respiratory system

Question 1

age changes in aiways

Answer 1

large airways- diameter is unchanged, increased calcification
small ariways- number declines, increased tendancy to collapse- increased closing of basal airways with age, contributes to increased residual volume

Question 2

alveolar changes

Answer 2

increased diameter of alveoli and alveolar ducts with age
- possibly due to disruption of collagen fibres- comprise 15-20% of lung weight
- proportion of air in alveoli declines
- increased alveolar dead space- ventilated but not adequately perfused

reduced SA with age
- causes reduced surface tension
- reduced diffusion capacity

Question 3

pulmonary ventilation

Answer 3

compliance- indicator of expandability
low complicance requires greater froce
high compliance requires less force

as volume increase - pressure inside falls so air flows in
as volume decreases- pressure inside rises so air flows out

Question 4

factors affecting compliance

Answer 4

connective tissue structure of lungs
level of surfactant production
mobility of thoracic cage

Question 5

chest wall vs lung compliance

Answer 5

thoracic cage- chest wall recoil promotes expansion
lungs- elastic recoil promotes contraction, opposed by surface tension
functional residual capacity- capacity at resting position ie with muscles relaxed, chest wall and lung recoil balanced

Question 6

chest wall changes with age

Answer 6

thoracic shape- loss of vertebral height and muscular changes contribute to kyphosis, increased anteroposterior depth

calcification of costal cartilage- reduced chest wall compliance, contributes to increased functional residual volume
would be expected to reduce vital capacity but is counteracted by reduced elastic recoil that increases total lung capcity

Question 7

respiratory muscle ageing

Answer 7

diaphragm strength is 25% lower in 70s than 20s
diaphragm is more important for changing volume because of increased chest wall stiffness

intercostal muscle mass and strength declines from age 50: deterioration of neuromuscular junctions, reduction of expiratory strength and outward chest wall less opposed so RV increases and vital capacity decreases

reduction of inspiratory strength- would reduce TLC but is offset by reduced lung recoil

Question 8

lung volume capacities with age

Answer 8

TLC maintained as decreased muscle strength is offset by decreased lung recoil
increased FRC from decreased chest wall compliance and decreased lung recoil
increased RV from decreased lung recoil and airway closure

Question 9

closing volume

Answer 9

volume at which small airwats at base begin to close during forced expiration
-airway closure greater during shallow breathing when supine
- airways more expanded at apex than base
- effects of age- CV~10% of total lung capacity and ~30% in older peiple
- effects of disease- if CV exceeds FRC airwats remain closed and alveoli may be underventilated and hypoxic

Question 10

dynamic volume

Answer 10

FEV1 declines may accelerate to 35m/s year
VC declines later by around 25%
shows influence of lung growth and accelerated decline on FEV1

Question 11

gas exchange

Answer 11

changes with age
ventilation/perfusion ratio
- more mismatch in older lung
- more alveolar dead space- inadequately perfused
- airway closure leaves lower lung regions inadequately ventilatied

gas exchange
- arterial po2 can decrease from 95 in 20s to ~75mmhg in 70s
- contributory factors- ventilatory perfusion, reduced Q and lung perfusion

Question 12

control of ventilation with age

Answer 12

reduced sensitivity to chages in arterial po2
at rest, tidal volume is lower and alveolar ventilation is maintained by more rapid breathing
during exercise, greater response to co2 and higher VE/VCO2

Question 13

immune function changes with age

Answer 13

increased risk of infection + illness due to
- Reduced cough reflex
- Reduced ciliary clearance of mucous- reduced beating of cilia, reduced secretion
- Increased concentration of neutrophils- secrete enzymes eg collagenases, elastases, matrix metalloproteinases to allow passage through connective tissue
- Increased inflammatory cytokines- low grade inflammation

Question 14

factors related to age associated decline in lung function

Answer 14

• Tobacco smoking
• Asthma
• Bronchial hyper-responsiveness
• Atopy or increased IgE
• Occupational hazards
• Heavy alcohol consumption
• Obesity
• From cross-sectional studies:
• Respiratory infection in infancy
• Nutritional status at birth
• Maternal or passive smoking
• Poorly controlled childhood asthma

Question 15

respiratory diseases associated with ageing

Answer 15

• Emphysema
• Barrel chest, dyspnoea (shortage of breath), destruction of alveolar walls
• Chronic bronchitis
• Cough with sputum for at least 3 months in two consecutive years
• Cyanotic and hypercapnic (low O2 and high CO 2 )
• Chronic Obstructive Pulmonary Disease (COPD)
• Emphysema and/or chronic bronchitis
• Symptoms: dyspnoea and chronic wheezing and coughing
• Higher incidence/severity of infectious disease e.g. pneumonia, Covid-19

Question 16

implications of age related change in lung function

Answer 16

Physical function
- Although lung function declines with age, CV and muscular change make a larger contribution to reduction in aerobic capacity
- Extremely low lung function will limit exervise capacity and is associated with increased mortality
Susceptibility to infection increased due to:
- Reduced cough reflex, mucous clearance and muscle strength
- Increased susceptibility to airway closure