Respiratory System Pathology Lecture no II

Respiratory Anatomy Review Conducting airways Trachea, bronchi, bronchioles, terminal bronchioles Acinus- consists of respiratory bronchioles, alveolar ducts, and alveoli Vasculature Lungs have dual blood supply: pulmonary and bronchial arteries. Pulmonary arteries give way to an investing network of capillaries Type I and II pneumocytes Macrophages Capillaries completely invest pulmonary parenchyma establishing architecture for transport of gases. Alveolar walls are porous along for movement of substances from one alveolus to another (pores of Kohn) Type II pneumocytes secrete surfactant and are the cells that repair injured alveolar epithelium

Congenital Anomalies Conducting airway anomalies: stenosis, atresia, and tracheoesophageal fistula Can present with dyspnea, infection, failure to thrive Pulmonary hypoplasia- failure of lungs to fully develop Caused by oligohydramnios, and reduced fetal respiratory movements (many etiologies ) Pulmonary sequestration Lung tissue without connection to tracheobronchial tree Extra and intralobar types Blood supply is not from PA but from aortic branch Intralobar sequestration is usually secondary to multiple infections with a subsequent walling off

Atelectasis (Lung Collapse) Atelectasis- collapse of previously inflated lung, producing areas with airless parenchyma Three different types: resorption, compression, and contraction atelectasis Patients can present with dyspnea, chest pain, loss of conciousness, and cyanosis Compression atelectasis can cause sudden death and needs to be treated immediately

Resorption Atelectasis Caused by obstruction of conducting airway (e.g. mucus plugs, foreign bodies, neoplasm ) Air in parenchyma distal to obstruction is slowly reabsorbed , causing mediastinal shift to the site of atelectasis

Compression Atelectasis Clinically most significant Caused by compression of lung parenchyma by a , liquid( fluid or blood ) , or gas within the pleural space or elevation of the diaphragm. –ascitis Pneumothorax Tension pneumothorax Hemothorax Effusion - Cardiac failure Mediatinal shift away from atelectasis Pleural effusions, bullous emphysema rupture- spontaneous pneumothorax Talk about clinical signs and symptoms (hyperresonance, JVD, tracheal deviation, medias. shift) Clinical anecdote- lady that had NG tube pushed through bronchus

Contraction Atelectasis Caused by fibrosis of lung parenchyma preventing expansion Changes can be focal or diffuse Usually not treatable Fibrosis can be caused by radiation, infection, toxic injury, or systemic disease

Pulmonary Edema Two primary etiologies: hemodynamic and microvascular injury Hemodynamic edema- increased vascular hydrostatic pressure or decreased oncotic pressure (Starling forces) Microvascular injury- increased permeability of capillaries secondary to injury of endo- or epithelial cells Edema is usually localized, but diffuse edema can occur leading to more serious complications Grossly the lungs appear boggy, heavy, and have a brown color. Patients present with SOB. Hemodynamic- vascular hydrostatic pressure-left sided heart failure, volume overload, pulmonary vein obstruction decreased oncotic- hypoalbunemia, nephrotic syndrome, liver disease Microvascular injury- infection, shock or trauma, inhaled toxic gases, liquid aspiration, radiation, drugs, TRALI Other presentations can be the underlying cause (e.g. pneumonia with edema presents with pneumonia symptoms)

Acute Respiratory Distress Syndrome (ARDS) ARDS is caused by diffuse damage to the pulmonary capillary vasculature with subsequent sequelae. ARDS is a syndrome caused by a lot of insult from diseases or conditions (infection, trauma, chemical injury, pancreatitis, gas toxicity, etc.) Usually they are multiple contributing factors to the development of ARDS The majority of ARDS cases are due to sepsis, pulmonary infections, gastric aspiration, and mechanical trauma Remember ARDS is a syndrome and not a single disease entity

Acute Respiratory Distress Syndrome (ARDS) Clinical manifested as Acute onset of dyspnea no responding to oxygen therapy . Decrease arterial oxygen pressure ( hypoxemia ) Bilateral pulmonary infiltration on chest X ray examination . In the absence of heart failure .

Pathogenesis of ARDS Capillary damage with increased permeability Increase in inflammatory proteins Migration of inflammatory cells (i.e. neutrophils) End result is diffuse damage to capillaries, alveoli, and terminal bronchioles

ARDS and Diffuse Alveolar Damage The pathologic correlate to ARDS is Diffuse Alveolar Damage (DAD) Histology shows: hyaline membranes, proteinaceous debris, and desquamated cells

ARDS Outcomes There are approximately 150,000 cases of ARDS per year with a mortality rate of about 60%. Even in patients that survive ARDS, there are still long term complications. They are scarring, contraction atelectasis, and consolidation. These long term changes are usually focal. ARDS presents with profound dyspnea, respiratory distress, and chest x-ray showing diffuse bilateral infiltrates (honeycombing in organized phase)

Obstructive and Restrictive Diseases Obstructive and Restrictive Disease are two large classes of pulmonary disease. Based on pulmonary function and derangement Obstructive disease- increased resistance to airflow. FEV1 is decreased while FVC is normal ( FEV1 to FVC ratio is decrease) Restrictive disease- ability of lungs to expand is compromised. Total lung volume is decreased. FVC is decrease and FEV1 decease proportionaly (so the FEV1 to FVC ratio near normal ) Many diseases have components of both obstructive and restrictive but there is usually an overriding appearance

In summary Obstructive and Restrictive Pulmonary Diseases Diffuse pulmonary diseases are divided into: 1. Obstructive disease: characterized by limitation of airflow owing to partial or complete obstruction at any level from trachea to respiratory bronchioles. Pulmonary function test: limitation of maximal airflow rate during forced expiration (FEVI). 2. Restrictive disease: characterized by reduced expansion of lung parenchyma with decreased total lung capacity while the expiratory flow rate is near normal. Occur in: 1. Chest wall disorder. 2. Acute or chronic, interstitial and infiltrative diseases, e.g. ARDS and pneumoconiosis.

Obstructive and Restrictive Diseases Emphysema, chronic bronchitis, bronchiectasis, and asthma are obstructive diseases Restrictive diseases are wide ranging and are either extrinsic to the lung (e.g. neuromuscular, kyphosis, obesity) or intrisic (e.g. DAD, fibrosis, sarcoidosis ) Many diseases have components of both obstructive and restrictive but there is usually an overriding appearance

Chronic Obstructive Pulmonary Disease (COPD) Share a major symptom: dyspnea with chronic or recurrent obstruction to airflow within the lung. The incidence of COPD has increased dramatically in the past few decades.

Chronic Obstructive Pulmonary Disease (COPD) Related diseases Chronic bronchial outflow obstruction Overlapping features

Chronic Obstructive Pulmonary Disease (COPD) COPD is the clinical term given to those with overlapping emphysema and bronchitis The vast majority of people with COPD are smokers (90%), and the other 10% have a high exposure rate to second hand smoke or live in an area with increased rates of air pollution COPD is becoming increasingly prevalent due to the increase in pollution and smoking COPD is the fourth leading cause of morbidity in the word .

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