Obstructive & Restrictive Disorders Notes PDF

BMED13-125: Exploring Human Disease Obstructive and Restrictive Disorders Dr Donna Sellers  Session Learning Objectives LO1. Outline measurements of ventilatory function LO2. Recognise and explain the characteristics of obstructive airway disorders LO3. Recognise and expl...

BMED13-125: Exploring Human Disease Obstructive and Restrictive Disorders Dr Donna Sellers  Session Learning Objectives LO1. Outline measurements of ventilatory function LO2. Recognise and explain the characteristics of obstructive airway disorders LO3. Recognise and explain the characteristics of restrictive airway disorders Useful texts: Marieb & Hoehn, 12th Ed., Chapter 22 Guyton & Hall, 14th Ed., Chapters 38-43 MEASURING VENTILATORY FUNCTION Spirometry – measuring ventilatory function Volume/time curve (spirogram)  VC, FVC, FEV1 calculated manually Flow/volume loop (spirogram)  Used more commonly clinically Portable spirometers  automatically calculate indices  stores patient data, calculates ref values Peak flow meters  peak expiratory flow (PEF)  patient use **Watch the VOPs in iLearn on www.chemistaustralia.com.au how to interpret spirometry LO1. Outline measurements of ventilatory function  Performing Spirometry https://www.nationalasthma.org.au/living-with-asthma/how-to-videos/performing-spirometr y-in-primary-care LO1. Outline measurements of ventilatory function  Pulmonary Volumes and Capacities 4 volumes 4 capacities Inspiratory reserve volume Inspiratory 3100 ml capacity 3600 ml Vital Total lung capacity capacity 4800 ml 6000 ml Tidal volume 500 ml Expiratory reserve volume Functional 1200 ml residual capacity Residual volume 2400 ml 1200 ml (a) Spirographic record for a male LO1. Outline measurements of ventilatory function Pulmonary Volumes and Capacities LO1. Outline measurements of ventilatory function INTRODUCTION TO AIRWAY DISORDERS  Airway disorders  Often separated into obstructive and restrictive on basis of the underlying functional changes observed  Many respiratory disorders show aspects of both types  Often see patients with multiple respiratory disorders Obstructive disorders  Characterised by airway obstruction, increased resistance to airflow, which results in reduced airflow, particularly during expiration  More force is required to expel air, emptying is slower, due to partial or complete obstruction in airways  In spirometry tests, revealed by  decreased FEV1, decreased FEV1 / FVC ratio, (FVC unchanged)  Wheezing is a common sign  eg asthma, chronic bronchitis, emphysema LO2. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Airway disorders Restrictive disorders  Reduced expansion of the lung parenchyma and decreased total lung capacity  Characterised by decreased FVC, while the FEV /FVC ratio is 1 often normal  Includes pneumonia, tuberculosis, some occupational lung diseases (eg. asbestosis)  Chest wall disease (eg. polio, obesity, pleural disease), chronic interstitial and infiltrative disease - fibrosis LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders Airway disorders - Spirometry LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders Airway disorders - Spirometry Pierce, R and Johns, DP, Spirometry: The Measurement and Interpretation of Ventilatory Function in Clinical Practice LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Obstructive and restrictive defects summarised Normal Obstructive Restrictive Mixed FVC N or N FEV1 N or N FEV1/FVC N or N Spirogram Bronchodilator Not usually Significant >12% Not usually Significant >12% response Image source: National Asthma Council LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Obstructive Disorders Limitation in maximal expiratory flow rate during forced expiration (↓ FEV1) Expiratory obstruction may result from:  anatomic airway narrowing or  loss of elastic recoil of the lung Chronic Obstructive Pulmonary  Emphysema Disease (COPD)  Chronic bronchitis  Asthma  Bronchiectasis LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  COPD  Exemplified by chronic bronchitis and emphysema  Irreversible decrease in the ability to force air out of the lungs  Other common features  History of smoking in 80% of patients  Dyspnea  Coughing and frequent pulmonary infections  Periods of increased symptoms (acute exacerbations)  Most patients develop respiratory failure (hypoventilation) accompanied by respiratory acidosis https://lungfoundation.com.au/resources/copd-x-concise-guide/ LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders Chronic bronchitis  Obstruction is persistent and largely irreversible due to mucus secretion and airway thickening as a result of chronic inflammation Emphysema  Abnormal permanent destruction of alveolar walls caused by chronic infection, mucus production, entrapment of air  Variable, relative degree of bronchiolar obstruction vs lung parenchyma destruction LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders COPD Tobacco