CRL Quiz 2 2005

1

Which one of the following statements regarding arterial haemostatic clot formation is NOT correct?


  Arterial haemostatic clot formation requires stabilisation of the platelet plug.

  Arterial haemostatic clot formation is enhanced and accelerated by the actions of thrombin.

  Arterial haemostatic clot formation requires Vitamin K.

  Arterial haemostatic clot formation can occur even if only platelets are present.

  Arterial haemostatic clot formation requires von Willebrands factor binding to subendothelium.


Platelets make an important contribution to thrombus formation in the arteries but fibrin formation is also critical.

2

Which one of the following statements regarding drugs affecting haemostasis is correct?


  The onset of activity of warfarin, an oral anticoagulant, is delayed because it is a prodrug that is only slowly converted to the active compound.

  Aspirin, by inhibiting fibrin formation, is useful in the treatment of venous thrombosis.

  Heparin prevents the synthesis of the vitamin K dependent clotting factors.

  Activation of plasminogen by alteplase will result in the degradation of fibrin.


Alteplase by promoting fibrin degradation is used to breakdown thrombi and emboli for example in the treatment of coronary thrombosis (acute myocardial infarction) and pulmonary embolism.
A is incorrect: Warfarin prevents the synthesis of the vitamin K dependent clotting factors. It has as slow onset of activity because the clotting factors synthesised before warfarin administration need to be degraded before the anticoagulant effect becomes apparent.
B is incorrect: Aspirin is a cyclooxygenase inhibitor which prevents thromboxane synthesis by platelets and therefore inhibits platelet aggregation. It is useful in the treatment and prevention of arterial thrombosis. It has no effect on fibrin formation.
C is incorrect: Heparin by enhancing the activity of antithrombin III results in the breakdown of active factors. Warfarin prevents the synthesis of the vitamin K dependent clotting factors.

3

Which one of the following statements related to electrical conduction of the heart is correct?


  ECG provides information about the contraction force of the heart.

  Normally, all ventricular myocytes contract at the same time.

  Normally, PR interval is between 0.18 and 0.24 secs.

  Parasympathetic (vagal) activity decreases heart rate.


The ECG is an indication of electrical events in the heart, but gives no information regarding the force of contraction. Contraction in the ventricle begins at the apex and moves towards the base to efficiently eject the blood. The normal PR interval is approximately 0.16 seconds. A PR interval in the range of 0.18 and 0.24 seconds is abnormal and indicates a delay in AV conduction.

4

Which one of the following statements is correct? An important role of innate immune system Pattern Recognition Receptor (PRRs) in adaptive immunity is thought to be:


  Triggering T cell apoptosis (programmed cell death).

  Binding and neutralising IgG antibodies on the surface of T cells.

  Shaping the adaptive immune response.

  Preventing dendritic cells from migrating to lymph nodes.

  Exerting a strong anti-inflammatory effect, especially in the lung.


Primary recognition of pathogen associated molecular patterns (PAMPS) by PRRs helps to control the nature of the subsequent immune response by altering co-stimulation molecule pattern on antigen presenting cells and triggering cytokine release. The innate immune system is thought to discriminate between classes of pathogens very early in an infection and thereby shape the immune response in a manner that is usually most appropriate to the infecting agent.

5

Woolcock described asthma as “the disease where the airways close too easily and too much”. In functional terms, the dose of inhaled methacholine plotted against FEV1 in severe asthma would appear, relative to healthy people, to:


  Move leftward and upward.

  Have a clear plateau, but at a higher concentration of methacholine.

  Be identical but accompanied by sensation of breathlessness.

  Be easily corrected with inhaled β2-adrenoceptor agonists.

  Lack a clear plateau and move to the right.


The airways of asthmatic patients show an increase in sensitivity and maximum response to methacholine which would lead to a shift of the dose-response curve to the left and upward in comparison to normal individuals. Note: I think E should actually read "... and move to the LEFT." FEV1 will fall at LOWER methacholine doses for severe asthmatics. This would be consistent with the methacholine/FEV1 graphs in both lectures 2.3 and 2.5.

