CRL Quiz 1 2009

1

Which one of the following statements regarding the blood vessels is correct?


  The blood flow velocity is slowest in the large veins.

  Small arteries are important determinants of total peripheral resistance.

  The lowest intravascular hydrostatic pressures are in the capillaries.

  The large veins act as diastolic pumps.

  The large arteries function as reservoirs for blood.


The major site of resistance in the circulation is at the level of the small arteries. The velocity of blood is slowest in capillaries, the lowest intravascular pressures are in the large veins, the large arteries act as diastolic pumps and the large veins function as reservoirs for blood.

2

Which one of the following statements regarding the normal heart is NOT CORRECT?


  The atrio-ventricular valves are closed during diastole.

  If the mitral valve is open, then the aortic valve must be closed.

  If the aortic valve is open, then the mitral valve must be closed.

  If the aortic valve is closed, then the mitral valve can be closed.

  The ventricular pressure during diastole depends on the compliance of the ventricle.


The atrio-ventricular valves need to be open during diastole so that the ventricles can be filled with blood.

3

The descending thoracic aorta passes from thorax into the abdomen


  adjacent to the xiphisternum at the level of T6.

  through the central tendon of the diaphragm at the level of T8.

  through the muscular part of the diaphragm at the level of T10.

  between the crura of the diaphragm at the level of T12.


The aortic hiatus is posterior to the diaphragm between the crura at the level of T12. Movements of the diaphragm therefore do not affect aortic blood flow during respiration.

4

Fluid (eg. vomitus) aspirated in the supine position typically enters which one of the following bronchopulmonary segments?


  Apical segment of the upper lobe.

  Posterior segment of the upper lobe.

  Apical (superior) segment of the lower lobe.

  Posterior basal segment of the lower lobe.


The apical (superior) segmental bronchus is the first to branch posteriorly from the bronchial tree and hence, in the supine position, inhaled fluid enters under the influence of gravitational force.

5

Ventilation in a normal adult


  occurs via the upper airway, trachea and branching bronchial system which has a total volume of about 50 mls.

  involves activation of the inspiratory and expiratory muscles at rest.

  occurs because the pleural pressure is less than the transpulmonary pressure.

  results in a minute ventilation of about 15 L/min at rest.

  maintains arterial pH lower than venous pH.


A is incorrect - Normal anatomical dead space is about 150mls. B is incorrect - Expiration at rest is usually passive i.e. no activation of the expiratory muscle. D is incorrect - Minute ventilation at rest in an average adult is about 7 - 8 L/min. E is incorrect - Venous pH is more acidic.

6

A normal adult is wearing a very tight band around their thorax. This is likely to


  reduce total lung capacity (TLC).

  reduce frequency of breathing.

  reduce the compliance of the lungs.

  reduce the resistive work of breathing.

  reduce the sensation of breathing.


B - Likely to increase frequency. C - Likely compliance will be unchanged (but chest wall compliance will be increased by the effect of the band). D - No change. E - Likely to increase it.

7

Comparing the characteristics of the blood in the pulmonary arteries (PA blood) with that in the pulmonary veins at sea level. In PA blood there is


  less dissolved carbon dioxide.

  more carbamino compounds.

  less bicarbonate.

  more dissolved oxygen.

  fewer binding sites for oxygen.


A - More dissolved carbon dioxide. C - More bicarbonate. D - Less dissolved oxygen. E - More un-occupied binding site.

8

The supply of oxygen to the tissues


  is independent of PaO2.

  will be doubled by doubling the FiO2 (from 0.21 to 0.42 at sea level).

  will be unchanged by breathing 5% carbon monoxide.

  is less if the Hb-oxygen dissociation is shifted to the left (lower P50)

  increases if cardiac output increases.


A is incorrect - Blood oxygen content is very dependent on PaO2. B is incorrect - Not in a normal person. This might be true in someone with disease causing many low V/Q units. C is incorrect - CO will reduce the number of binding sites on Hb and will reduce blood oxygen content and hence supply of O2 to tissues (unless cardiac output increases). D is incorrect - if considered at the tissue level.

9

The major house dust mite allergens are also


  amylases.

  neurotoxins.

  cholinesterases.

  proteases.

  histocompatibility antigens.


The major allergens from HDM are proteases from the gastrointestinal tract used by the mite to digest human skin, their main food source.

10

When airway smooth muscle is intensely contracted the observed shift in a β2-adrenoceptor agonist concentration response curve would reveal


  enhanced breakdown of acetylcholine.

  induction of excessive prostaglandin E2 (PGE2).

  gain of potency but loss of efficacy.

  reduced efficacy.

