What is the common cause of epiglottitis?
What is the benefit of reducing the haemoglobin's affinity for O2?
It means that the O2 is released more readily in the tissues that need it.
Describe the pneumonia caused by E. coli.
Gram -ve bacteria that usually infects chronically ill patients
- It is usually caused by aspiration so affects the lower lobes
- It has a poor prognosis associated with it.
How do the globin polypeptides prevent the haem groups from irreversibly binding?
They form salt-bridges between the polypeptides which hold the structure in the deoxygenated state
Which bacteria is the most common cause of pneumonia?
Describe Streptococcus pneumoniae and the presentation of the pneumonia it causes.
- It is a Gram +ve diplococci bacteria that normally resides asymptomatically in the nasopharynx of individuals
- It produces an abrupt onset pneumonia with a classical 'rust' coloured sputum
- It produces a lobar pneumonia which can progress and become very serious
What drugs increase the risk of developing pneumonia?
- Atropine --> decrease in mucociliary escalator
- Sedatives --> decrease cough reflex and epiglottic function
- Salicylates --> decrease phagocytosis.
Which components of the blood are involved in the carriage of CO2?
- Plasma --> 5%
- Carbaminos; CO2 binding to amino groups in haemoglobin --> 5%
- RBCs; carbonic acid --> 90%
What is the chloride shift?
The chloride shift, or Hamburger's phenomenon, is the process whereby the HCO3+ is exchanged for Cl- across the membrane of the RBC
Which patients are most likely to develop a fungal pneumonia such as Aspergillus or Cryptococcus?
- Those who are immunocompromised or receiving chemotherapy
- Often have many symptoms of bacterial pneumonia.
What is the empiric treatment for complicated/severe pneumonia
- IV Cefuroxime
Apart from co-operative oxygenation, what other factors affect the affinity of O2 binding in haemoglobin?
What are the polypeptide subunits found in adult haemoglobin?
2 α subunits2 β subunits
Describe Klebsiella pneumonia and when it is likely to occur.
Gram -ve bacteria that normally colonised the oropharynx
- They cough a 'red-currant jelly' sputum
- It is mainly caused by aspiration in alcoholics or nosocomially and affects the right lower lobe
- There is usually heamoptysis and very poor prognosis
What the are the functions of the chloride shift?
- It eliminates HCO3+ from the RBC which encourages more CO2 to diffuse into the RBC
- The chloride in the RBC promotes O2 dissociation from haemoglobin.
Which bacteria cause a 'typical' pneumonia?
- Streptococcus pneumoniae
- Haemophilus influenzae
- Staphylococcus aureus in IV drug users.
How does ARDS present?
- Central cyanosis
- Bilateral chest crackles.
What are the normal values of PO2 and PCO2 in venous blood?
PO2 --> 30-50mmHg
PCO2 --> 40-52mmHg
What is the Haldane effect?
The property of haemoglobin that means deoxygenation increases it ability to carry CO2, and conversely oxygenation of haemoglobin decreases the capacity of haemoglobin to carry CO2
What is the empiric treatment of uncomplicated pneumonia?
What shape curve does the oxyhaemoglobin dissociation curve posses?
A Sigmoid shaped curve
How does CO2 decrease the haemoglobin's affinity for O2?
- The CO2 reacts with the amino terminals of the polypeptide chains to produce carbamates
- These carbamates are able to take part in the salt-bridge formation, therefore helping to stabilise the tense form of haemoglobin
Describe Psudeomonas aeruginosa pneumonia.
Gram -ve bacteria that usually infects COPD, bronchiectasis and CF patients
- It has a gradual onset, and is never cleared from the patient
- Patients produce copious amount of 'pea-green' sputum.
Describe the pneumonia caused by Mycobacterium tuberculosis.
- It is seen in those with foreign travel history or immunocompromised
- It has a gradual onset with fever, chest pain, weight loss, dry cough with heamoptysis
- It causes cavitation, effusion or miliary spread throughout the lungs
- It usually affects the upper lobes of the lungs.
What parameters constitute the CURB65 score?
Urea --> >7mm/l
65 or over
Which bacteria cause 'atypical' pneumonia?
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Legionella pneumophilia
- Coxiella burnetti
- Chlamydia psittaci
How is O2 transported within the body?
