expansion
Loss of elastic recoil, stiffer chest wall, rising closing capacity and falling oxygen tension
Expansion
Lungs
- Loss of elastic recoil, sometimes called senile emphysema, though without alveolar wall destruction
- Residual volume and functional residual capacity rise
- Vital capacity falls; total lung capacity is roughly unchanged
- Closing capacity rises, exceeding functional residual capacity from about 44 years supine and 66 years erect
- Diffusing capacity falls
Chest wall
- Stiffer, from costal cartilage calcification and kyphosis, so compliance falls
- Respiratory muscle strength declines
Control
- Blunted ventilatory response to hypoxia and hypercapnia
- Impaired cough and mucociliary clearance
The net effect is a fall in arterial oxygen tension of roughly 0.4 kPa per decade after young adulthood, and a marked reduction in reserve. Older patients therefore tolerate pneumonia, anaesthesia and abdominal surgery poorly, and are prone to postoperative atelectasis and hypoxaemia.