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The Respiratory System By Farah Ali and Ose Inegbedion Session Breakdown o Anatomy of the Respiratory System o Anatomy of the thorax and airways o Analysis of chest x-rays o Physiology of the Respiratory System o Important histology o Gas exchange and mechanisms of breathing o Ventilation and perfusion o Acid base balance o Pathology of the Respiratory System o Asthma, COPD, Infections, Cancers and other diseases The Thorax The thorax is made up of 3 major parts, which are the: o Thoracic cage o Ribs 1-7 are known as true ribs (they attach directly to the sternocostal joints) o Ribs 8-10 are known as false ribs (they do not attach directly, instead have interchondral joints) o Ribs 11 & 12 are known as floating ribs (they are suspended by muscles and do not attach to sternum) o Thoracic wall consisting of: o External intercostal muscle (involved in inspiration along with diaphragm) o Internal intercostal muscle (involved in expiration along with abdominal wall muscles) o Innermost intercostal muscle o Thoracic cavity o Protects vital organs in the mediastinum such as the heart, lungs, trachea, oesophagus o Provides a passage for structures passing from the head to the abdomen. The diaphragm Contraction of the diaphragm causes it to move down, leading to inspiration Relaxation of the diaphragm causes it to move up, leading to expiration o Arterial supply of the diaphragm: phrenic artery o Venous drainage: brachiocephalic vein, azygous vein and inferior vena cava o Innervation: phrenic nerve The innervation of the diaphragm is clinically important because shoulder pain can be referred pain from the diaphragm, due to the shared roots C3-C4 between the phrenic and supraclavicular nerves. The diaphragm has specific structures which run through at various levels. These are: o T8: Inferior vena cava o T10: Oesophagus o T12: Aortac Question Time! 1) Which of the following is the smallest subdivision of the bronchial tree? A) Alveolar ducts B) Bronchioles C) Terminal bronchioles D) Respiratory bronchioles 2) Which muscle is primarily responsible for increasing the volume of the thoracic cavity during inspiration? A) Diaphragm B) External intercostals C) Internal intercostals D) Rectus abdominis 3) Which of the following structures is not found within the mediastinum? A) Heart B) Thymus gland C) Oesophagus D) Diaphragm Answers 1) Which of the following is the smallest subdivision of the bronchial tree? A) Alveolar ducts B) Bronchioles C) Terminal bronchioles D) Respiratory bronchioles 2) Which muscle is primarily responsible for increasing the volume of the thoracic cavity during inspiration? A) Diaphragm B) External intercostals C) Internal intercostals D) Rectus abdominis 3) Which of the following structures is not found within the mediastinum? A) Heart B) Thymus gland C) Oesophagus D) Diaphragm Chest X-rays When looking at X-rays, remember to adopt the ABCDE approach: A – Airway (is the trachea deviated, can you identify the bronchi) B – Breathing (are the lungs clear or is there consolidation, are the lungs collapsed, are there opacities) C – Cardiac (does the heart appear enlarged, can you identify the borders of the heart) D – Diaphragm (can you identify the costophrenic angles clearly or have they been disfigured) E – Everything else (any soft tissue, valves, pacemakers, piercings, leads)Chest X-rays The following chest X ray shows pleural effusion in the right lung. There is dense white opacification in the lower section of the right lung, and there is a loss of the costophrenic angles due to the buildup of fluid in the lungs. The heart borders have also disappeared on that side.Chest X-rays The following chest X ray shows consolidation. This can be due to pneumonia, other chest infections or malignancies. There is a cloudy appearance in the right lung. It is important to identify consolidation so that other tests can be done to identify the cause, eg infection or cancers.Chest X-rays The following chest X ray shows hyperinflation. The common sign seen in X-rays is a barrel-like appearance of the chest due to the inflation. The lungs appear much larger, the diaphragm is flatter and the costophrenic angles are blunted. This sort of X-ray is commonly seen in patients suffering with COPD (chronic obstructive pulmonary disease) but can be also seen in those with severe asthma.Chest X-rays The following chest X ray shows things that can be seen in addition to normal. Possible things that can be seen are: - Soft tissues - Tubes - ECG leads or central line - Pacemakers - Body piercings Question Time! 1) A chest X-ray demonstrates a rounded opacity with well-defined borders in the right lower lobe. What is the most likely diagnosis? A) Atelectasis B) Pleural effusion C) Pneumonia D) Pulmonary nodule (tumour) 2) What is the term for the radiographic appearance of widened intercostal spaces