In the RBCs bound to haemoglobin
What are the typical symptoms of pneumonia?
- Abrupt onset
- High fever
- Pleuritic pain
- Purulent sputum
- Focal consolidation
Describe the pneumonia caused by Legionella pneumophilia.
Intracelluar Gram -ve bacteria that needs a wet environment to survive --> Air con units etc
- They present with a dry cough, fever, myalgia, diarrhoea, rash, oliguria, ARF, rhabdomyolysis and HSM
- It has a 5-30% mortality rate associated with it, as it mainly affects the immunocompromised
What are the 4 D's of epiglottitis?
- Drawn facies
Describe Chalmydia psittacci pneumonia.
- Intracellular Chlamydia psittacci bacteria inhaled from birds
- Other symptoms include fever, myalgia, macular rash, splenomegaly, severe cough, dyspnoea and depression...
- It requires long treatment and affects the lower lobes but has only 1% mortality attached to it.
How does 2,3-BPG reduce the affinity for O2 in haemoglobin?
- The BPG is closely related to the salt bridges of the polypeptide chains and helps prevent their breakage
- The higher the levels of BPG the more stable the salt-bridges are and this decrease the affinity for O2
What is the function of the globin polypeptides in haemoglobin?
They prevent the haem groups from irreversibly binding oxygen
Describe the pneumonia caused by Haemophilus influenzae.
- It is a Gram -ve bacteria
- It is usually causes pneumonia in patients with pre-existing lung conditions such as COPD or bronchiectasis
- It can produce a lobar or a diffuse (bronchoform of pneumonia
What does Bohr's effect state?
Haemoglobin's binding affinity is inversely related to both acidity and the concentration of CO2
Which bacteria can cause pharyngitis?
- Group A Streptococci
- Corynebacterium diptheriae
Describe the pneumonia caused by Mycoplasma pneumoniae.
- It is commonly seen in closed populations such as nursing homes etc
- Other symptoms can include arthralgia, mylagia, myocarditis, meningitis, hepatitis, IHA, skin eruptions and D & V
Which bacteria are associated with HAP pneumonia?
- Staphylococcus aureus
- E. coli
- Psuedomonas aeruginosa
Also don't forget the 'typical' pathogens.
What in the haemoglobin molecule is responsible for the carriage of O2?
The Fe2+ in the centre of each haem group
What investigations should be performed for pneumonia?
- Sputum --> AFB, general culture, and Gram staining
- Urine --> Legionella antigen and urine output
- Blood --> cultures, WBC, urea and serology
According to the Bohr effect, which direction will the oxygen dissociation curve shift if there is a decrease in pH and an increase in PCO2?
The curve will shift to the right, therefore the haemoglobin has a reduced affinity for O2
How many molecules of O2 can 1 molecule of haemoglobin carry?
4 O2 molecules; 1 bound to each of the 4 subunits of haemoglobin.
What enzyme is responsible for the production of bicarbonate from the dissolved CO2 in RBCs?
What are the normal PO2 and PCO2 values in arterial blood?
PO2 -->11-13kPa or 75-100mmHg
PCO2 --> 4.7-6.0kPa or 35-45mmHg
What is co-operative oxygenation?
- Binding of O2 to a single haem group causes a conformational change in the molecule
- This breaks some of the salt-bridges between the globin subunits
- This makes it easier for the other haem groups in the molecule to bind to O2
- This process of salt-brigde breaking and O2 binding continues until every haem group has bound to O2
Describe the Staphylococcus aureus, the type of pneumonia it causes and when it causes pneumonia.
- It is a Gram +ve bacteria that usually causes pneumonia following a viral infection such as Influenza
- It can also be caused after bacreraemia such as endocarditis
- It causes lung tissue lysis which leads to cavitation and abscesses
Empyema and septicaemia are also common features.
What are the atypical symptoms of pneumonia?
- Gradual onset
- Dry cough
- Myalgia and other systemic symptoms
- Less focal chest signs
Describe the pneumonia caused by Pneumocystis pneumonia.
- Yeast-like fungus that is seen in the immunocompromised patients --> HIV!
- They have progressive SOB, dry cough, fever and weight loss
CXR findings are inconsistent and range from nothing to white out
- It has a poor prognosis as treatment is difficult.
What is ARDS