smoke Air pollution a-1 antitrypsin deficiency Continual bronchial Breakdown of elastin in irritation and inflammation connective tissue of lungs Chronic bronchitis Emphysema Bronchial edema, Destruction of alveolar chronic productive cough, walls, loss of lung bronchospasm elasticity, air trapping Airway obstruction or air trapping Dyspnea Frequent infections Abnormal ventilation- perfusion ratio Hypoxemia Hypoventilation LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Chronic Bronchitis  Obstruction is persistent and largely irreversible  Inhaled irritants cause hypersecretion of mucus due to hypertrophy of submucosal glands in trachea and bronchi  Hyperplasia of goblet cells in small airways  Inflammation of the bronchi & bronchioles  Fibrosis, airway thickening  Obstruction - FEV1  Impaired ventilation and gas exchange  Cough, productive cough, wheezing and breathlessness LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Emphysema  Permanent enlargement of alveoli  Destruction of alveolar walls causes distension of lung tissue - hyperinflation  Loss of elasticity without fibrosis  Accessory muscles used to breathe  Leads to exhaustion as increased total body energy required  Bronchioles open during inspiration but close during expiration  Causes air trapping in the alveoli - hyperinflation  Damage to pulmonary capillaries, loss of surface area for gas exchange LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Clinical phenotypes of COPD “Blue bloater"  Primary underlying pathology is chronic bronchitis  Pulmonary capillary bed is undamaged, but airway obstruction causes alveolar hypoxia  Dreadful ventilation-to-perfusion mismatch leading to hypoxemia and polycythemia, and increased carbon dioxide retention (hypercapnia)  Alveolar hypoxia causes pulmonary vasoconstriction to divert blood flow, and results in pulmonary hypertension, decreased CO from LV, activation of RAAS, and fluid retention (the “bloating”)  Pulmonary hypertension also leads to right sided heart failure (contributes to bloating)  Worse hypoxemia than pink puffers, leads to bluish lips and faces (cyanosis - the "blue”) LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Clinical phenotypes of COPD “Pink puffer"  Emphysema is primary underlying pathology  Loss of elasticity (air trapping)  Destruction of distal airways & pulmonary capillary bed - reduces surface area for gas exchange  Body compensates by hyperventilation (the "puffer" part)  Arterial blood gases relatively normal because of this compensatory hyperventilation  Matched ventilation-perfusion deficit so less Clinical manifestations do not appear hypoxemia (compared to blue bloaters) & have a until 1/3 of lung parenchyma damaged "pink" complexion (the "pink” part)  Some of pink appearance may also be due to the effort of breathing (use of neck and chest muscles)  Eventually, respiratory effort leads to muscle wasting and weight loss LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  COPD & Right Heart Failure   Pulmonary vascular resistance due to:  Loss of alveolar capillary units  Alveolar hypoxia, secondary to hypoventilation, causes hypoxic vasoconstriction  Remodelling of pulmonary arterial walls   Pulmonary artery pressure   Afterload of right ventricle  Decreased right CO or cor pulmonale  Right ventricular failure secondary to pulmonary hypertension LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  COPD & Oedema  Increased ESV due to right heart failure  Blood not ejected ‘backs up’ into right atrium and systemic veins  Increased systemic venous pressure  Increased capillary hydrostatic pressure  Increased fluid infiltration of the interstitial space - oedema LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders Broad comparison of Bronchitis & Emphysema LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Asthma  obstructive disorder of the airways  intermittent attacks, wheezing,  coughing, dyspnoea, chest tightening  in Australia ~ 40% of people show symptoms  characterised by bronchial constriction, inflammatory changes & bronchial hypersensitivity Acute attacks  severe, need prompt treatment, can be fatal LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Asthma  Asthma is a chronic lung disease, which can be controlled but not cured.  In clinical practice, asthma is defined by the presence of both the following:  excessive variation in lung function (‘variable airflow limitation’, i.e. variation in expiratory airflow that is greater than that seen in healthy people)  respiratory symptoms (e.g. wheeze, shortness of breath, cough, chest tightness) that vary over time and may be present or absent at any point in time.  In young children in whom lung function testing is not feasible, including most preschool children, asthma is defined by the presence of variable respiratory symptoms.  