with flattening of the diaphragms seen in obstructive lung disease? A) Barrel chest B) Pectus excavatum C) Kyphoscoliosis D) Flail chest 3) On a chest X-ray, what term describes a collection of air within the pleural space causing a collapse of the lung? A) Pneumothorax B) Pleural effusion C) Atelectasis D) Consolidation Answers 1) A chest X-ray demonstrates a rounded opacity with well-defined borders in the right lower lobe. What is the most likely diagnosis? A) Atelectasis B) Pleural effusion C) Pneumonia D) Pulmonary nodule (tumour) 2) What is the term for the radiographic appearance of widened intercostal spaces with flattening of the diaphragms seen in obstructive lung disease? A) Barrel chest B) Pectus excavatum C) Kyphoscoliosis D) Flail chest 3) On a chest X-ray, what term describes a collection of air within the pleural space causing a collapse of the lung? A) Pneumothorax B) Pleural effusion C) Atelectasis D) ConsolidationImportant histology of the lungs o The trachea of the lungs contain pseudostratified ciliated columnar epithelium, and has a ring of hyaline cartilage for support o As you move from the trachea to the bronchioles, you lose the cartilage and instead is replaced with a ring of smooth muscle. o In the alveoli, there are two main of cells: o Type 1 pneumocytes (simple squamous) involved in gas exchange o Type 2 pneumocytes (cuboidal) involved in surfactant production o There are also dust cells (macrophages) and club cells involved in immune response and contain enzymes. Gas exchange o As oxygen passes from the air into the blood it has to diffuse through surfactant, epithelial cells, the basement membrane, red blood cells and finally bind to haemoglobin. o Haemoglobin is made of 4 subunits (an Fe in each), and there are various factors that can affect binding of haemoglobin to oxygen such as: o pH o Temperature o 2,3 BPG o On an oxygen dissociation curve, these factors will shift the sigmoidal curve either to the left (increasing affinity, or to the right (lower affinity) o Fetal haemoglobin has a very high affinity for oxygen and so it’s curve is shifted to the leftBreathing o Breathing is controlled by certain chemoreceptors, and each have a different role: o Central chemoreceptors (found in medulla oblongata) detect pH changes and partial pressure of CO2 o Peripheral chemoreceptors (found in carotid and aortic bodies) detect partial pressure of O2 o The importance of the body to detect changes in partial pressures helps the body to acclimatize to different environments, such as high altitudes, which has low O2, causing the body to increase respiration in response.Restrictive vs Obstructive Diseases o Before covering its important to define a couple key terms: o FEV1: Maximum amount of air that can be forcefully exhaled / expired over 1 second following maximal inhalation/inspiration. o FVC: The total amount of air that can be forcefully exhaled in one breath. o The FEV1/FVC ratio is normally 0.7 (70%) o If the ratio is less than 70%, then this indicates an obstructive issue due to narrowing of airways. o If the ratio is greater than 70%, then this is a restrictive issue due to scarring or fibrosis. Ventilation and Perfusion o Naturally, arterial pressure in the lungs is highest at the base compared with the apex of the lungs (gravity). o Ventilation refers to the process of air movement into and out of the lungs, whereas perfusion refers to the circulation of blood within the pulmonary capillaries, facilitating gas exchange in the lungs. o Mismatch can occur when either ventilation or perfusion is abnormal: o If ventilation is abnormal, it can be due to pulmonary oedema or bronchoconstriction o If perfusion is abnormal, it can be due to a pulmonary embolism. o If ventilation/perfusion mismatch continues it can lead to: o Type 1 Respiratory failure (low O2, CO2 normal) o Type 2 Respiratory failure (low O2, high CO2) o This can be due to hypoventilation seen in COPD, fibrosis, obesity and pneumonia.Acid-Base Regulation o pH in the body is controlled in short term by the respiratory system, and long term by the renal system. o pH disorders are categorized into either metabolic or respiratory. o Metabolic o Acidosis: Low levels of bicarbonate o Alkalosis: High levels of bicarbonate o Respiratory o Acidosis: High levels of carbon dioxide o Alkalosis: Low levels of carbon dioxide o Compensation will occur in the opposite system Question Time! 1) Which component of the respiratory system is responsible for producing surfactant? A) Type I pneumocytes B) Type II pneumocytes C) Alveolar macrophages D) Clara cells 2) A patient presents to the emergency department with shortness of breath, tachypnoea, and confusion. Arterial blood gas (ABG) analysis reveals a pH of 7.30, partial pressure of carbon dioxide (PaCO2) of 60 mmHg, partial pressure of oxygen (PaO2) of 60 mmHg, and bicarbonate (HCO3-) of 30 mEq/L. What