Describe the effects of ageing on the respiratory system.

5% of candidates passed this question.

Answers should have included the effects of ageing on the efficiency of gas exchange, how the expected PaO2 changes with age, and its causation. Anatomical changes should have been included as should changes in lung volumes, particularly the significance of an increased closing volume. Marks were not awarded for the effects of disease states.


  • Ageing is the accumulation of irreversible molecular and cellular damage over time
  • Respiratory System maximal function is reached at age 20 (F) and 25 (M)
  • Throughout the remainder of life, ageing is associated with a progressive decline in respiratory performance



Effect on Compliance/Resistance

Rib cage calcification and osteoporotic changes in the shape of the thorax

↓CW Compliance

Imbalance of crosslinking in elastic fibre network → static elastic recoil pressure declines

Loss of elastic recoil of lung parenchyma (increased distensibility)

Peripheral airway closure contributes minimally to total RAW and when adjusted for lung volume changes

RAW stable

Lung Volumes/PFTs


Effect on Lung Volumes/PFTs

↓supporting tissue of small airways → premature airway closure

­↑Closing Volume

↓bronchiole diameter

↓Expiratory Flow

↓elastic recoil → lungs more distensible

­↑Residual Volume

­↑CW elastic recoil + ↓elastic recoil of lung parenchyma (ie breathing at higher lung volumes)


↓elastic recoil counterbalanced by increased elastic load of CW

TLC not much change

↓CW Compliance + Increased Lung distensibility (reduced elastic recoil parenchyma)



↓Peak Flow

Reduction of maximal inspiratory flow will determine bronchodilator use; lung deposition will not be achieved if high insp flow rates required



Effect on WoB

Osteoporosis & Vertebral fractures → Increased AP diameter & Kyphosis → modify curvature & compliance of Diaphragm

↓ability to generate force = Increased WoB

Increased FRC

Elderly breathe at higher lung volumes cf younger subjects → increasing elastic load on CW

­↑WoB during normal tidal breathing

↓nutrition = ↓respiratory muscle strength


Kyphosis + Increase AP diameter = ↓ force generation by diaphragm


Respiratory muscle dysfn

Hypoventilation, SOB, reduced exercise tolerance, resp failure

Gas Exchange


Effect on Gas Exchange

Increase in V/Q units with high ratio (dead space) + low V/Q ratio (shunt/venous admixture)

Large no’s of low V/Q units due to an increase Closing Volume (as CV approaches/= FRC) → premature airway closure

Especially prominent in the peripheral airways due to loss of supporting tissues


­↓A-a difference

Reduction in transfer of CO due to;

increased V/Q heterogeneity, reduced alveolar SA, rection in capillary blood volume


Dilation of alveoli and enlargement of air spaces

↓SA for gas exchange

Control of Ventilation


Effects on Ventilation

MV same at rest

with↑ ­RR and ↓Vt

Reduced ability to receive signals, integrate and generate appropriate output

↓response to hypoxia & hypercapnia