CRL Quiz 2 2003

1

Which one or more of the following statements regarding drugs affecting the heart rate is/are correct?


  Increases in heart rate caused by stimulation of the cardiac sympathetic nerves are reduced by α-adrenoceptor antagonists.

  Decreases in heart rate caused by stimulation of cardiac parasympathetic nerves are reduced by muscarinic receptor antagonists.

  Atropine has little effect on resting heart rate.

  Propranolol is useful in the treatment of stress-induced tachycardia. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


A is incorrect. Stimulation of cardiac sympathetic nerves causes an increase in heart rate due to the stimulation of β-adrenoceptors by noradrenaline. B is correct. Acetylcholine released from parasympathetic nerves acts on muscarinic receptors to decrease heart rate. C is incorrect. Atropine, a muscarinic receptor antagonist, causes marked increases in resting heart rate. At rest there is significant tonic activity of the cardiac parasympathetic nerves to decrease heart rate. Antagonism of muscarinic receptors will prevent that effect resulting in an increase in heart rate. D is correct. Stress-induced tachycardias are associated with an increase in sympathetic nervous activity resulting in increased automaticity in the cardiac conduction system and in cardiac myocytes. Propranolol, a b-adrenoceptor antagonist, reduces that action of the sympathetic nerves.

2

Which one or more of the following statements regarding drugs affecting haemostasis is/are 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. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


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. D is correct. 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.

3

Which one of the following statements regarding a patient with uncontrolled asthma is correct?


  The TLCO is likely to be reduced.

  The peak flow is always reduced.

  The vital capacity is usually reduced.

  The forced expiratory ratio (ie FEV1/FVC) would be expected to be reduced.

  A change in FEV1 after inhaling salbutamol is unlikely.


In the asthma question, the first choice is wrong as TLCO is usually not affected by asthma, although sometimes it is elevated because of increased lung volume with hyperinflation. Peak flow will be reduced at times, but the important point is that peak flows are variable, so sometimes that will be down and not at other times. The VC will be normal, although in chronic severe asthma it can sometimes be reduced because of early gas trapping. The FER will be reduced indicating airflow obstruction. There would be expected to be an increase following inhaled bronchodilator, and even though this does not always happen it is wrong to say that it is unusual.

4

An elderly patient with Chronic Obstructive Pulmonary disease (COPD ) presents with worsening dyspnoea and the PaO2 is found to be 55 mmHg, the PCO2 to be 60 mmHg and the pH to be 7.31 while breathing room air. Which one of the following statements is correct?


  This represents chronic respiratory failure because COPD is a chronic disease.

  These are normal blood gases for an elderly patient.

  Administering supplemental oxygen will always reverse hypercapnia.

  The forced expiratory ratio (ie FEV1,/FVC) would be expected to be reduced.

  A change in FEV1 after inhaled salbutamol would be unlikely.


In the COPD question, the fact that the pH is low indicates an acute respiratory failure. If it was chronic the pH would be normal because of metabolic compensation with a raised HCO3. These blood gases are clearly abnormal, even for an elderly patient. Administering oxygen may help the hypoxaemia, but will not help the hypercapnia, and in fact may worsen it if too much oxygen is given too quickly. When using NIV, the aim is to return the pH to normal, not the PCO2. This is because some patients will have an acute worsening of the respiratory failure on top of a chronic compensated respiratory acidosis. Their usual PCO2 might be high. If it is brought down to normal, then the pH will be high, i.e. a metabloic alkalosis because of the compensatory chronic rise in HCO3 - and this can be dangerous.

5

Which one or more of the following statements regarding the development of pneumonia is/are correct?


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

  Pneumonia is more common 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. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


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.

6

Which one or more of the following statements concerning pulmonary oedema is/are 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. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


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 mls per hour. Lung compliance is reduced and this increases the elastic work of breathing.

7

Which one or more of the following statements regarding acute lung injury is/are correct?


  Acute lung injury may be caused by either intra- or extra- thoracic events.

  Acute lung injury is responsive to treatment with non-steroidal anti-inflammatory drugs.

  Acute lung injury may cause fibrosis.

