Term
| What are the normal pO2 & pCO2 values in arterial/mixed venous blood? |
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Definition
Arterial blood - paO2 ~100mmHg, paCO2 ~40mmHg
Mixed venous blood – pvO2 ~35mmHg, pvCO2 ~45mmHg |
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Term
| Haemoglobin is made up of four subunits, what is each subunit made up of? |
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Definition
| 1 haem group with 1 Fe+ at the centre and 1 globin polypeptide surrounding the haem group, two of the 4 globins have alpha chain and the other 2 have beta chains. |
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Term
| What is the function of globins in haemoglobin? |
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Definition
| Prevent heamo groups irreversibly binding to oxygen by stopping the two haem groups coming too close together and 'sandwiching' the O2 molecule. |
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Term
| When deoxygenated, what holds Hb subunits together? |
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Definition
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Term
| O2 binding to a sub-unit has what impact on globin? |
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Definition
| Changes the conformational shape. |
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Term
| Salt bridge breaking makes further O2 binding more easy, but what makes salt bridge breakage more likely? |
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Definition
| Salt bridge breakage is more likely every time O2 binds to a sub-unit therefore O2 binding makes further O2 uptake more likely. |
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Term
| What shape would you expect an O2 dissociation curve to have and why? |
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Definition
Sigmoid shape due to;
1.Shallow curve at very low pO2 Hb entirely deoxygenated (very rare)
2. Steep curve at low pO2 (20-50mmHg), Hb readily gives up O2 at tissue due to salt bridge formation with dissociation and encouraging further dissociation.
3.Shallow curve at high pO2 (>75mmHg), Hb readily accepts O2 in lungs due to Hb saturation |
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Term
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Definition
| O2 curve shifts right with reduced Hb affinity for O2 due to increased [H+], increased [CO2] or increased temperature |
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Term
| What causes the bohr effect and how is it beneficial? |
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Definition
| Caused by a chloride shift and increased salt bridge formation. Beneficial as it means more O2 is readily released during excercise. |
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Term
| What effect does BiphosphoGlycerate(BPG)have on Hb and the O2 dissociation curve? |
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Definition
| Reduces affinity and shifts the curve to the right by resisting salt bridge breakage therefore decreases O2 binding. |
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Term
| How does BPG differ in foetal HB and why? |
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Definition
| BPG levels are decreased therefore Hb has a higher oxygen affinity meaning foetal Hb picks up O2 at low placental pO2 values |
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Term
| How much O2 is associated with Hb and how much dissolves in plasma? |
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Definition
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Term
| What are the 3 methods of CO2 carriage in the body? |
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Definition
| 5% plasma, 5% carbaminos and 90% carbonic acid in RBC's. |
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Term
| What is the Haldane effect? |
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Definition
| Increased CO2 carriage at low pO2 due to carbonic acid formation in deoxygenated Hb. |
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Term
| How does carbonic acid in RBC's cause a chloride shift? |
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Definition
| H2O + CO2 ↔ H2CO3 ↔ HCO3- + H+ , then HCO3- diffuses out of the RBC and Cl- diffuses into the RBC in exchange. |
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Term
| What is the benefit of the chloride shift? |
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Definition
| HCO3- elimination from RBC's allows for more CO2 dissolution and Cl- ions in RBC's lead to increased O2 dissociation. |
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Term
| What factors modify the lungs ability to transfer gases and therfore change the diffusing capacity of the lung (DL)? |
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Definition
| Rate of diffusion of gas across the alveoli and the rate of uptake/release of gas. |
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Term
| In what time does blood become saturated with O2 within the alveoli? |
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Definition
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Term
| At rest blood spends approx. 0.75seconds in the alveoli, how does this change with exercise and what is the clinical significance of this? |
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Definition
| During exercise blood may remain in the alveoli for as little as 0.25secs (due to increased HR), therfore progressive lung disease will affect people first during exercise. |
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Term
What causes variation in the VA/Q Ratio?
