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Pulmonary Pathophysiology Histology of the lung • Respiratory epithelium • Connective tissue fibers, and cartilage: support and maintain open air way • Alveolar cells (type I and type II) Type I pneumocyte Type I pneumocyte Alveolar space Capillary lumen Type II pneumocyte Endothelium Normal Lung Function of the lung • Gas exchange • Protection against infection by alveolar macrophages • Surfactant secretion: allow expansion of alveoli with air Lung function tests • Tidal volume (TV): it is the amount of gas inhaled or exhaled with each resting breath. • Residual volume (RV): it is the amount of gas remaining in the lungs at the end of maximum exhalation. • Vital capacity (VC): it is the total amount of gas that can exhaled following maximum inhalation. • Total lung capacity (TLC): it is the amount of gas in the lung at the end of maximum inhalation. TLC = RV+ VC Reduction of Pulmonary Function • Inadequate blood flow to the lungs: hypoperfusion • Inadequate air flow to the alveoli: hypoventilation Noso-comial infections • Factors that reduce airflow also compromise particle clearance and predispose to infection. • High rate of pneumonia in hospital patients due in large part to impaired ventilation and clearance. • Restricted lung movement and ventilation may arise due to: • Positioning • Constricting bandages • Central nervous system depression • Coma Signs and Symptoms of Pulmonary Disease 1- Dyspnea: subjective sensation of uncomfortable breathing, feeling “short of breath” • Ranges from mild discomfort after exertion to extreme difficulty breathing at rest. • Usually caused by diffuse and extensive rather than focal pulmonary disease. Causes of Dyspnea : – Airway obstruction –Greater force needed to provide adequate ventilation –Wheezing sound due to air being forced through airways narrowed due to constriction or fluid accumulation – Decreased compliance of lung tissue Signs of dyspnea: • Flaring nostrils • Use of accessory muscles in breathing • Retraction (pulling back) of intercostal spaces 2- Cough • Attempt to clear the lower respiratory passages by forceful expulsion of air • Most common when fluid accumulates in lower airways Causes of Cough: • Inflammation of lung tissue • Increased secretion in response to mucosal irritation • Inhalation of irritants • Intrinsic source of mucosal disruption – such as tumor invasion of bronchial wall • Excessive blood hydrostatic pressure in pulmonary capillaries – Pulmonary edema – excess fluid passes into airways • When cough can raise fluid into pharynx, the cough is described as a productive cough, and the fluid is sputum. – Production of bloody sputum is called hemoptysis • Not threatening, but can indicate a serious pulmonary disease –Tuberculosis, lung abscess, cancer, pulmonary infarction. • If sputum is purulent------- infection of lung or airway is indicated. • Cough that does not produce sputum is called a dry, or nonproductive cough. • Acute cough is one that resolves in 2-3 weeks from onset of illness or treatment of underlying condition. • Acute cough caused by upper respiratory tract (URT) infections, allergic rhinitis, acute bronchitis, pneumonia, congestive heart failure, pulmonary embolus, or aspiration. • A chronic cough is one that persists for more than 3 weeks. • In nonsmokers, almost always due to postnasal drainage syndrome, asthma, or gastroesophageal reflux disease • In smokers, chronic bronchitis is the most common cause, although lung cancer should be considered. 3- Cyanosis • When blood contains a large amount of unoxygenated hemoglobin, it has a dark red-blue color which gives skin a characteristic bluish appearance. • Most cases arise as a result of peripheral vasoconstriction – result is reduced blood flow, which allows hemoglobin to give up more of its oxygen to tissues- peripheral cyanosis. • Best seen in nail beds • Due to cold environment, anxiety, etc. • Central cyanosis can be due to : – Abnormalities of the respiratory membrane – Mismatch between air flow and blood flow – Expressed as a ratio of change in ventilation (V) to perfusion (Q) : V/Q ratio • Pulmonary thromboembolus ---- reduced blood flow • Airway obstruction ---- reduced ventilation • In persons with dark skin can be seen in the whites of the eyes and mucous membranes. • Lack of cyanosis does not mean oxygenation is normal!! • In adults not evident until severe hypoxemia is present • Clinically observable when reduced hemoglobin levels reach 5 g/ dl. • Severe anemia and carbon monoxide poisoning give inadequate oxygenation of tissues without cyanosis • Individuals with polycythemia may have cyanosis when oxygenation is adequate. 