Untreated asthma is usually characterised by chronic inflammation involving many cells and cellular elements, airway hyperresponsiveness, and intermittent airway narrowing (due to bronchoconstriction, congestion or oedema of bronchial mucosa, mucus, or a combination of these).  Asthma probably represents a spectrum of conditions with different pathophysiological mechanisms. In older patients, there may be substantial overlap with the LO5. Recognise features and explain of COPD. the characteristics of obstructive & restrictive airway disorders  Asthma http://www.nlm.nih.gov/medlineplus/magazine/issues/fall11/articles/fall11pg4.html LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Asthma - Classification  currently considered more important to classify asthma on the basis of severity rather than the cause, as it is the severity which determines the treatment rationale LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Bronchiectasis  defined by localized, irreversible dilation of part of the bronchial tree caused by destruction of the muscle and elastic tissue  Congenital or hereditary conditions, including cystic fibrosis  Postinfectious conditions, including pneumonia caused by bacteria, viruses and fungi  Bronchial obstruction, due to tumour, foreign bodies, mucus impaction, in which the bronchiectasis is localized to the obstructed lung segment  Other conditions  eg. rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, and post- transplantation (chronic lung rejection, and chronic graft-versus-host disease after bone marrow transplantation)  Summary – Obstructive Disorders LO5. Recognise and explain the characteristics of obstructive & restrictive airway disorders  Restrictive Disorders Reduced total lung capacity Expiratory flow rate is normal or reduced proportionately Chest wall disorders in the presence of normal lungs Neuromuscular diseases such as polio-myelitis, severe obesity, pleural diseases Acute or chronic interstitial and infiltrative diseases Dust diseases or pneumoconioses, interstitial fibrosis of unknown etiology LO3. Recognise and explain the characteristics of restrictive airway disorders  Asbestos Related Diseases Asbestos A family of crystalline hydrated silicates that form fibres Occupational exposure is linked to: Localised fibrosis plaques Pleural effusion Parenchymal interstitial fibrosis (asbestosis) Lung carcinoma Mesotheliomas LO3. Recognise and explain the characteristics of restrictive airway disorders  Pathogenesis of Asbestosis Concentration, size, shape and solubility of different forms of asbestos dictate it’s ability to cause disease Serpentine Most asbestos used in industry More likely to be removed by mucociliary escalator More soluble – gradually leached from tissue Amphibole Less prevalent but more pathogenic Align themselves in air stream Delivered deeper into lungs Penetrate epithelial cells Reach interstitium Mesothelioma BOTH ARE FIBROGENIC – INCREASING DOSES ASSOCIATED WITH HIGHER INCIDENCE OF ALL ASBESTOS RELATED DISEASES LO3. Recognise and explain the characteristics of restrictive airway disorders  Asbestosis Diffuse pulmonary interstitial fibrosis  Presence of asbestos bodies  Consist of asbestos fibres coated with an iron-containing proteinaceous material  Macrophages attempt to phagocytose asbestos fibres  Begins as fibrosis around respiratory bronchioles and alveolar ducts  Then extends to involve alveolar sacs and alveoli creating enlarged air spaces enclosed within thick fibrous walls – honeycombed LO3. Recognise and explain the characteristics of restrictive airway disorders Agent Disease Exposure MINERAL DUSTS Coal dust Anthracosis Coal mining (particularly hard coal) Macules Progressive massive fibrosis Caplan syndrome Silica Silicosis Foundry work, sandblasting, hard rock mining, stone Caplan syndrome cutting, others Asbestos Asbestosis Mining, milling, fabrication, and installation and removal Pleural plaques of insulation Caplan syndrome Mesothelioma Carcinoma of the lung, larynx, stomach, colon Beryllium Acute berylliosis Mining, fabrication Beryllium granulomatosis Lung carcinoma (?) Agent Disease Exposure MINERAL DUSTS Iron oxide Siderosis Welding Barium sulfate Baritosis Mining Tin oxide Stannosis Mining ORGANIC DUSTS THAT INDUCE HYPERSENSITIVITY PNEUMONITIS Moldy hay Farmer's lung Farming Bagasse Bagassosis Manufacturing wallboard, paper Bird droppings Bird-breeder's lung Bird handling ORGANIC DUSTS THAT INDUCE ASTHMA Cotton, flax, hemp Byssinosis Textile manufacturing Red cedar dust Asthma Lumbering, carpentry CHEMICAL FUMES AND VAPORS Nitrous oxide, sulfur dioxide, Bronchitis, asthma Occupational and accidental ammonia, benzene, insecticides exposure Pulmonary edema ARDS Mucosal injury Fulminant poisoning  Session Learning Objectives LO1. Outline measurements of ventilatory function LO2. Recognise and explain the characteristics of obstructive airway disorders LO3. Recognise and explain the characteristics of restrictive airway disorders Useful texts: Marieb & Hoehn, 12th Ed., Chapter 22 Guyton & Hall, 14th Ed., Chapters 38-43