(VA/Q Ratio=Alveolar Ventil/Perfusion) |
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Definition
| Gravity, ventilation and perfusion greater at the base of the lungs. |
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Term
| What bacterial pathogen is the most common cause of pneumonia? |
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Definition
| Streptococcus Pneumoniae (60-75%), G+ |
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Term
| A patient presents with a sudden onset of fever, cough producing rusty coloured sputum, pleuritic pain and dyspnoea. Is this a medical emergency? |
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Definition
| Yes, streptococcus pneumoniae. Rapidly multiplying bacteria, sudden onset lobar pneumonia. |
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Term
| Haemophilus influenzae pneumonia is most common in which population? |
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Definition
| Patients with chronic lung conditions such as COPD or bronchiectasis. |
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Term
| What are common characteristics of Staph Aureus pneumonia? Which population would you expect to find it in? |
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Definition
Rusty coloured sputum, septicaemia, empyema and abscesses common.
Expected in IV drug users or children who have been ill recently. |
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Term
| How would you expect mycoplasma pneumoniae to present? |
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Definition
| Chest symptoms preceded by generalised symptoms for 1-5 days. Affects young adults in closed populations. |
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Term
| How severe is a diagnosis of legionella pneumoniae? |
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Definition
| Very, mortality 5-30%. Aquired by immunocompromised and institutional outbreaks. |
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Term
| What symptoms would you expect with Legionella? |
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Definition
| Dry cough, fever, rigors, myalgia, diarrhoea (50%), rash, oliguria, ARF, rhabdomyolysis and HSM. |
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Term
| What bacteria would you expect to cause an aspiration pneumonia? |
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Definition
| Anaerobic E. Coli, most common in patients with a poor gag reflex. |
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Term
| Would you expect a pneumonia caused by Pseudomonas Aerginosa to have a sudden or gradual onset? |
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Definition
| Slow onset, copious green sputum, most commonly presents in cystic fibrosis patients. |
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Term
| How would you differentiate between consolidation and effusion in the lungs on X-ray? |
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Definition
Consolidation appears fluffy and has no meniscus.
Effusion appears solid and has a meniscus present. |
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Term
| Which pneumonias would you expect to be hospital acquired? |
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Definition
| Staph. Aureus, Klebsiella, E.Coli and Pseudomonas aerginosa. |
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Term
| Pneumocystis is a fungal rare cause of pneumonia, who would you expect it present in? |
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Definition
| Immunocompromised, AIDS sufferers. |
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Term
| How would you identify a lobar pneumonia? |
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Definition
| Infection confined to one lobe, this lobe would be identified by structural border loss on X-ray eg. Diaphragm- lower lobe and Heart borders- right middle/left upper. |
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Term
| How would you identify a bronchial pneumonia on X-ray? |
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Definition
| Patches throughout the lungs rather than in one lobe. |
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Term
| What investigations would you carry out on a patient with pneumonia? |
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Definition
| Sputum sample, U&Es, FBC's, ECG, CXR and ABG's. |
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Term
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Definition
| A scoring system used to assess severity in combination with poor prognosis factors contributing to severe pneumonia. |
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Term
| Name contributing poor prognostic factors of pneumonia |
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Definition
| Co-existing disease (IHD, Ca, COPD, DM, CVA), albumin <35g/L, WCC <4/>20, multilobar involvement, hypoxia stats and positive blood culture. |
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Term
| What complications can result from pneumonia? |
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Definition
| Lung abscess, empyema, ARD, Bronchiectasis and Pulmonary emboli. |
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Term
| What is epyema? What in pneumonia causes it? How do you treat it? |
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Definition
| Pus within pleural cavity, typically caused by anaerobic bacteria from bacterial spread or rupture of an abscess. Requires prompt intercostal drain. |
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Term
| What is ARD? What does it cause? How do you treat it? |
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Definition
Acute respiratory distress.
Causes a build up of fluid in the alveoli, low BP and difficulty breathing.
ITU required with positiv end-expiratory pressure (PEEP). |
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