CRL Quiz 1 2010

1

Which one of the following statements regarding the blood vessels is NOT CORRECT?


  The blood flow velocity is slowest in the capillaries.

  Small arteries are important determinants of total peripheral resistance.

  The large veins act as blood reservoirs.

  Blood in the pulmonary artery is blue.

  The compliance of the arteries is greater than the veins.


E is incorrect: The arteries have collagen, elastin and thicker walls so that they are less compliant than veins. As a result, a volume of blood in veins will be at lower pressure than the same amount in arteries.

2

Which one of the following statements regarding the cardiovascular system is NOT CORRECT?


  Arterial blood in the systemic circulation is always red under normal circumstances.

  Venous blood in the pulmonary circulation is always red under normal circumstances.

  Mean arterial pressure depends on reflected pressure waves.

  The walls of the left ventricle are thicker than those of the right ventricle.

  There are periods in the cardiac cycle when both the mitral and aortic valves are closed.


C is incorrect: Reflected waves are important determinants of the pulse pressure rather than the mean arterial pressure. However, the reverse is true, as an increase in TPR that might cause an increase in MAP will increase the magnitude of the reflected waves. An increase in MAP will also stretch the large arteries and reduce their compliance. This will increase the speed of conduction of pressure waves. As a result the reflected wave returns earlier and add to the pulse pressure more, because its peak coincides with the systolic peak of the primary pressure wave generated by the heart. This also increases pulse pressure and is similar to what happens when aged and stiffen atherosclerotic large arteries lose their compliance.

3

The oesophageal hiatus in the diaphragm is


  through the central tendon.

  at the level of T10.

  unaffected in diameter by contraction of the diaphragm.

  the most anterior of the major hiatuses.


The oesophageal hiatus is through the muscular part of the diaphragm, posterior to the central tendon and the IVC hiatus, at the level of T10. It constricts with diaphragmatic contraction.

4

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


  Visceral pleura covering the lungs is supplied by the phrenic nerve.

  Parietal and visceral pleura are continuous around the hilar structures.

  The right lung typically has a horizontal fissure.

  The apex of each lung rises above the level of the clavicle.

  The medial surface of the left lung has deep impressions caused by adjacent arterial structures.


The visceral pleura covering the lungs shares the visceral nerve supply of the lungs. The phrenic nerve supplies the diaphragmatic and mediastinal pleura.

5

Which one of the following statements regarding normal lungs is correct?


  Pulmonary capillary pressures are the same as systemic capillary pressures.

  Work of breathing comprises about 15% of total energy expenditure at rest.

  The surface area of the alveolar-capillary (A-C) membrane is the main limitation to maximum exertion.

  Type 1 alveolar cells are the main structural cell of the A-C membrane.

  The A-C membrane can secrete oxygen.

6

Which one of the following statements regarding spirometry is correct?


  Normal values are affected by the patient's weight.

  FEV1 increases with increasing age.

  Spirometry is always abnormal in patients with asthma.

  The FEV1 is normal in restrictive lung disease.

  An FEV1/FVC ratio less than 0.7 indicates airflow obstruction.


A is incorrect: Normal values for spirometry are determined by age, gender, height and race, but not weight. B is incorrect: FEV1 declines with age in normal non-smoking people by about 15-20 ml per year. C is incorrect: The airflow obstruction in asthma is variable, so sometimes it may be normal and at other times abnormal. Thus one normal spirometry result does not exclude asthma. D is incorrect: In restrictive lung disease the size of the lungs is reduced so both FEV1 and FVC are reduced, but the FEV1/FVC ration is normal. E is correct: By definition airflow obstruction is when the FEV1/FVC ratio is reduced. The normal cut-off is about 0.7, although this does vary slightly with age, being a little lower in older people and a little higher in young adults.

7

A 30 year old painter falls off a ladder. He has severe chest pain and has increasing shortness of breath over the next hour. On a chest X-ray in hospital he has a collapsed lung with air in the pleural space. What occurs during inspiration that promotes this problem?


  Intra-alveolar pressure is greater than atmospheric pressure.

  Intra-alveolar pressure is less than atmospheric pressure.

  Intra-pleural pressure becomes less negative.

  Intra-pleural pressure becomes more negative.

  Contraction of the abdominal muscles.


The painter has a pneumothorax (air in the pleural space) as a result of trauma puncturing the lung surface. Air is 'sucked' into the intra - pleural space as a result of the negative pressure in the intra-pleural space, which becomes more negative during inspiration. Intra-alveolar pressure is less than atmospheric pressure during inspiration, but this does not cause the pneumothorax.

8

In the context of childhood asthma IL-4 is most closely associated with


  atopic predisposition.

  rhinoviral resistance.

  TH1 immunity.

  Treg over-activity.

  FEV1.

9

Glucocorticoids have therapeutic effects in asthma by


  increasing cyclic nucleotide levels.

  relaxing airway smooth muscle.

  blocking cysteinyl leukotriene receptors.

  reducing cytokine synthesis.

  reducing cytoplasmic calcium levels.


