Pneumonia Flashcards
Describe the anatomy of the airway.
The trachea is a cartilaginous tube, which splits into the bronchi.
The bronchi split into the bronchioles.
At the end of the bronchioles are the alveolar sacs.
The alveolar sacs contain alveoli, which are surrounded by capillaries.
Explain, briefly, the mechanism of gas exchange.
The capillaries surrounding the alveoli contain deoxygenated blood.
The high partial pressure of oxygen forces its way into the red blood cells and bind to the haemoglobin.
The high partial pressure of carbon dioxide in the red blood cells allow it to be released into the alveoli and exhaled.
Explain how the lungs are split into lobes.
The right lung is split into the superior, middle and inferior lobe.
The left lung is split into the superior and inferior lobe.
How does the presence of pneumococcal pneumonia inhibit gas exchange.
The bacteria rapidly divide within the spaces of the alveoli.
This is recognised and stimulates an inflammatory response:
- There is release of vasoactive cytokines, which cause vasodilation and increased vascular permeability, leading to exudate and neutrophils entering the alveoli.
- The build-up of the material and pulmonary oedema within the alveoli causes a decrease in ability for gas exchange to occur.
Once the macrophages phagocytose the neutrophils that have undergone apoptosis, the infection resolves.
There is often a productive cough, producing purulent (pus) sputum due to the build up of dead neutrophils.
Describe the clinical features of pneumonia.
Tachypnoea - the defective gas exchange increases the breathing rate to compensate.
Tachycardia - the loss of exudate causes an increase in viscosity of the blood. This means that there is less oxygenated blood being perfused at the organs and so heart rate increases to prevent organ failure.
Fever and malaise - pyrogens and acute phase proteins are released. These are to increase the rate at which the immune system works and to denature some of the pathogens, and to induce rest in the person.
Cough - this is often a productive cough to remove some of the sputum from the lower respiratory tract.
Describe the difference in flora between the upper and lower respiratory tract.
The upper respiratory tract has a large number of organisms that exist within the normal flora.
The lower respiratory tract is almost a sterile environment.
Explain the barriers that prevent ingress of pathogens that cause pneumonia.
Physical barriers - mucociliary escalator is where the mucosal membranes of the tract produce mucous to trap the pathogens. The cilia then waft the mucous up towards the mouth where it can be swelled and digested by the stomach or for expulsion.
Physiological barriers - coughing pushes sputum out of the lower respiratory tract for expulsion from the body.
Biological barriers - the normal flora can produce antimicrobials, as well as acting as competitive inhibitors for space and nutrients, against pathogenic organisms.
Explain some factors that can damage the mucociliary escalator.
Cigarette smoke.
Diabetes.
Recent viral infection.
Excessive alcohol consumption.
Describe some non-specific humoral factors produced in the lungs.
IgA - opsonisation aids in phagocytosis.
Ingress of neutrophils and macrophages - these can phagocytose and destroy pathogens.
Complement proteins - these can act as chemokines, they can opsonise, or they can kill pathogens directly.
Describe the 3 classes of pneumonia.
Hospital acquired pneumonia - infection of the lung parenchyma acquired within a hospital setting.
Opportunistic pneumonia - infection of the lung parenchyma acquired when the immune system is weakened.
Community acquired pneumonia - infection of the lung parenchyma, which develops outside the hospital.
Explain the meaning of primary and secondary pneumonia.
Primary pneumonia = there are no predisposing factors. When a normally healthy person develops an infection of the lung parenchyma, directly.
Secondary pneumonia = when there are predisposing factors, such as chronic lung disease, diabetes mellitus, or malignancy, prior to the infection of the lung parenchyma.
What are the most frequent pathogens associated with pneumonia in those above and below the age of 2?
Those above the age of two = streptococcus pneumoniae, haemophilia influenza and staphylococcus aureus.
Those below the age of two = respiratory syncytial virus.
What is the gram stain for streptococcus pneumonia?
Gram positive cocci in pairs.
How can you diagnose pneumonia?
Culture sputum.
What is the treatment for pneumonia?
Amoxicillin if mild.
Doxycycline if severe.
