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Respiratory Disorders II

Respiratory Disorders II. Lecture Outline. 1- 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.

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Respiratory Disorders II

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  1. Respiratory Disorders II

  2. Lecture Outline 1- 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

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

  4. Spirometry- Vol/Time From fully inspired state patient expels all air in their lungs as forcefully as possible Normally, FEV1/FVC ratio= 0.8 or FEV1 = 80% FVC 6 5 4 75% Volume (L) Forced Vital Capacity FVC 3 FEV1 2 Slope of the initial line gives the flow rate FEF25% -75% 25% 1 0 0 1 2 3 4 Time (s)

  5. 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

  6. Vol-Time Spirometry in Obstructive Lung Disease 6 5 Obstructive Lung Disease Total Volume (TLC and FVC) may be normal but FEV1 is reduced And FEV1/FVC ratio <0.8 (<50% here) 4 Volume (L) 3 Forced Vital Capacity 2 FEV1 1 0 0 1 2 3 4 Time (s)

  7. Vol-Time Spirometry in Restrictive Lung Disease 6 Restrictive Lung Disease: Total Volume reduced and FVC reduced, FEV1 reduced But FEV1/FVC ratio = NORMAL! 5 4 Volume (L) Forced Vital Capacity 3 2 FEV1 1 0 0 1 2 3 4 Time (s)

  8. Spirometry: Flow/Volume Loop Measurement of flow rates; contemporary technique PEF FEF 25 6 ● 1 sec 4 FEF75 1 s mark Expiration ● 2 Expired Lung Volume (L) Flow (L s-1) 0 1 2 3 4 5 2 Inspiration Vital Capacity 4 6

  9. Spirometry: Demonstration

  10. Flow/Volume Loops inObstructive Lung Disease 6 PEF 4 FEF50 ● 1 sec Expiration 2 ● Flow (L s-1) 0 Lung Volume (L) 1 2 3 4 5 2 Inspiration 4 Scooped out appearance FIF50 6

  11. Flow/Volume Loops inRestrictive Lung Disease 6 PEF FEF50 4 ● 1 sec Expiration 2 ● Flow (L s-1) 0 Lung Volume (L) 1 2 3 4 5 2 Inspiration 4 FIF50 6

  12. Chronic Obstructive Lung Diseases (COPDs) 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 MucusPlugging Could be part of underlying disease process; eg asthma, cystic fibrosis, Dyskinetic cilia syndrome…etc – Not 1ry diagnosis

  13. Chronic Bronchitis Hypertrophy of submucosal glands & Hyperpalsia of goblet cells Metaplasia: Ciliated Columnar Ep cells Replaced by Squamous Ep cells

  14. Chronic Bronchitis Chronic 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

  15. 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

  16. The Acinus in Emphysema

  17. Emphysema Acinus in Emphysema

  18. Emphysema Air trapping, Increased RV Increased FRC, TLC

  19. 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 proteaseand the protease inhibitor 1-antitrypsin • Proteases (particularly Elastase) cause the breakdownof alveolar walls and collapse of small airways

  20. Antielastase activity Smoking Elastic Damage Elastase Emphysema Aetiology of Emphysema 1 Antitrypsin Deficiency (genetic)

  21. 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

  22. 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

  23. Emphysema • 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)

  24. 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

  25. 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%)

  26. 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

  27. 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)

  28. 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

  29. 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 caseshypoxemia and cyanosis, eventually respiratory failure

  30. Honeycomb lung

  31. Proposed Mechanism for Fibrosis Unknown Antigen T Lymphocyte B Lymphocyte Activated Macrophage cytokines Immune complexes Fibrogenic cytokines Fibrogenic cytokines Fibroblasts Oxidants & Proteases Injury to type I pneumocytes (epithelial cells)

  32. Macrophage in alveolus

  33. 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

  34. 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

  35. Respiratory Function Tests – Diagnostic Significance Forced Expiratory Ratio: FEV1/FVC - * Low in obstructive lung disease * Normal or high in restrictive defects

  36. Thanks & Good Luck!

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