  Enhanced rate of relaxation and enhanced efficacy.


Functional antagonism of β2-adrenoceptors causes loss of potency (right shift in curve) and loss of efficacy (reduced response).

11

Which one of the following features is not a characteristic of acute lung injury?


  Pulmonary oedema.

  Increased respiratory work

  Ventilation/perfusion mismatch.

  Increased lung compliance.

  Hypoxemia.


In acute lung injury impairment of surfactant production, increased capillary hydrostatic pressure and breaches of the endothelial and epithelial barriers act together to cause pulmonary oedema. The oedema and reduced surfactant levels leads to reduced compliance, which increases the work of breathing. Areas of oedematous lung are under ventilated but may be normally perfused, whereas well ventilated regions of lung may be under perfused as a result of capillary occlusion by microthrombi or stiffened neutrophils or by upstream spasm of muscular arteries responding to hypoxia. This ventilation/perfusion mismatch leads to hypoxemia.

12

Which one of the following is NOT an effect of β2-adrenoceptor agonists?


  Airway dilatation.

  Skeletal muscle tremor.

  Tachycardia.

  Reduced bronchial swelling.

  Tolerance.


β2 adrenoceptor agonists cause airway dilatation by a relaxant action on airway smooth muscle. Chronic use of long-acting β2 adrenoceptor or regular use of short-acting β2 adrenoceptor agonists leads to tolerance. The most prominent adverse effects of β2 adrenoceptor agonists are fine tremor of skeletal muscle and tachycardia, each effect being a result of systemic actions. Inflammation that results in mucus production and bronchial wall swelling due to oedema is NOT diminished by β2 adrenoceptor agonists.

13

Which one of the following statements regarding mucus is NOT CORRECT?


  Mucus contains anti-oxidants.

  Mucus is secreted by goblet cells.

  Mucus is removed by the action of cilia.

  Mucus production is increased in asthma.

  Mucus production is reduced in COPD.


Mucus is a complex fluid that contains a number of chemical anti-oxidants. In the more proximal airways mucus is produced by both goblet cells and mucus glands; in the more distal airways mucus is produced exclusively by goblet cells. The mucus is removed by the unidirectional co-ordinated beating of cilia. In asthma and in COPD, mucus production is increased, as there are greater numbers of goblet cells and their activity is increased by the pro-inflammatory milieu.

14

The routine chest radiograph is optimally performed as an erect PA inspiratory examination in order to:


  magnify the cardiac contour so that it is more easily seen.

  allow fluid to adopt a level in the bases.

  cause the scapulae to be displaced away from the lung fields.

  cause the pulmonary arteries to distend thus becoming more visible.

  make the examination more comfortable for the patient.


The scapulae are displaced away from the lung fields by asking the patient to "hug" the film cassette in the PA position - a procedure not readily performed in the AP erect or supine positions. This is done to avoid superimposition of the bony scapulae on the lung fields. A is incorrect: the PA chest radiograph is designed to magnify the cardiac contour as little as possible in order to avoid edge blurring. B is incorrect: fluid does not normally adopt a level in the chest rather a "meniscus". D is incorrect: basal pulmonary veins distend in the erect position but pulmonary arterial calibre is not generally influenced by gravity. E is incorrect: the erect PA chest radiograph performed whilst hugging the cassette is not particularly comfortable nor is comfort per se the overriding parameter that determines the appropriate patient position for a radiograph rather the position chosen is one that produces the best quality or most diagnostic image.

15

Which one of the following statements concerning diffuse alveolar damage (DAD) is correct?


  Sepsis and gastric aspiration are common causes of DAD.

  Left ventricular failure is a common cause of DAD.

  Type 1 pneumocytes proliferate in response to DAD.

  A hyaline membrane accumulates within the alveolar wall in DAD.

  DAD is associated with reduced permeability of alveolar capillaries.


Sepsis and gastric aspiration are common causes of DAD. B is incorrect: Left ventricular failure is a common cause of pulmonary congestion and oedema, but not DAD. C is incorrect: Type 2 pneumocytes, not type 1 proliferate in response to DAD. D is incorrect: A hyaline membrane does not form within (i.e. inside) the alveolar wall, but rather on the surface and within the alveolar space since it forms from the necrotic debris and fibrin, etc. E is incorrect: DAD is associated with increased, rather than reduced permeability of alveolar capillaries.