β2-adrenoceptor agonists and phosphodiesterase inhibitors can increase the concentrations of cyclic nucleotides, but glucocorticoids do not act on these pathways, nor do they have acute effects on airway smooth muscle (chronically, mediator levels will be decreased and muscle will be more relaxed as a consequence). Cys LT receptors are not blocked by glucocorticoids. Cytokine production is inhibited to a significant extent by glucocorticoids and is a major aspect of their therapeutic effect. There is no evidence for glucocorticoids regulating cytoplasmic calcium levels.

10

A patient presents for a routine pre-employment chest radiograph. Which one of the following statements is correct?


  The grey scale of the radiographic image is dependent on the patient's ability to suspend respiration.

  The arms are placed at the patient's side in order to maintain a fixed position.

  The X-ray tube will be located on the anterior aspect of the patient's anterior chest wall.

  The right cardiac border on the anterior view represents the right atrium.

  The horizontal fissure divides the right lung into middle and lower zones.


A is incorrect: Blurriness (motion artifact) of the image is affected by breathing. Grey scale is dependent on the electron density (X-ray attenuation) of the tissues being examined and the exposure factors used. B is incorrect: Shoulders are abducted and arms "hug" the X-ray cassette in order to move the scapulae away from being superimposed on the lung fields. C is incorrect: Pre-employment chest is performed as a PA (posterior to anterior) i.e. the X-ray tube is towards the back of the patient. D is correct. E is incorrect: horizontal fissure divides the lung into right upper and middle lobes. The zones of the anterior chest radiograph are divided arbitrarily into thirds (with no defined anatomical structure).

11

Which one of the following statements regarding carbon dioxide (CO2) transport from the tissues is correct?


  It is severely affected by anaemia.

  CO2 crosses the A-C (alveolar-capillary)membrane more readily than oxygen.

  CO2 is mainly transported dissolved in blood.

  Carbonic anhydrase speeds the conversion of CO2 to bicarbonate in plasma.

  Enhanced binding of CO2 to deoxy haemoglobin is the Bohr effect.

12

Which one of the following statements concerning the following arterial blood gas sample collected from a 20 year old male is correct? pH 7.28, PaO2 108, PaCO2 28, HCO3 15


  He must be breathing supplemental oxygen because the PaO2 is high.

  The primary abnormality is a respiratory alkalosis.

  The primary abnormality is a respiratory acidosis.

  He is likely to be suffering from a narcotic overdose.

  He might have diabetic keto-acidosis.


A is incorrect: The PaO2 could be high because of the hyperventilation rather than breathing supplemental oxygen. B is incorrect: The primary abnormality is a respiratory acidosis not alkalosis. C is incorrect: He has metabolic acidosis because his PaO2 is not raised. D is incorrect: one would expect hypoventilation and a respiratory acidosis.

13

Which one of the following is NOT associated with acute lung injury?


  Dyspnoea.

  Tachypnoea.

  Hypoxemia.

  Increased compliance.

  Decreased lung volumes.


Acute lung injury is accompanied by regional oedema that increases the work of breathing through reductions in compliance, due to loss of surfactant and the inflammatory exudate that forms fibrin in the airspaces. The oedema and other features of the injury such as hypoxic pulmonary vasoconstriction can lead to ventilation/perfusion mismatch resulting in a hypoxemia that is refractory to treatment with supplemental oxygen. Lung volumes are reduced by oedema and sensory receptors together with increased respiratory rate provide the sensation of difficulty in breathing.

14

Which one of the following statements about lung defense mechanisms is NOT CORRECT?


  Mucus is swept towards the glottis by direct contact of beating cilia.

  Particles of less than 5 micron in diameter settle by diffusion in the alveolar air spaces.

  Mucus contains peptide and enzymatic anti-microbials.

  Cilia beating frequency is decreased by exposure to tobacco smoke.

  Airway smooth muscle contraction is essential to prevent noxious gas reaching the alveolar membrane.


Mucus is moved towards the glottis by the action of the mucocilliary escalator achieved by coordinated unidirectional waves that direct the film of mucus towards the glottis. The mucus typically entraps particles in the 3- 10 micron range, with particles of 5 micron and less having the propensity to settle in the alveoli by diffusion. The cilia beat frequency may be reduced by a variety of environmental exposures, including air-pollution and tobacco smoke. Airway smooth muscle does not redirect or prevent ventilation due to presence of noxious gases - there could be no advantage of such a system: irritant effects of such exposures should evoke an avoidance response.

15

Which one of the following is the site of the main pacemaker driving respiratory rhythm?


  Pre-Botzinger complex.

  Retrotrapezoid nucleus.

  Pontine respiratory group.

  Apneustic centre.


The pre-Botzinger complex is the minimal slice preparation of the brainstem capable of producing a phasic respiratory rhythm and is thought to be the primary respiratory pacemaker.