Pulmonary System

1
Pulmonary System

• Aging effect on system primarily seen during
  maximal exercise
• A given external effort, older person has higher
  respiratory work rate

2
Pulmonary System Structure

• Major age-related change
• Reduced elastic recoil of lung
• Stiffening of the chest wall
• Lung Connective tissue consists of
• Elastin, collagen, proteoglycans cross-linked
  to provide lung with elastic recoil
• Total elastin and collagen remain unaltered with
  age
• Surfactant effect on recoil is unchanged
• Lessens surface tension lowers resistance to
  expansion (inspiration
• Prevents collapse of alveoli on expiration

3
Pulmonary System Structure

• Generally proposed
• Elastic recoil of lung is reduced by changes in
  spatial arrangement of cross-linking of elastin
  and collagen fibers
• Alveolar-capillary surface area
• 70 m2 age 20y 60 m2 age 70-80y
• ?Stiffening of chest wall costal cartilage
  calcification ? in rib to vertebral
  articulations narrowed intervertebral discs
  change in chest shape
• Calcification and reduced compliance of the
  pulmonary arteries occurs consistently with aging
  

4
Pulmonary System Structure

• Age associated changes in respiratory muscle
  structure found in animals
• Aging diaphragm has tendency to reduce muscle
  mass through reduction of Type II fibers
• Changes are highly variable

5
Translation of Structural Changes to Pulmonary
Function - Rest

• ? limitation to expiratory flow
• Positive pressure outside airway exceeds inside
  pressure (created by reduced elastic recoil)
• Concave scooping shown in maximum Flowvolume
  loop
• FEV1.0? declines in parallel with expiratory flow
  limitation
• Partially due to increased chest stiffness
• Increased airway closure at low lung volumes
• Both above increase during 20s, plateau until
  late 30s, then the gradual decline

6
Translation of Structural Changes to Pulmonary
Function - Rest

• Age-dependent small airway closure increases
  airway resistance at low lung volumes ? leading
  to ?residual lung volume w/aging
• ? closing capacity in older adult lung volume
  at which small airways close at terminal
  bronchiole level
• Sixth decade closing capacity functional
  residual volume ? maldistribution of inspired air
  impaired gas exchange

7
Pulmonary System and AgingAnatomical Changes

• Bronchial tree
• Reduction in mucous glands
• Reduction in cilia
• Loss of cartilage support
• Increased airway resistance
• Lung Tissue
• Decreased radial elastic fibres in small airways
• Thicker alveoli
• Implications
• Increased risk of infection, airway collapse,
  work of breathing

8
Pulmonary Volumes and Capacities
9
Pulmonary System Regulation during Acute Exercise
Young, Untrained Adult

• Airways, lung and muscular chest wall are
  over-built with respect to functional demands
• Ventilation gas exchange imposed by exercise
• Key Responses
• 1. Alveolar ventilation increases in near
  exact proportion to increasing CO2 production
• 2. During heavy exercise (gt65 VO2max) alveolar
  ventilation increases out of proportion to CO2
  production
• 3. Ventilation increased by ?breathing frequency
  and ? VT
• 4. Limits of the maximum expiratory flowvolume
  loop are not reached

10
Pulmonary System Regulation during Acute Exercise
Young, Untrained Adult

• 5. Oxygen cost of breathing increases out of
  proportion to increased ventilation during
  strenuous exercise
• 6. Pulmonary vascular resistance ? during
  exercise as pulmonary arterial pressure increases
  slightly 2x
• 7. Structures of the terminal gas exchange unit
  and pulmonary vasculature are perfectly able to
  accept increase in Q during exercise

11
Pulmonary System Regulation during Acute Exercise
Aging Effects

• Subjects Age (61-79yrs) mean69 VO2max 44? 2
  ml/kg/min, range 25-62 ml/kg/min
• 1. Expiratory flow limitation occurs at lower
  exercise intensities
• At Vemax, 25-35 of the VT will be flow limited
  at a Vemax of 70-80 l/min in normally fit 70 yr
  old
• Up to 50 VT may be flow limited at a Ve of
  110-120 l/min in highly fit (VO2max) 40-45
  ml/kg/min

