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Respiratory Disorders II

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Lecture Outline1- Spirometry: Volume/Time & Flow/Volume Curves

2- Use of Spirometry in Obstructive & Restrictive Lung Diseases

3- Spirometry Live Demonstration

4- Aetiology & Pathological Features of Chronic Bronchitis

5- Aetiology & Pathological Features of Emphysema

6- Effect of Obstructive Lung Disease on Lung Volumes & Capacities

7- Aetiology & Pathological Features of Restrictive Lung Disease

8- Respiratory Function Tests- Diagnostic Significance

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Spirometry in the wards = 2 types - 1-Vol-time - 2- Flow- vol

Spirometry

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Spirometry- Vol/Time

Vol

um

e (L

)

0

1

2

3

4

5

6

Time (s)0 1 2 3 4

FE

V1

Normally,FEV1/FVC ratio= 0.8

or FEV1 = 80% FVC

For

ced

Vit

al C

apac

ity

FV

C

From fully inspired statepatient expels all air in theirlungs as forcefully as possible

25%

75%

Slope of the initial line

gives the flow rateFEF25% -75%

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Forced Expiratory Flow (FEF 25% – 75% )

Measure of expiratory flow rate (V/t) over middle half of the

FVC curve

More conveniently done on Flow-Vol spirometry … Directly read off from the curve

SIG = Early airflow obstruction

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Vol-Time Spirometry in Obstructive Lung DiseaseV

olu

me

(L)

0

1

2

3

4

5

6

Time (s)0 1 2 3 4

Obstructive Lung DiseaseTotal Volume (TLC and

FVC) may be normalbut FEV1 is reduced

And FEV1/FVC ratio <0.8(<50% here)

For

ced

Vit

al C

apac

ity

FE

V1

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Vol-Time Spirometry in Restrictive Lung DiseaseV

olu

me

(L)

0

1

2

3

4

5

6

Time (s)0 1 2 3 4

Restrictive Lung Disease: Total Volume reduced and

FVC reduced, FEV1 reducedBut FEV1/FVC ratio =

NORMAL!

FE

V1

For

ced

Vit

al C

apac

ity

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Spirometry: Flow/Volume Loop

Flo

w (

L s

-1)

Expired Lung Volume (L)0

2

4

6

2

4

6

Exp

irat

ion

Insp

irat

ion

1 2 3 4 5

FEF75

FEF 25

Vital Capacity

1 s mark

Measurement of flow rates; contemporary technique

● 1 sec

●

PEF

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Spirometry:

Demonstration

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Flow/Volume Loops inObstructive Lung Disease

Flo

w (

L s

-1)

Lung Volume (L)

0

2

4

6

2

4

6

Exp

irat

ion

Insp

irat

ion

1 2 3 4 5

FEF50

FIF50

●

● 1 sec

PEF

Scooped out appearance

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Flo

w (

L s

-1)

Lung Volume (L)

0

2

4

6

2

4

6

Exp

irat

ion

Insp

irat

ion 1 2 3 4 5

FEF50

FIF50

● 1 sec

●

PEF

Flow/Volume Loops inRestrictive Lung Disease

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Chronic Bronchitis

Clinical definition: “A cough productive of sputum on most days for three months of the

year, for at least two consecutive years”- WHO- CD10

• Airways show Hypersecretion of mucus with mucus gland Hyperplasia = an increase in airflow

resistance in the large airways

• The airway obstruction is due to Luminal Narrowing and Mucus Plugging

Could be part of underlying disease process; eg asthma, cystic fibrosis,Dyskinetic cilia syndrome…etc – Not 1ry diagnosis

Chronic Obstructive Lung Diseases (COPDs)

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Chronic Bronchitis

Metaplasia:Ciliated Columnar Ep cells Replaced by SquamousEp cells

Hypertrophy of submucosal glands & Hyperpalsiaof goblet cells

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Chronic BronchitisChronic Bronchitis leads to:

1. Alveolar Hypoventilation 2. Hypoxaemia (low arterial PO2) 3. Hypercapnia (↑blood CO2) 4. Respiratory Failure may occur

• Individuals are typically cyanosed but may not have Dyspnoea (Respiratory distress)

• In some cases chronic bronchitis may lead to Hypoxic Pulmonary Vasoconstriction, and Secondary Pulmonary Hypertension

• This may lead to right sided heart failure

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Emphysema• Permanent enlargement (dilation) of any part respiratory

acinus (distal to the bronchi)

• Destruction of alveolar walls (without scarring)

• Loss of elastic recoil in the lungs as the respiratory tissue is destroyed

• Thus: area for gas exchange is reduced

• There are two patterns: 1. CENTRIACINAR 2. PANACINAR

Acinus = Terminal duct + alveoli

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The Acinus in Emphysema

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Emphysema

Acinus in Emphysema

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Air trapping,Increased RV

Emphysema

Increased FRC, TLC

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Emphysema

• Proposed to be caused by unregulated activity of extracellular proteases secreted from inflammatory cells

