RESPIRATORY path very important [anna].pptx

Respiratory system

1. RESPIRATORY patholog y . Congenital anomalies. Pulmonary hypoplasia – incomplete /under-development of the lungs[ one may be more affected than the other] resulting in decreased weight, volume and acini for body weight and gestational age. this is as a result of abnormalities that compressor impede normal lung expansion in utero e.g. diaphragmatic hernia and oligohydramnios. Severe neonatal hypoplasia is fatal in the early neonatal period . Note: In oligohydramnios-because of the low levels of amniotic-fluid, there is disruption in vascular endothelial growth factor signaling [VEGF] - important for pulmonary angiogenesis. There is also production of FIBROBLAST GROWTH FACTORS [FGFs],which alter lung branching morphogenesis and lead to abnormal lung development .additionally there is alteration in the thyroid hormone levels –impairing lung development.

2. Foregut cysts - arise from abnormal detachments from primitive foregut and are usually located in the hilum or middle mediastinum. these cysts are classified as bronchogenic [most common], esophageal and enteric depending of the wall structure. In this case, these cysts [bronchogenic] may compress/ obstruct the airways causing distress , coughing, and difficulty in breathing. sometimes they may communicate with the tracheobronchial tree and become infected. Note: bronchogenic cysts sometimes produce abnormal /low VEGF and FGFS as well as Wnt/beta catenin, which can impair lung development. These cysts can disrupt normal interaction between epithelial and mesenchymal cells, essential for lung development The following images show [to the left]: an x-ray image of a neonate with pulmonary hypoplasia and, [to the right]: bronchogenic cysts. Congenital anomalies count…..

3. Congenital anomalies continued…… Pulmonary sequestration – refers to lung tissue[segment/lobe] that [ i ]lacks any connection to the airway system and [ii]has blood supply from the aorta and its branches instead of the pulmonary artery. EXTRALOBAR SEQUESTRATION ;are external to the lungs and occur an where in the thorax/mediastinum; they most prevalent amongst infants as mass lesions and often associated with other congenital anomalies INTERLOBAR SEQUESTRATIONS ; occur within the lung parenchyma ;they typically occur in older children as recurrent localized infection /bronchiectasis. Other less common congenital abnormalities include tracheal and bronchial anomalies (atresia, stenosis, tracheoesophageal fistula), vascular anomalies, congenital pulmonary airway malformation and congenital lobar over inflation (emphysema ). The following images depict types of sequestration;

4. ATELECTASIS (COLLAPSE) Atelectasis comes from a Greek word Ateles - meaning I mperfect , ektasis – Extension . Atelectasis refers either to incomplete expansion of the lungs ( neonatal atelectasis) or to the collapse of previously inflated lung, producing areas of relatively airless pulmonary parenchyma. Significant atelectasis reduces oxygenation and predisposes to infection . Types of Acquired atelectasis[mainly encountered in adults] are classified as the following : RESORPTION ATELECTASIS : stems from complete obstruction of an airway. obstruction of the airway prevents fresh air from entering the alveoli, the oxygen is gradually absorbed into the bloodstream thereby, reducing the partial pressure of oxygen in the alveoli. nitrogen is less soluble and is slowly washed-out of the alveoli, however, carbon dioxide and water apour replace the oxygen and nitrogen in the alveoli . Over time, air is resorbed from the dependent alveoli, which collapse. Since lung volume is diminished, the mediastinum shifts toward the atelectatic lung. Airway obstruction is most often caused by excessive secretions (e.g., mucus plugs) or exudates within smaller bronchi, as may occur

5. Atelectasis continued….. in bronchial asthma, chronic bronchitis, bronchiectasis, and postoperative states. Aspiration of foreign bodies and, rarely, fragments of bronchial tumors may also lead to airway obstruction and atelectasis. COMPRESSION ATELECTASIS results whenever significant volumes of fluid (effusions from cardiac failure or neoplasms, transudate, exudate or blood aneurysm rupture), tumor, or air (pneumothorax) accumulate within the pleural cavity. With compression atelectasis, the mediastinum shifts away from the affected lung. CONTRACTION ATELECTASIS occurs when focal or generalized pulmonary or pleural fibrosis prevents full lung expansion .

6. Pulmonary edema Pulmonary edema ( leakage of excessive interstitial fluid which accumulates in alveolar spaces ) can result from hemodynamic disturbances (HEMODYNAMIC OR CARDIOGENIC PULMONARY EDEMA ) or from direct INCREASES IN CAPILLARY PERMEABILITY , as a result OF MICROVASCULAR INJURY. PULMONARY EDEMA results from either increased hydrostatic pressure or increased capillary permeability (due to endothelial or alveolar wall injury). Regardless of cause, lungs become heavy and wet, with dependent fluid accumulation Two main types of pulmonary edema discussed below include hemodynamic edema and edema caused by microvascular injury . HEMODYNAMIC PULMONARY EDEMA Hemodynamic pulmonary edema is due to increased hydrostatic pressure, as occurs most commonly in left-sided congestive heart failure. Fluid accumulates initially in the basal regions of the lower lobes because hydrostatic pressure is greatest in these sites (dependent edema). Histologically, the alveolar capillaries are engorged, and an intra-alveolar transudate appears as finely granular pale pink material. Alveolar microhemorrhages and hemosiderin laden macrophages (“heart failure” cells) may be present.

7. Pulmonary edema cont … In long-standing pulmonary congestion (e.g., as seen in mitral stenosis), hemosiderin-laden macrophages are abundant, and fibrosis and thickening of the alveolar walls cause the soggy lungs to become firm and brown (brown induration). These changes not only impair normal respiratory function but also predispose to infection. EDEMA CAUSED BY MICROVASCULAR (ALVEOLAR) Injury Noncardiogenic pulmonary edema is due to injury to the alveolar septa . Primary injury to the vascular endothelium or damage to alveolar epithelial cells (with secondary microvascular injury) produces an inflammatory exudate that leaks into the interstitial space and, in more severe cases, into the alveoli. In most forms of pneumonia the edema remains localized and is overshadowed by the manifestations of infection. When diffuse, however, alveolar edema is an important contributor to a serious and often fatal condition, acute respiratory distress syndrome .

8.   Classification and Causes of Pulmonary Edema Hemodynamic Edema Increased hydrostatic pressure (increased pulmonary venous pressure) Left-sided heart failure (common) Volume overload Pulmonary vein obstruction Decreased oncotic pressure (less common) Hypoalbuminemia Nephrotic syndrome Liver disease Protein-losing enteropathies Lymphatic obstruction (rare) Edema Due to Alveolar Wall Injury (Microvascular or Epithelial Injury). Direct Injury Infections: bacterial pneumonia Inhaled gases: high concentration oxygen, smoke Liquid aspiration: gastric contents, near-drowning Radiation Indirect Injury Septicemia Blood transfusion related Burns Drugs and chemicals: chemotherapeutic agents (bleomycin), other medications  (methadone, amphotericin B), heroin, cocaine, kerosene, paraquat Shock, trauma Edema of Undetermined Origin High altitude Neurogenic (central nervous system trauma)