is the most likely interpretation of these ABG results? Normal ranges are: pH: 7.35 to 7.45 (PaCO2): 35 to 45 mmHg (PaO2): 75 to 100 mmHg (HCO3-): 22 to 26 mEq/L A) Respiratory acidosis B) Respiratory alkalosis C) Metabolic acidosis D) Metabolic alkalosis Answers 1) Which component of the respiratory system is responsible for producing surfactant? A) Type I pneumocytes B) Type II pneumocytes C) Alveolar macrophages D) Clara cells 2) A patient presents to the emergency department with shortness of breath, tachypnoea, and confusion. Arterial blood gas (ABG) analysis reveals a pH of 7.30, partial pressure of carbon dioxide (PaCO2) of 60 mmHg, partial pressure of oxygen (PaO2) of 60 mmHg, and bicarbonate (HCO3-) of 30 mEq/L. What is the most likely interpretation of these ABG results? Normal ranges are: pH: 7.35 to 7.45 (PaCO2): 35 to 45 mmHg (PaO2): 75 to 100 mmHg (HCO3-): 22 to 26 mEq/L A) Respiratory acidosis B) Respiratory alkalosis C) Metabolic acidosis D) Metabolic alkalosis Asthma o Asthma is a chronic obstructive lung disease. It is caused by episodic bronchoconstriction and reversible airway obstruction due to hypersensitivity to environmental factors. o Several changes occur to the airways: o Reversible narrowing of the airways o Inflammation o Smooth muscle hypertrophy o Goblet cell hyperplasia o In between attacks it is asymptomatic, but during an attack a patient can experience: o Dyspnoea (shortness of breath) o Coughing o Wheezing o Chest tightness o Usually presents as the atopic triad: hay fever, eczema and asthmaAsthma treatment o Asthma can be treated by two main subtypes of treatment o Bronchodilators: o Short acting beta agonists such as salbutamol o Long acting beta agonists such as salmeterol o Muscarinic antagonists such as ipratropium bromide o Anti-inflammatories: o Corticosteroids such as beclomethasone o Antileukotrienes such as montelukast o Management of an acute asthma attack: o Oxygen o High dose nebulised salbutamol o Hydrocortisone o ipratropium bromide Chronic Obstructive Pulmonary Disease o Although Asthma and COPD are both obstructive, a key difference is that COPD is irreversible narrowing of the airways and encompasses both chronic bronchitis and/or emphysema. o Factors that influence are heavy smoking and having thea1 antitrypsin deficiency o Emphysema (destruction of alveolar walls and capillaries involved in gas exchange) o No cough or peripheral oedema o Can be breathless o Very quiet breathing sounds o Chronic bronchitis (inflammation of bronchial mucosa leaving to hypersecretion of mucus) o Cyanosis o Chronic productive cough for at least 3 months every year o Crepitations o May have peripheral oedema Chronic Obstructive Pulmonary Disease Treatment o In general, management can include: o Smoking cessation o Influenza vaccine o Pulmonary rehabilitation o If the above management does not help: o Oral theophylline’s o Oral antibiotic therapy o Mucolytics o Diuretics for oedema o Management of acute COPD: o Oxygen o High dose nebulised bronchodilators o Oral or IV steroids o Antibiotics Pneumonia o Pneumonia is an infection that causes inflammation of lung tissues and is seen as consolidation on chest x-rays. o Common symptoms and signs patient present with: o Shortness of breath o Productive cough and chest pain o Fever o Haemoptysis o Tachycardia o Tachypnoea o Organisms that can cause it: o Typical – Streptococcus pneumoniae o Atypical – Mycoplasma pneumoniae o Viral – Rhinovirus o Nosocomial – Pseudomonas o Fungal – Pneumocystis Pneumonia Treatment o After doing a chest xray, it is important to do a sputum or blood culture to confirm that Pneumonia is the cause of the infection. An ABG can also be done to check for hypoxia. o Basic treatment of pneumonia is: o Antibiotics for the infection o Oxygen of hypoxic o IV fluids if dehydrated o If the infection is much worse and patient appears in distress, complete a CURB-65 score o Confusion o Urea over 7 o Respiratory rate over 30 o Blood pressure: systolic less than 90 and diastolic less than 60 o 65 years or older o CURB score of 0-1: home based care, CURB score of 2+: the patient should be admitted to hospital. Tuberculosis o Tuberculosis is an infection caused by Mycobacterium tuberculosis. It forms cavitary lesions in upper lobes and as a result granulomas form with caseous necrosis in the centre. o Can often be confused with cancer when patient presents due to overlapping symptoms: o Fever o Night sweats o Weight loss o Haemoptysis o Lymphadenopathy o A few risk factors to consider: o Contact with someone who has tuberculosis o Immigrants from or holiday returners from a TB prevalent country o Immunosuppression o IV drug use Tuberculosis Screening and Management o For active cases of tuberculosis, the infection can be identified with a chest x-ray, sputum culture and nucleic acid amplification test (NAAT). o For latent cases of tuberculosis, the