• This is a response to chronic exposure to cigarette smoke or other inhaled irritants

• Linked to an imbalance of protease and the protease inhibitor 1-antitrypsin

• Proteases (particularly Elastase) cause the breakdown of alveolar walls and collapse of small airways

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Aetiology of Emphysema

Antielastaseactivity

1 AntitrypsinDeficiency

(genetic)

Smoking

ElastaseElastic Damage

Emphysema

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Emphysema

• The classic presentation = barrel-chested and dyspnoeic

• Patients have prolonged expiration and may sit forward in a hunched position attempting to squeeze the air out of the lungs

• The loss of elastic recoil and structural support leads to:

1. Trapping of air in lungs 2. Over inflated lungs 3. Decreased rate of airflow on expiration

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Emphysema• Reduced oxygen uptake despite increased

ventilation

• blood oxygenation may be maintained by rapid respiration, but subjects breathless on the slightest exertion and become hypoxic

• Patients are known as ‘PINK PUFFERS’

• Cyanosis, hypercapnia and cor pulmonale (enlargement of the right ventricle) occur late in the disease after progressive decline in lung

function

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• Emphysema progresses slowly and worsens over time.

• Increased effort in breathing leads to progressive breathlessness

• Some do not progress (Pink Puffers)

• In some cases the disease progresses leading to chronic hypoxia and hypercapnia (Blue

Bloaters)

Emphysema

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Effects of Obstructive Disease on Lung Volumes

• TLC is elevated (why?)• Residual Volume is elevated• Expiratory Capacity is elevated• So FRC is elevated (What about IRV & IC?)

Elevations are due to air trapped in lungs following expiration

• Vital capacity may be reduced• FEV1 is reduced

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Effects of Obstructive Disease on Lung Volumes• Airflow is reduced due to airway obstruction.

• VC and FEV1 are reduced but FEV1 is > FVC

Therefore FEV1/FVC ratio is much lower than the normal 70% - 80% of FVC (as low as 25%)

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Restrictive Lung Diseases

• Restrictive lung diseases are caused by a reduction in total lung capacity• Features include:

1. Increased Lung Density (Stiff Lung).

3. Reduced Compliance (V/P)

4. Breathlessness (Dyspnoea) 5. Greater Effort to Inflate Lungs 6. Abnormality of Alveolar Walls which renders them rigid

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Restrictive Lung Diseases

• Characterised by damage to the alveolar walls and capillaries

• An increase in interstitial fluid or fibrosis produce a stiff lung

• Damage to the alveolar epithelium and vasculature produce abnormalities in the ventilation/ perfusion ratio (normally 5/6 ~ 0.8)

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Restrictive Lung Disease• ACUTE - Adult Respiratory Distress Syndrome (ARDS) Trauma or acute illness Inflammation of lung paranchyma- pulmonary edema- eg

Pneumonia• CHRONIC - Pneumoconiosis- occupational lung disease- Asbestosis

silicosis, byssinosis (cotton dust) - Idiopathic Pulmonary Fibrosis (IPF)-unknown

cause - Sarcoidosis- immune system disorder-

small inflammatory nodules (granulomas)- leading to fibrosis

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Chronic Restrictive Lung Diseases

• Develop over months/years and leads to a slowly decreasing respiratory efficiency

• With chronic interstitial fibrosis leading to ‘honeycomb’ lung

• There is an infiltration of macrophages and microcyst formation.

• Clinically patients exhibit dyspnoea, cough and in advanced cases hypoxemia and cyanosis, eventually respiratory failure

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Honeycomb lung

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Proposed Mechanism for Fibrosis

T Lymphocyte

BLymphocyte

ActivatedMacrophage

Unknown Antigen

Immune complexes

cytokines

Oxidants & Proteases

Injury to type I pneumocytes (epithelial cells)

Fibrogenic cytokines

Fibrogenic cytokines

Fibroblasts

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Macrophage in alveolus

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Effects of Restrictive Disease on Lung Volumes

• Reduced FVC• Reduced FEV1

• Relatively Normal FEV1/FVC ratio• Relatively Normal PEFR

• TLC is reduced (Why?)• Inspiratory capacity is reduced.• Residual Volume is normal

Reflect loss of compliance

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Respiratory Function Tests – Diagnostic Significance

• Peak Expiratory Flow Rate - Reduced with obstructive lung disease.• FEV1- * Reduced with obstructive disease * Reduced with pulmonary fibrosis (restrictive)

• Forced Vital Capacity (FVC) - * Reduced in COPD

* Reduced with a corresponding decrease in total lung volume in fibrosis or oedema

* Reduced with muscle weakness

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Respiratory Function Tests – Diagnostic Significance

Forced Expiratory Ratio: FEV1/FVC -

* Low in obstructive lung disease

* Normal or high in restrictive defects

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Thanks &

Good Luck!