6

Which one of the following statements about pulmonary oedema is NOT correct?


  Adjacent endothelial cells in capillaries become leaky by retracting from each other.

  Neutrophil migration is an important mechanism breaching the capillary endothelium integrity.

  Mediators such as platelet-activating factor act directly on the endothelial cells to cause increases in capillary leakiness.

  An increased capillary hydrostatic pressure may increase the rate of oedema formation.

  Surfactant reduces the likelihood of pulmonary oedema.

7

Which one of the following statements regarding the development of pneumonia is correct?


  Inhalation of airborne infectious particles is the route of entry for the common bacterial causes of pneumonia.

  Pneumonia is uncommon in an individual with impaired upper airway reflexes.

  Lobar pneumonia is due to different organisms from those that cause bronchopneumonia.

  Hypoxaemia occurs in pneumonia because of low V/Q units and shunt.


Bacterial pneumonia is usually due to aspiration of infected saliva. Inhalation of airborne particles is the mode of entry by viruses, tuberculosis, mycoplasma, chlamydiophilia and legionella. The distribution of pneumonia as either lobar or bronchopneumonia does not help identify the causative organism.

8

Which one of the following statements concerning pulmonary oedema is correct?


  A common cause is hypoproteinaemia.

  The lymphatics clear fluid from the alveolar spaces at a rate of 20 mls per minute.

  Lung compliance is increased and this increases the resistive work of breathing.

  Kerley B lines are a radiological sign of both cardiogenic and non cardiogenic pulmonary oedema.


Low capillary oncotic pressure is theoretically a cause of pulmonary oedema (according to Starlings Equation) but in practice this is not a common mechanism. The lymphatics drain fluid from the interstitial spaces and the rate is about 20 ml per hour. Lung compliance is reduced and this increases the elastic work of breathing.

9

Which one of the following statements regarding airway mucus is correct?


  The production of mucus is decreased in chronic obstructive airway disease.

  Excessive mucus production is prevented by β2-adrenoceptor agonists.

  The mucocilliary escalator is stimulated by chronic exposure to tobacco smoke.

  The flow of mucus is dependent on the relative amounts of the gel and sol phase.


Excessive gel phase will provide resistance to the beating cilia, excessive sol phase leads to uncoupling of the gel phase from the force generated by the cilia that sweeps the mucus towards the mouth. A is incorrect: Asthma, chronic obstructive pulmonary disease and cystic fibrosis are characterized by excessive production and/or poor clearance of mucus. B is incorrect: The β2-adrenoceptor agonists increase fluid secretion and can therefore increase the volume of the sol phase of mucus. C is incorrect: The mucocilliary escalator shows reduced activity in tobacco smokers due to direct inhibitory actions on cilia beat frequency, increased viscosity of mucus and replacement of ciliated epithelium by goblet cells.

10

Which one of the following statements regarding the cardiac action potential of a ventricular myocyte is NOT correct?


  The rapid upstroke is the result of sodium efflux.

  The plateau is the result of calcium influx.

  Repolarisation is the result of potassium efflux.

  The absolute refractory period is associated with closed sodium channels.


A is incorrect: Opening of Na channels allows Na influx and depolarizes the membrane. B is correct: Opening of Ca channels allows Ca influx. C is correct: Opening of slow K channels allows K efflux. D is correct: Closed Na channels prevent depolarization during the refractory period and, therefore, prevent tetany.

11

When treating respiratory failure, which one of the following is correct?


  The primary aim is to maintain the PaCO2 in the normal range.

  High concentrations of oxygen should not be given to patients with acute asthma attacks as hypercapnia may be made more severe.

  During a severe acute asthma attack, a normal PaCO2 value gives the treating doctor confidence that the treatment is successful.

