Pneumonia is an acute inflammation of the lung parenchyma caused by a microbial organism. ETIOLOGY
Normal defense mechanism, normally, the airway distal to the larynx is sterile becouse of protective defense mechanisms.these mechanisns include the following : filtration of air, warning and humadification of inspired air, epligotis closure over the trachea, cough reflex, mucociliary escalator mechanism, secretion of immunoglobulin A and alveolar macrophages
Factor predisposing to pneumonia.Pneumonia is more likely t o result when defense mechanism become incompetent or ar overwhelmed by the virulence or quantity of infectious agents.Decreased consciousness depresses the cough and epligottal reflexes, which may allow aspiration of oropharyngeal contents into the lungs. Tracheal intubation interferes with the normal cough reflex and the mucociliary escalator mechanism. It also bypasses the upper airways, in which filtration and humidification of air normally take place. The mucociliary mechanism is impaired by air pollution, cigarette smoking, viral upper respiratory infections (Urls), andnormal changes of aging. In cases of malnutrition, the function of lymphocytes and and polymorphonuclear (PMN) leukocites are altered. Diseases such as leukimia,alcoholism and dibetes mellitus are assotiated with an increased frequency og gram-negative bacili in the oropharynx.(gram negative bacili are not normal flora in the respiratory tract). Altered oropharyngeal flora can also occur secondary to antibiotic therapy given for an infection elsewhere in the body.The factors presdiposing to pneumonia are:
1. Aging
2. Air pollution
3. Altered consciousness:alcoholism,head injury,seizures,anesthesia, drug overdose, stroke
4. Altered oropharyngeal flora secondary to antibiotics
5. Bed rest and prolonged immobility
6. Chronic disseases: chronic lung disease, diabetes mellitus,heart disease,cancer, end-stage renal disease
7. Debiliting illness
8. Human immunodeficiancy virus (HIV) infection
9. Immunosupressive drugs (corticosteroids, ancer chemotherapy,immunosuprressive therapy after organ transplant)
10. Inhalation or apiration of noxious substances
11. Intestinal and gastric feeding via nasogatric or nasoinstestinal tubes
12. Malnutrition
13. Smoking
14. Tracheal intubation (endotraceal intubation,tacheostomy)
15. Upper respiratory tract infection
Acquistion of organism.organism that cause pneumonia reach the lung by three methods:
1. Aspiration from the naopharynx or oropharynx.many of the organism that cause pneumonia are normal inhabitans of the pharynx in healthy adults
2. Inhalation of microbes presentin the air.Examples include mycoplasma pneumoniae and fungal pneumonias
3. Hematogenous spread from a primary infection elsewhere in the body. An example is staphylococcus aureus.
Types of pneumonia
Pneumonia can be couse by bacteria,viruses,mycoplasma fungi,parasites and chemicals.Althought pneumonia can be classified according to the causative organism, a clinically effective way is to classify pneumonia as comunity-acquired or hopspital-acquired pneumonia.classifying pneumonia is important becouse of differences in the likely causative organism and the selection of appropriate antibiotics.
Organisms associated with pneumonia
Community-acquired pneumonia
· Streptococcus pneumoniae
· Mycoplasma pneumoniae
· Haemophilus influenzae
· Respiratory virusses
· Chlamydia pneumophila
· Oral anaerobes
· Moraxella catarrhalis
· Staphylococcus auereus
· Nocardia
· Enteric aerobic gram-negative bacteria (e.g klebsiella)
· Fungi
· Mycobacterium tuberculosis
Hospital-acquired pneumonia
· Pseudomonas aeruginosa
· Enterobacter
· Escherichia coli
· Proteus
· Klebsiella
· Straphylococcus aureus
· Sterptococcus pneumonia
· Oral anaerobes
Community acquired pneumonia (CAP) is defined as a lower respiratory tract infection of the lung parenchyma with onset in the community or during the first 2 days of hospitalization.Smoking is an inportant risk factor. The causative organism is identified in CAP include S.pneumoniae (35%). H.influenza (10%) and atypical organism (e.g. legionella,mycoplasma,chlamydia viruses)
Once the patients is diagnosed with CAP, there are three step approach is recomended in initiating therapy
1. Assesment of the ability to treat the patient at home (e.g evaluate comorbidities,hemodynamic stability)
2. Calculation of the pneumonia PORT (pneumonia patient outcomes research team) severity index (PSI) with recomendations for home care and clinical judgment. This scale, produced by the agency for healthcare research and quality (AHRQ) is based on multiple factors and the score indicates the patients risk class
