Pa Tho Physiology Of Pneumonia

Pathophysiology of pneumonia The invading organism causes symptoms, in part, by provoking an overly exuberant immune response in the lungs. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in a less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The patient breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide. Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection

. Consolidation, a feature of bacterial pneumonias, occurs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris. Bacterial infections

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The alveoli fill with proteinaceous fluid, which triggers a brisk influx of RBCs and polymorphonuclear cells (red hepatization) followed by the deposition of fibrin and the degradation of inflammatory cells (gray hepatization).

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During resolution, intra-alveolar debris is ingested and removed by the alveolar macrophages. This consolidation leads to decreased air entry and dullness to percussion. Inflammation in the small airways leads to crackles. Wheezing is less common than in viral infections.

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The inflammation and pulmonary edema that result from these infections cause the lungs to become stiff and less distensible, thereby decreasing tidal volume. The patient must increase his or her respiratory rate to maintain adequate ventilation.

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Poorly ventilated areas of the lung may remain well perfused, resulting in ventilation/perfusion (V/Q) mismatch and hypoxemia. Tachypnea and hypoxia are common.

acteria Main article: Bacterial pneumonia The bacterium Streptococcus pneumoniae, a common cause of pneumonia, photographed through an electron microscope. Bacteria typically enter the lung when airborne droplets are inhaled, but can also reach the lung through the bloodstream when there is an infection in another part of the body. Many bacteria live in parts of the upper respiratory tract, such as the nose, mouth and sinuses, and can easily be inhaled into the alveoli. Once inside, bacteria may invade the spaces between cells and between alveoli through connecting pores. This invasion triggers the immune system to send neutrophils, a type of defensive white blood cell, to the lungs. The neutrophils engulf and kill the offending organisms, and also release cytokines, causing a general activation of the immune system. This leads to the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils, bacteria, and fluid from surrounding blood vessels fill the alveoli and interrupt normal oxygen transportation. Bacteria often travel from an infected lung into the bloodstream, causing serious or even fatal illness such as septic shock, with

low blood pressure and damage to multiple parts of the body including the brain, kidneys, and heart. Bacteria can also travel to the area between the lungs and the chest wall (the pleural cavity) causing a complication called an empyema. The most common causes of bacterial pneumonia are Streptococcus pneumoniae and "atypical" bacteria. Atypical bacteria are parasitic bacteria that live intracellular or do not have a cell wall. Moreover they cause generally less severe pneumonia, thus atypical symptoms, and respond to different antibiotics than other bacteria. The types of Gram-positive bacteria that cause pneumonia can be found in the nose or mouth of many healthy people. Streptococcus pneumoniae, often called "pneumococcus", is the most common bacterial cause of pneumonia in all age groups except newborn infants. Pneumococcus kills approximately one million children annually, mostly in developing countries.[11] Another important Gram-positive cause of pneumonia is Staphylococcus aureus, with Streptococcus agalactiae being an

important cause of pneumonia in newborn babies. Gram-negative bacteria cause pneumonia less frequently than gram-positive bacteria. Some of the gram-negative bacteria that cause pneumonia include Haemophilus influenzae, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Moraxella catarrhalis. These bacteria often live in the stomach or intestines and may enter the lungs if vomit is inhaled. "Atypical" bacteria which cause pneumonia include Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila.

Bacterial pneumonia Antibiotics are used to treat bacterial pneumonia. In contrast, antibiotics are not useful for viral pneumonia, although they sometimes are used to treat or prevent bacterial infections that can occur in lungs damaged by a viral pneumonia.[citation needed] The antibiotic choice depends on the nature of the pneumonia, the most common microorganisms causing pneumonia in the local geographic area, and the immune status and underlying health of the individual. Treatment for pneumonia should ideally be based on the causative microorganism and its known antibiotic sensitivity. However, a specific cause for pneumonia is identified in only 50% of people, even after extensive evaluation.[citation needed] Because treatment should generally not be delayed in any person with a serious pneumonia, empiric treatment is usually started well before laboratory reports are available. In the United Kingdom, amoxicillin and clarithromycin or erythromycin are the antibiotics selected for most patients with community-acquired pneumonia; patients allergic to penicillins are given erythromycin instead of amoxicillin.[21] In North America, where the "atypical" forms of community-acquired pneumonia are becoming more common, macrolides (such as azithromycin and clarithromycin), the fluoroquinolones, and doxycycline have displaced amoxicillin as first-line outpatient treatment for community-acquired pneumonia.[22] The duration of treatment has traditionally been seven to ten days, but there is increasing evidence that shorter courses (as short as three days) are sufficient.[23][24][25] Antibiotics for hospital-acquired pneumonia include third- and fourth-generation cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and vancomycin.[26] These antibiotics are usually given intravenously. Multiple antibiotics may be administered in combination in an attempt to treat all of the possible causative microorganisms. Antibiotic choices vary from hospital to hospital because of regional differences in the most likely microorganisms, and because of differences in the microorganisms' abilities to resist various antibiotic treatments. People who have difficulty breathing due to pneumonia may require extra oxygen. Extremely sick individuals may require intensive care, often including endotracheal intubation and artificial ventilation. Over the counter cough medicine has not been found to be helpful in pneumonia.[27]