  In an acute exacerbation of severe COPD with worsening hypercapnia, noninvasive positive pressure ventilation is often a useful treatment option.

  In a patient with pulmonary embolism, a low PaCO2 indicates that the patient is hyperventilating and requires the administration of a respiratory depressant.


When treating respiratory failure, one important variable is the PO2 (or oxygen saturation) which should be kept above 60 mmHg (SpO2 > 90 %) on the flat portion of the oxygen dissociation curve, so that any minor changes in alveolar PO2 do not have major effects on the oxygen content of the blood. The pH is the other important factor, and is more important than the PCO2, because patients with chronic hypercapnia may have a high HCO3 to compensate for the chronic respiratory acidosis. In this situation, if the PCO2 is brought into the normal range, the patient will be left with a metabolic alkalosis, as the HCO3 levels do not change quickly. Thus the goal should be to get the pH normal, so response 1 is incorrect. B is incorrect, as the principal of not giving high doses of oxygen immediately during an exacerbation applies to patients with COPD who may have chronic hypercapnia. In this situation, the oxygen may overcome hypoxic pulmonary vasoconstriction in some parts of the lung, leading to a worsening of V/Q mismatch, making the patient more hypoxaemic and hypercapnic. There is also another explanation, that the high flow oxygen will suppress hypoxic drive, and that these patients may not have hypercapnic drive, and so there will be worsening hypoventilation. In acute asthma, these factors do not have a role. It is the hypoxia that kills in acute asthma, so patients must receive adequate oxygen. This is even more important if the patient is getting large doses of beta agonists, as these can cause more pulmonary vasodilatation than bronchial dilatation, worsening V/Q mismatch, and so making the hypoxaemia worse. C is incorrect. Initially PCO2 falls during an acute asthma attack, and it will rise back into the normal range if the attack is being relieved. But if the attack is not being relieved, and the asthma is getting worse, the patient may develop ventilatory failure and the PCO2 will start to rise, back into the normal range, and then higher into hypercapnia. In a patient with an acute asthma attack, which is not getting better, a rising PCO2, even from low to normal, is an ominous sign that requires urgent intervention. D is correct as this treatment approach has been shown to be of benefit in several well conducted clinical studies. It is now standard treatment in this situation. A patient with acute pulmonary embolism may have increased ventilation due to hypoxaemia. This can lower PCO2 as CO2 moves across the alveolar-capillary membrane more easily than O2. However, the treatment is to give supplemental oxygen to reverse the hypoxaemia. A respiratory depressant will worsen the hypoxaemia and may kill the patient. Response E is thus incorrect.

12

Which one of the following statements regarding the pericardium is NOT correct?


  It is a fibroserous sac.

  It lies posterior to the body of the sternum.

  It lies anterior to thoracic vertebrae 1 to 3.

  It encloses the heart and roots of the great vessels.

13

Which one of the following statements regarding the ventricles of the heart is NOT correct?


  The muscular ridges of the wall of the ventricle are called trabeculae carnae

  The papillary muscles are attached at their base to the walls of the ventricles

  The fossa ovalis is visible on the interventricular septum

  The pulmonary artery arises from the right ventricle

14

Which one of the following statements best explains the increased likelihood of pneumonia in elderly people?


  They have more contact with children with respiratory viral infections.

  They are less likely to receive influenza vaccination.

  They have reduced exercise capacity and therefore have reduced clearance of bronchial secretions.

  The mouths of elderly people are often colonized by fungi.

  Upper airway reflexes, mucosal immunity and systemic immune responses are often reduced compared to younger people.

15

Which one of the following statements regarding sleep is correct?


  PCO2 levels in the blood are lower than during wakefulness.

  The upper airway muscles relax so there is reduced pharyngeal resistance.

  Chemoreceptors are no longer active.

  Breathing becomes very irregular especially in NREM sleep.

  Ventilation is less than in wakefulness.