4- Pain • Originates in pleurae, airways or chest wall • Inflammation of the parietal pleura causes sharp or stabbing pain when pleura stretches during inspiration – Usually localized to an area of the chest wall, where a pleural friction rub can be heard – Laughing or coughing makes pain worse – Common with pulmonary infarction due to embolism • Inflammation of trachea or bronchi produce a central chest pain that is pronounced after coughing – Must be differentiated from cardiac pain • High blood pressure in the pulmonary circulation can cause pain during exercise that often mistaken for cardiac pain (angina pectoris). 5- Clubbing • The selective bulbous enlargement of the end of a digit (finger or toe). • Usually painless • Commonly associated with diseases that cause decreased oxygenation – Lung cancer – Cystic fibrosis – Lung abscess – Congenital heart disease Infectious Diseases of The Lungs Introduction: • Daily 10,000 liters of air - filtered..! • Pneumonia: Inflammation of lung. • Respiratory tract infections – commonest in medical practice. • Enormous morbidity & mortality. Etiology: • Decreased general resistance • Virulent infection - Lobar pneumonia • Clearing mechanism – Decreased Cough Reflex – Injury of the cilia and mucosa – Low alveolar defense – Pulmonary edema or congestion – Obstructions – Retention of secretions Types: • • • • Viral Bacterial Mycoplasmal Fungal Patterns of infections: • Airway - Bronchitis, Bronchiectasis • Parenchyma – Pneumonia • Bronchopneumonia • Lobar pneumonia – Lung abscess – Tuberculosis Pneumonia • Pathology: – Alveolar • Bronchopneumonia (Streptococcus pneumoniae, Haemophilus influenza, Staphylococcus aureus) • Lobar (Streptococcus pneumoniae) – Interstitial (Influenza virus, Mycoplasma pneumoniae) • Pathogenesis – Inhalation of air droplets – Aspiration of infected secretions or objects – Hematogenous spread Bronchopneumonia • Suppurative inflammation of lung tissue caused by Staph, Strep, Pneumo & H. influenza • Patchy consolidation – not limited to lobes. • Usually bilateral • Lower lobes common, but can occur anywhere • Complications: – Abscess – Empyema – Dissemination Bronchopneumonia Bronchopneumonia Bronchopneumonia Bronchopneumonia: Bronchopneumonia Lobar Pneumonia: • Fibrinosuppurative consolidation – whole lobe • Rare due to antibiotic treatment. • ~95% - Strep pneumoniae • The course runs in four stages: – Congestion. – Red Hepatization. – Gray Hepatizaiton. – Resolution. Lobar pneumonia: whole lobe(s) involved Fixed specimen, grey hepatization Lobar pneumonia Lobar Pneumonia: Lobar Pneumonia – Gray hep… Lung Abscess: • Focal suppuration with necrosis of lung tissue • Organisms commonly cultured: – – – – – Staphylococci Streptococci Gram-negative Anaerobes Frequent mixed infections • Mechanism: – Aspiration – Post pneumonic – Septic embolism – Neoplasms • Productive Cough, fever. • Clubbing • Complications: Systemic spread, septicemia. Lung Abscess: Abscess formation Bronchopneumonia - Abscess formation Lung Abscess: Pulmonary tuberculosis • Caused by Mycobacterium tuberculosis. • Transmitted through inhalation of infected droplets • Primary – Single granuloma within parenchyma and hilar lymph nodes (Ghon complex). • Infection does not progress (most common). • Progressive primary pneumonia • Miliary dissemination (blood stream). Ghon complex Pulmonary tuberculosis • Secondary – Infection (mostly through reactivation) in a previously sensitized individual. – Pathology • Cavitary fibrocaseous lesions • Bronchopneumonia • Miliary TB Fibrocaseous Granuloma Miliary TB Opportunistic pneumonias • Infections that affect immunosuppressed patients • Associated disorders: – AIDS – Iatrogenic • Cancer patients • Transplant recipients Usual interstitial pneumonia / idiopathic pulmonary fibrosis • Progressive fibrosing disorder of unknown cause • Adults 30 to 50 years old • Respiratory and heart failure (cor pulmonale) ~ 5 y