12
Pulmonary System Regulation during Acute Exercise
Aging Effects

• 2. End-expiratory lung volume (EELV) older
  subject shows a gradual increase in EELV back
  toward resting level
• Must rely on hyperinflation to increase
  ventilation
• 3. A greater dead space ventilation w/aging
  thus requiring an increased ventilatory response
  to maintain PaCO2 and normal Va
• Variable reduction in VT occurs in parallel with
  reduction in vital capacity
• Maldistribution of air contribute to increased
  VD/ VT

13
Pulmonary System Regulation during Acute Exercise
Aging Effects

• 4. Increase in work of breathing during exercise
• Overall ventilatory response requires increased
  pleural pressure
• Increased expiratory flow resistance
• Thus increasing respiratory muscle VO2 (10-12)
  of total body VO2 for untrained 70-y-old at Ve
  (75-80 L/min)
• VO2RM-may exceed 15 of total VO2max in highly
  trained 70-y-old at a Ve (110 L/min)

14
Pulmonary System Regulation during Acute Exercise
Aging Effects

• Pulmonary hemodynamics during exercise are
  altered because of the reduction in pulmonary
  arteriolar compliance with healthy aging
• Pulmonary artery pressure is increased at any
  given exercise cardiac output or VO2 (Reeves,
  1989)
• Evidence suggests that intense exercise may
  induce pulmonary edema leading to a diffusion
  limitation and maldistribution of air

15
Aging Effects on Pulmonary Function and Exercise

• Variable Test 1 Test 2
  Change
• TLC, L 6.70 6.55
  -1.6
• VC, L 4.16
  3.72 -10.6
• RV, L 2.39
  2.68 -13.2
• FRC, L 3.82 4.03
  -5.2
• FEV1.0 , L 3.18 2.78
  -12.8
• MVV, L. min-1 127.2 111.1
  -12.6

16
Subject Characteristics (McCarron et al., 1995

• Variable Test 1 Test 2
• Age, yr 67.0 72.9
• Ht, cm 171.6 171.2
• Wt, kg 65.2
  65.5
• VO2max ml/kg/min 45.3 40.3
• VO2max pred 201.4 201.0
• Walk/run, 28.0 23.5
• mi/wk

17
Lung Function at rest Influence of age and
fitness
18
Cross-sectional vs. Longitudinal Data

• Rate of decline in FEV1.0 increased 60 in cross
  sectional vs. 350 in longitudinal at age 45
  versus 25 y
• Two critical decades
• Women demonstrated similar trends
• Confounding variables such as smoking history

19
Pulmonary Adaptations to Chronic Exercise

• Maximum flow rates (FEV1.0 or MEF50) are 20-30
  greater in the fit.
• Not known if physical training reduces the normal
  aging effect on lung elastic recoil and resting
  pulmonary function

20

• Spirometry is a forced vital
• capacity maneuver displayed
• graphically as volume vs. time
• or flow vs. volume.

21

• Tidal volume (TV) is the volume
• of air entering or leaving the
• nose or mouth per breath.

22

• Inspiratory Reserve Volume (IRV)
• is the volume of gas that is inhaled
• into the lungs during a maximal
• forced inspiration starting at the
• end of a normal tidal inspiration.

23

• Vital Capacity (VC) is the volume
• of air expired after a maximal
• inspiration to total lung capacity.
• Forced Vital Capacity (FVC) is a
• maximal expiratory effort during
• this maneuver.

24

• Residual Volume (RV) - is the volume of gas left
  in the lungs after a maximal forced expiration.

25

• Functional Residual Capacity (FRC)
• is the volume of gas remaining in
• the lungs at the end of a normal
• tidal expiration.
• FRC ERV RV

26
Forced Expiratory Volume (FEV)

• FEV1.0 is the volume of gas exhaled in 1 sec by
  a forced expiration from full inspiration
• Forced Vital Capacity (FVC) is the forced total
  volume of gas exhaled after a full inspiration
• FEV1.0 / FVC is normally 80

27
Maximum Voluntary Ventilation (MVV)

• MVV is the maximum volume of air
• that can be breathed in 1 min.

28

• Older persons elicit similar relative ()
• increase in VO2max as young adults, but
• absolute increase generally smaller. Also,
• increase in VO2max similar in older
• men and women, but absolute increase
• less in women than men. However, there
• is significant variability in the magnitude
• of the increase in VO2max in older
• persons.