3. Clinician judgment in the final decision to treat, either as an outpatient in the hospital.
Hospital-acquired,ventilator-associated, and health care-associated pneumonia.]
Hospital-acquired pneumonia(HAP) is pneumonia occuring 48 hours or longer after hospital admission and not incubating at the time hospitalization.ventilator associated pneumonia (VAP) refers to pneumonia that occurs more than 48 to 72 hours after endotracheal intubation.Health care-associated pneumonia (HCAP) includes any patient with a new onset pneumonia who
1. Was hospitalized in an acute care hospital for 2 or more days within 90 days of the infection.
2. Resided in a long-term care facility
3. Received recent intravenous antibiotics therapy,chemotherapy,or wound care within the past 30 days of the current infection.
4. Attended a hospital or hemodialysis clinic.
Fungal pneumonia : Fungi may also be a cause of pneumonia
Aspiration pneumonia : refers to the sequelae occuring from abnormal entry of secretions or substances in to the lower airway. It usually follows aspiration of material from the mouth or stomach in to the tracea and subsequently the lungs. The person who has aspiration pneumonia usually has a history of loss of conciousness, the gag and cough reflexes are depressed , and aspiration is more likely to occur.Another risk factor is tube feedings. The dependent portions of the lung are most often affected, primarily the superior segments of the lower lobes and posterior segments of the upper lobes, which are dependent in the supine position.
Opportunisitic pneumonia.certain patients with altered immune response are highly susceptible to respiratory infections.individuals considered at risk include:
1. Those who have severe protein-calorie malnutrition
2. Those who have immune deficiencies
3. Those who have received transplants and been treated with immunosupressive drugs
4. Patient who are being treated with radiation therapy,cheotherapy drugs, and corticosteroids.
Pneumocytis jiroveci is an ooportunistic pathogen, this fungus rarely causes pneumonia in the healthy individual.pneumocystis jiroveci pneumonia (PCP) has been identified as the most common acquired immunodeficiency syndrome (AIDS).
Clinical manisfestations are insidious and include fever,tachypnea,tachcardia,dyspnea,nonproductive cough and hypoxemia.
PATHOPHYSIOLOGY
Pneumococcal pneumonia is the most common cause of bacterial pneumonia and is caused by the streptococcus pneumoniae organism.S.pneumoniae, also called pneumococcus can infect the upper respiratory tract, the blood and the nervous system. The organism is generally found in the nose and throat.When it invades the lung,pneumonia can occur.
The pathophysiology related to this type of pneumonia, there are four characteristic stages of the disease process:
1. Congestion, after the pneumococcus organism reach the alveoli, there is an outpouring of fluid in to the alveoli. The organisms multiply in the serous fluid, and the infection is spread.The pneumococci damage the host by their overwhelming growth and by interfering with lung function.
2. Red hepatization. There is massive dilation of the capillaries, and alveoli are filled with organisms,neutrophils, red blood cells (RBCs) and fibrin. The lung appears red and granular, similar to the liver, whic is why the process is called hepatization
3. Gray hepatization.Blood flow decreases, and leukocytes and fibrin consolidate in the affected part of the lung
4. Resolution, complete resolution and healing occur if there are no complications. The exudatw becomes lysed and is processed by the macropages. The normal lung tissue is restored, and the persons gas exchange ability return to normal.
CLINICAL MANISFESTATION
The symptoms of