  Acute lung injury is repaired by proliferation of type I epithelial cells. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


A is correct there are a large number of precipitants including intra-thoracic (eg aspiration of gastric contents) and extra-thoracic (eg major trauma) injury. B is incorrect: non-steroidal anti-inflammatories are not efficacious and there is still controversy over the efficacy of steroids (glucocorticoids). C is correct: Fibrosis may follow recovery from acute lung injury, especially if mechanical ventilation and/or hyperoxia were required. The alternate form of repair involves re-epithelialisation and is more likely following milder forms of injury in which the basement membrane of the epithelium is left intact. D is incorrect: Type II epithelial cells proliferate and then differentiate to type I epithelium.

8

Which one or more of the following statements regarding airway mucus is/are 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. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


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 B2-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. D is correct: 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.

9

Which one or more of the following statements regarding haemostasis is/are correct?


  Haemostasis is the arrest of bleeding from injured vessels

  Haemostasis is the process by which platelets are produced

  Thrombin catalyses the production of fibrin

  Thrombin is produced and released from damaged endothelium Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct

10

Which one or more of the following statements regarding the cardiac action potential of a ventricular myocyte is/are correct?


  The rapid upstroke is the result of sodium influx.

  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. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


A is correct: 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 and, therefore, prevent tetany.

11

Which one ore more of the following statements regarding cardiac myocyte contraction is/are correct?


  Contraction is activated by a rise in cell potassium concentration.

  Potassium is stored in the sarcoplasmic reticulum for release during contraction.

  Increased potassium causes the interaction between myosin and actin.

  Drugs such as digoxin reduce intracellular potassium concentration. Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


A is incorrect: Contraction is activated by a rise in cell calcium. B is incorrect: Calcium is stored in the sarcoplasmic reticulum for release during contraction. C is incorrect: Increased calcium causes the interaction between myosin and actin D is correct: Digoxin inhibits the NaK-ATPase pump and causes an decrease in intracellular [K], but this is not the reason that contractility increases.

12

Which one or more of the following conditions are true in relation to the profile of airflow through the trachea is/are correct?


  Airflow is turbulent

  Airflow is dependant on gas viscosity

  Airflow is dependant on gas density

  Airflow is laminar Answer 1 if only A, B and C are correct 2 if only A and C are correct 3 if only B and D are correct 4 if only D is correct 5 if all are correct


In large proximal airways, cross-sectional area is small, gas velocity high and turbulent flow conditions apply. Flow is proportional to the square root of pressure (relatively inefficient compared with laminar flow conditions) and density but not viscosity dependant. In the peripheral, small airways, airflow is laminar, directly related to driving pressure and dependant on gas viscosity – see Poiseuille’s equation.

13

The human B cell (B lymphocyte) humoral component of specific (adaptive) immune responses has been successfully exploited for which one of the following medically useful outcomes?


  Prevention of lung transplantation rejection.

  Vaccination against some respiratory pathogens.

  Suppression of TH1 biased responses in asthma.

  Reversing lung pathology in COPD.

  Reversing airway smooth muscle hyperplasia in asthma.


Protective antibody formation in the humoral immune response underlies the usefulness of vaccines against some lung pathogens such as influenza

14

Neuraminase inhibitors are most effective against which one of the following pathogens or class of pathogens?


  Pseudomonas aeruginosa.

  Human Immunodeficiency Virus (HIV).

  Influenza.

  Mycobacteria.

  Respiratory Syncytial Virus (RSV).


Neuramindase inhibitors specifically suppress Influenza infections.

15

A genetic mutation leading to overproduction of which one of the following secreted factors would most likely be associated with increased chances of developing allergic asthma


  MHCII (Major Histocompatibility Complex class II).

  IL-4 (Interleukin 4).

  IL-12 (Interleukin 12).

  IL-18 (Interleukin 18).

  TNF alpha (Tumour necrosis factor alpha).


Interleukin 4 is a major determinate of TH2 biased immune response. Promoter polymorphism in the IL-4 gene have been associated with increased risk of asthma. MHCII is a surface molecule. IL-12 and 18 are associated with TH1 responses. THF alpha is an inflammatory mediator.