Mantoux test can be conducted where tuberculinis injected into the skin to assess the size of thickening that occurs. A positive test shows over 5mm of thickening of the skin. o To help with remembering management, use the acronym RIPE: o Rifampicin o Isoniazid (give B6 supplements alongside this) o Pyrazinamide o Ethambutol o Since tuberculosis is a notifiable disease, it is important to notify as soon as infection is suspected and isolate the patient until full treated. o Also notify and test people who may have been in contact with the infected patient.Lung Cancers Lung cancers are categorized into either: o Small cell lung cancer (20% of cases) o Non-small cell lung cancer (80% of cases) o Adenocarcinoma o Squamous Cell Carcinoma o Large Cell Carcinoma o Common signs and symptoms: o Shortness of breath o Cough and Haemoptysis o Clubbing of fingernails o Weight loss, night sweats, fever o Lymphadenopathy Lung Cancer Treatment o Non-small cell carcinomas are usually more localised than others and so the first line treatment is usually a lobectomy or segmentectomy. o Radiotherapy and chemotherapy are usually used in small cell carcinomas since their prognosis is worse, although they can also be used in non-small cell carcinomas as an adjuvant therapy. o An adjuvant therapy is one that is given before surgeries to reduce the size of tumours whereas a neoadjuvant therapy is given after surgery to improve the likelihood that the treatment works and minimizes the risk of reoccurrence. o Lung cancers can metastasize to the brain, liver, adrenal glands and bones. o Lung cancer can also occur as a result to another cancer occurring elsewhere first, for example breast cancer.Interstitial Lung Disease o Interstitial lung disease referrers to restrictive conditions that affect the parenchyma of the lungs, which can lead to inflammation and fibrosis. Therefore, their FEV1/FVC ratio is greater than 0.7 (70%) o The most characteristic appearance of interstitial lung disease not seen on x-rays but rather on a chest CT scan where a distinctive “broken glass” appearance is shown. o Causes of this can be: o Hypersensitivity (farmer’s lung) o Pneumoconiosis (particle inhalation) o Drug induced (for example methotrexate) o Idiopathic sarcoidosis and fibrosisAsbestosis o Asbestosis is due to exposure of asbestos, which is a fibrogenic and oncogenic compound. o Those at risk are: o Asbestos miners o Pipe fitters o Roofers and insulation workers o Builders working on boats and ships o The inhalation of asbestos can lead to fibrosis and causes pleural plaques which can be seen on a chest x-ray o Asbestosis also increases the risk of developing mesothelioma or bronchogenic carcinoma later Pleural Effusion o Pleural effusion is categorized by an accumulation of fluid in the pleural cavity and can be classed as either exudative or transudative. On examination can show dull percussion and reduced breath sounds. o Exudative pleural effusion is caused by increased vascular permeability due to inflammation, which in turn causes proteins to leak out of space. It is seen in: o Pneumonia o Tuberculosis o Lung cancers o Rheumatoid Arthritis o Transudative pleural effusion is caused by either low oncotic or high hydrostatic pressures. It is seen in: o Congestive Heart Failure o Hypoalbuminemia o Liver cirrhosis Question Time! 1) Which of the following conditions is characterized by reversible airflow obstruction and is classified as obstructive? A) Asthma B) Restrictive lung disease C) Tuberculosis D) Chronic bronchitis 2) In which respiratory condition is airflow limitation typically progressive and not fully reversible, thus classified as an obstructive lung disease? A) Asthma B) Restrictive lung disease C) Tuberculosis D) COPD 3) Which respiratory condition is characterized by fibrosis and scarring of lung tissue, resulting in decreased lung compliance and classified as a restrictive lung disease? A) Asthma B) Chronic bronchitis C) COPD D) Tuberculosis Answers 1) Which of the following conditions is characterized by reversible airflow obstruction and is classified as obstructive? A) Asthma B) Restrictive lung disease C) Tuberculosis D) Chronic bronchitis 2) In which respiratory condition is airflow limitation typically progressive and not fully reversible, thus classified as an obstructive lung disease? A) Asthma B) Restrictive lung disease C) Tuberculosis D) COPD 3) Which respiratory condition is characterized by fibrosis and scarring of lung tissue, resulting in decreased lung compliance and classified as a restrictive lung disease? A) Asthma B) Chronic bronchitis C) COPD D) Tuberculosis1) Physiology by Robin Preston & Thad E Wilson, published by Walters Kluwer/Lippincott, Williams & Wilkins. 2) Clinical Medicine by Kumar P & Clarke M 3) Gray’s Anatomy for Students by Drake, Vogl and Mitchell 4) Pharmacology by Rang HP, Dale MM, Ritter JM & Moore PK