Lung Volumes, Respiratory Mechanics Flashcards by Jack Cuthbertson

Branching of airways
1
2
3
4

1) Primary bronchus
2) Secondary bronchus
3) Bronchiole
4) Alveoli

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Divisions of airways

Conducting system

Exchange surface

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Conducting system

Trachaea, primary, secondary bronchi

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Number of divisions of airways

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Alveolar division

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Bronchiolar divisions

12-23

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Diameter of trachaea

15-22mm

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Diameter of alveoli

0.3mm

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Number of alveoli

3 - 6 x 10^8

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Cross-sectional area of trachaea

2.5cm^2

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Cross-sectional area of alveoli

10^6

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Structure of trachaea and larger bronchi
1
2

1) Fairly rigid, non-muscular tubes

2) Rings of cartilage prevent collapse

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Structure of bronchioles
1
2
3

1) No cartilage to hold them open
2) Smooth muscle in walls innervated by autonomic nervous system
3) Sensitive to some hormones, chemicals

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Factors that affect airway resistance
1
2
3
4
5
6

1) Length of airways (constant)
2) Viscosity of air (normally constant)
3) Diameter of airways
4) Physical obstruction
5) Bronchioconstriction
6) Bronchiodilation

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What causes bronchioconstriction?
1
2
3

1) Parasympathetic nervous system
2) Histamine
3) Leukotrienes

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What causes bronchiodilation?

1) Carbon dioxide

2) Epinephrine (beta2 adrenoceptors)

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Difference between lung compliance and elasticity

Compliance - Ability of lungs to stretch

Elasticity - Ability of lungs to spring back after being stretched

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Disease that reduces lung compliance

Pulmonary fibrosis

Inelastic scar tissue is formed

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Disease that reduces lung elasticity

Emphysema

Elastin tissues in lungs are destroyed

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Natural inclination of ribs

Expand

This would happen without intercostal muscles

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Natural inclination of lungs

Collapse

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Boyle’s law

P1V1 = P2V2

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Natural inclination of alveoli

Collapse

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Why do alveoli naturally want to collapse?

Surface tension of water lining them

Water more attracted to other water molecules than gasses

Liquid-liquid attraction opposes any force that seeks to increase it’s size

Liquid-liquid attraction also seeks to reduce volume of alveolus

Law of LaPlace

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Law of LaPLace

Pressure in a sphere = 2xSurface tension/Radius

Implication of law of LaPlace

Smaller spheres have higher internal pressure (if surface tension is constant) Therefore small alveoli resist inflation

Mechanisms that oppose alveolar collapse 1 2

1) Surfactant | 2) Alveolar interdependence

Surfactants 1 2 3

1) SURFace ACTive AgenTS 2) Disrupt attractive forces between water molecules 3) Replace water molecules at alveolar surface

Effect of surfactant 1 2 3

Decrease surface tension Decrease Intraalveolar pressure Decrease resistance of lung to stretch

Alveolar interdependence

Walls of alveoli joined to walls of other alveoli | If one alveolus tries to collapse, attached walls of other alveoli recoil, pull it back into shape

Which cells secrete surfactant?

Type II alveolar cells

Where is surfactant most concentrated?

In smaller alveoli

Types of respiratory diseases

Obstructive lung disease | Restrictive lung disease

Obstructive lung disease

Narrowing of lower airways Increase resistance of lower airways More difficult to expire EG: Asthma, emphysema, chronic bronchitis

Restrictive lung disease

Reduction in lung compliance More difficult to inflate lung EG: Pulmonary fibrosis

Spirometry

Measurement of lung volumes

The four lung volumes

1) Residual volume 2) Expiratory reserve volume 3) Tidal volume 4) Inspiratory reserve volume ((DEAD SPACE))

Boundaries of normal inspiration and expiration

Tidal volume

Normal tidal volume

500mL

Normal inspiratory reserve

3000mL

Normal expiratory reserve

1100mL

Normal residual volume

1200mL

Normal lung capacity

5800mL

Vital capacity

Expiratory reserve + tidal volume + inspiratory reserve Total lung volume - residual volume

Normal vital capacity

4600mL

Functional residual capacity

Expiratory reserve volume + Residual volume

Inspiratory capacity

Inspiratory reserve + Tidal volume

What is capacity?

When a larger volume than normal of air enters the lungs

Can residual volume be expirated?

What does residual volume do?

Keeps lungs inflated | Very hard to inflate completely deflated lungs

FEV1

Forced expiratory volume in 1 second

Normal FVC/FEV1 ratio

80%

FVC

Forced vital capacity Volume of air that can be expired after full inspiration Normally ~4600mL

How much of lung capacity can normally be expirated in 1 second?

80%

Normal forced vital capacity

Normal forced expiratory volume in 1 second

What does forced vital capacity do in obstructive lung disease?

Decrease markedly

What does the FEV1/FVC ratio do in restrictive lung disease?

Increase a lot FVC decreases markedly

What isn't changed with obstructive lung disease?

Total lung capacity | Residual volume increases

What does the FEV1/FVC ratio do in obstructive lung disease?

Decrease FVC decreases, but FEV1 decreases even more

What doesn't decrease with constrictive lung disease?

FEV1/FVC ratio can increase or stay the same | Residual volume stays the same

What increases with obstructive lung disease?

Residual volume (as less air can leave lungs)

Anatomical dead space

Parts of airways where gas exchange doesn't occur EG: Trachaea, bronchi

Amount of first exhaled air that is from dead space

150mL

Where is dead space air located? 1) 2)

1) 150 mL of fresh dead space air is in trachaea and bronchi from most recent breath 2) The first 150mL of air into the alveoli is stale air from dead space

pO2 of fresh dead space air

150mmHg

pO2 of stale dead space air

100mmHg

Minute ventilation

What is minute ventilation?

Total ventilation over a fixed time period (often a minute) | Ve = Tidal volume x Frequency of ventilation

Average number of breaths per minute

Average Ve

6L/min

Alveolar ventilation

What is alveolar ventilation?

Volume of alveolar air - physiological dead space per unit time

What is the most efficient way to increase Va?

Increase tidal volume Increasing frequency increases the impact that physiological dead space has on Va

Normal Va

4.2L/min

Eupnea

Normal breathing

Hyperpnea

Increased respiratory rate or volume Responding to increased metabolism

Hyperventilation

Increased respiratory rate or volume Without increased metabolism

Hypoventilation

Decreased alveolar ventilation

Tachypnea

Increased breathing rate, decreased depth

Dyspnea

Air hunger

Apnea

Cessation of breathing

Lung Volumes, Respiratory Mechanics Flashcards

(82 cards)