Effects of ageing on the respiratory system

The ageing lung

"Senile emphysema" - the ageing lung looks like emphysema without inflammation or destruction of alveolar walls.

Component	Change with age
Lung parenchyma	dec elastic recoil, inc compliance
Chest wall	dec compliance (rib calcification, kyphosis, disc space loss)
Respiratory muscles	dec strength (MIP/MEP fall ~15-20% by 70)
Alveoli	dec number, inc alveolar duct size, dec surface-to-volume ratio
Control of breathing	Blunted response to hypoxia and hypercapnia
Immunity/mucociliary	dec clearance, immunosenescence

Total lung capacity is essentially unchanged - the opposing changes in lung and chest wall compliance cancel out
The functional consequence is loss of reserve, not resting impairment - which is why it only becomes visible under stress

FEV1 declines ~25-30 mL/yr after age 35, accelerating to ~40-60 mL/yr after 65
FVC falls similarly; FEV1/FVC ratio falls ~0.2%/yr
- -> a fixed FEV1/FVC cutoff of 0.70 over-diagnoses COPD in the elderly -> use the lower limit of normal (LLN, z-score < -1.645)
PaO2 falls with age (~0.3 mmHg/yr); a rough guide: expected PaO2 ~100 - (0.3 x age). PaCO2 does not change
VO2max falls ~8-10% per decade
>65s account for the majority of pneumonia, COPD and respiratory failure admissions and deaths

Structural

dec elastic fibres and inc type III collagen -> dec elastic recoil -> inc static compliance
- -> premature small airway closure during expiration (small airways have no cartilage and rely on parenchymal tethering for patency)
dec alveolar number, inc alveolar duct diameter, dec alveolar surface-to-volume ratio
- -> dec DLCO ~0.2-0.3 mL/min/mmHg per year
Chest wall: costal cartilage calcification, kyphosis, osteoporotic vertebral fractures -> dec chest wall compliance, inc work of breathing
Diaphragm flattening (from inc FRC) -> mechanical disadvantage
Sarcopenia of respiratory muscles

	Change
TLC	Unchanged
RV	inc (air trapping from early airway closure)
FRC	inc
VC	dec
RV/TLC	inc (from ~25% at 20 to ~40% at 70)
Closing volume	inc - encroaches on tidal volume by ~65 supine, ~45 standing

inc closing volume -> dependent airway closure during tidal breathing -> V/Q mismatch -> inc A-a gradient -> dec PaO2
This is V/Q mismatch, not shunt - it corrects with supplemental oxygen

Blunted ventilatory response to both hypoxia and hypercapnia (~50% reduction)
- -> the elderly do not look distressed when hypoxic or hypercapnic
- -> tachypnoea may be absent in severe pneumonia
The decline in maximal heart rate is the single largest contributor to the age-related fall in VO2max (Fick: VO2max = SV x HR x a-vO2 difference)
- Ventilation is still not the limiting factor in the healthy elderly - the breathing reserve is preserved

dec mucociliary clearance, dec cough strength and reflex, dec IgA
dec swallow coordination -> silent aspiration
Immunosenescence + inflammaging -> poorer vaccine responses, higher infection severity

Use LLN/z-scores, not fixed ratios - GLI 2012 (and GLI Global 2022 race-neutral) reference equations
- FEV1/FVC <0.70 in an 80-year-old is frequently normal
Correct DLCO for haemoglobin and alveolar volume
Expect reduced MIP/MEP; interpret against age-specific norms
A normal respiratory rate and absent tachypnoea do not exclude respiratory failure
Spirometry quality falls with cognitive impairment and weakness - check the flow-volume loops before calling a result abnormal

	Ageing	COPD
Airflow obstruction	Within LLN	Below LLN
Symptoms	Reserve loss only	Dyspnoea, cough, sputum, exacerbations
CT	Mild uniform enlargement of airspaces	Destruction, bullae, bronchial wall thickening
Response to bronchodilator	Nil	Variable
Inflammation	Absent	Present

A breathless 80-year-old has a disease until proven otherwise. "It is just their age" is a diagnosis of exclusion made far too often.

Do not attribute breathlessness to age - investigate for anaemia, heart failure, deconditioning, ILD, COPD, PE, cancer, thyroid disease
Vaccination
- Annual influenza; adjuvanted/high-dose formulations preferred >=65
- Pneumococcal per the Australian Immunisation Handbook (13vPCV then 23vPPV schedule; earlier and additional doses for Aboriginal and Torres Strait Islander people and those with risk conditions)
- COVID-19 boosters; RSV vaccination >=60-75 years; herpes zoster
Exercise training and pulmonary rehabilitation work at any age - the fall in VO2max is substantially reversible
Optimise nutrition and treat sarcopenia; inspiratory muscle training where indicated
Osteoporosis treatment - vertebral fractures directly reduce vital capacity
Smoking cessation - benefit at any age
Assess swallowing after stroke, in Parkinson disease and in dementia; upright positioning, oral care
Peri-operatively: chest physiotherapy, early mobilisation, adequate analgesia (avoid over-sedation - the blunted CO2 response means opioids are less well tolerated)
Careful oxygen prescription in those with chronic hypercapnia - target SpO2 88-92%

COPD, ILD, lung cancer (age is the dominant risk factor for all three)
Aspiration pneumonia, community-acquired pneumonia
Obstructive sleep apnoea and central apnoea - prevalence rises with age
Heart failure with preserved ejection fraction
Sarcopenia, frailty, osteoporosis, kyphosis
Immunosenescence - reduced vaccine efficacy
Anaesthetic and opioid sensitivity; postoperative pulmonary complications
Polypharmacy - sedatives, opioids, beta-blockers, amiodarone (pneumonitis), methotrexate, nitrofurantoin

Age-related change is gradual, symmetrical and non-inflammatory, and by itself rarely causes symptoms at rest
The clinical consequence is loss of reserve
- -> an illness that a 30-year-old compensates for precipitates respiratory failure at 80
- -> slower recovery and higher mortality from pneumonia, surgery and exacerbations
Smoking, occupational exposure and recurrent infection accelerate the decline steeply - the trajectory is modifiable
The Fletcher-Peto framing: everyone declines, but the susceptible smoker crosses the disability threshold decades earlier
Exercise capacity is the most reversible component; ventilatory mechanics are not
Blunted chemosensitivity, weak cough and silent aspiration explain most of the atypical presentations of respiratory disease in the elderly

11 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.