CRL Quiz 1 Professor Irving Revision

1

The main roles of the respiratory system are to add O2 and remove CO2 from pulmonary capillary blood.


  True

  False

2

PiO2 in the upper airway at sea level is about 150 mmHg.


  True

  False


Lower once it is humidified as it passes into the lower airway

3

PAO2 at sea level is always about 100 mmHg.


  True

  False


Depends on the level of ventilation

4

The oxygen content of blood in the pulmonary arteries is the same as that in the systemic arteries.


  True

  False


The pulmonary arteries contain systemic venous blood

5

The pH of pulmonary arterial blood is lower than the pH of pulmonary venous blood.


  True

  False

6

Atmospheric pressure declines linearly with increasing altitude and at 18,000 feet is about 380 mmHg.


  True

  False


First statement false, second statement true

7

Pressure increases linearly with increasing depth under water.!


  True

  False

8

At a depth of 10 meters at an altitude of 18,000 feet, the total pressure would be about 1140 mmHg.


  True

  False

9

Basal metabolic rate is about 250 ml/min O2 and 200 ml/min CO2 and hence the respiratory exchange ratio, R, is 1.2.


  True

  False


First 2 statements true but RER = CO2/O2 = 0.8

10

The metabolic rate, and hence oxygen consumption, increases with exercise, fever, inflammatory conditions and malignancy.


  True

  False

11

Ventilation is an energy requiring process and at rest is about 15% of the body’s energy consumption.


  True

  False


In normals is about 2-3% at rest

12

The work of breathing involves resistive forces due to stretching of the lungs and elastic forces due to the friction of airflow in the bronchi.


  True

  False


Other way round

13

At FRC the elastic recoil of the chest wall is balanced by the elastic recoil of the lungs and this explains the increase in FRC in pulmonary fibrosis.


  True

  False


Nasty question – first half true and logic for second statement is correct except that FRC in pulmonary fibrosis is decreased not increased

14

Tidal volume is about 500 ml in adults at rest and is composed of alveolar volume of about 350 ml and dead space of about 150 ml


  True

  False

15

During inspiration intrapleural pressure is more negative at the base of the lung compared to the lung apex.


  True

  False


Less negative due to gravitational effects

16

Airflow is laminar throughout the upper and lower airways.


  True

  False

17

Because a 80/20 helium/oxygen mixture is less dense than air it can be used in situations of severe airflow obstruction to reduce resistive forces.


  True

  False

18

Spirometry measures all the lung volumes including TLC, FRC and RV.


  True

  False

19

The hallmark of an obstructive defect is a reduction in FEV1 and the forced expiratory ratio.


  True

  False

20

Alveolar hypoventilation is characterised by an elevated PaO2.


  True

  False


Elevated PaCO2

21

Because the pulmonary circulation is at a lower pressure than the systemic circulation, the cardiac output from the right ventricle is lower than the left.


  True

  False

22

Pulmonary artery pressure increases markedly with exercise.


  True

  False

23

Pulsus paradoxus is a reversal of the normal swings in systolic pressure with respiration.


  True

  False

24

A reduction in regional oxygen concentration in the lungs causes dilation of the pulmonary arterioles to that area.


  True

  False

25

Gas exchange is most efficient when there is roughly a 1:1 ratio of ventilation and perfusion in all A/c units.


  True

  False

26

High V/Q units represent wasted ventilation and contribute to the physiologic dead-space.


  True

  False

27

Low V/Q units are a common cause of hypoxaemia.


  True

  False

28

Supplemental oxygen fully corrects the hypoxaemia caused by shunts


  True

  False

29

Diffusion impairment is a common cause of hypoxaemia at rest.


  True

  False

30

The alveolar – arterial gradient for oxygen is widened if there is inefficient gas exchange in the lungs.


  True

  False

31

Oxygen diffuses across the A-C membrane more rapidly than CO2


  True

  False

32

Oxygen transfer across the A-C membrane is perfusion limited meaning that the amount of blood available limits the total amount of O2 transferred rather than the diffusion capacity of the membrane.


  True

  False

33

O2 carriage in the blood is predominantly by hemoglobin and each Hb molecule can carry a maximum of 3 molecules of O2.


  True

  False


First statement true, second false

34

1 gm of fully saturated Hb carries 1.3 litres of O2.


  True

  False


mLs not litres

35

The O2 content of blood is influenced by PaO2, [Hb] and cardiac output.


  True

  False


Not by cardiac output

36

Unloading of O2 in the tissues is aided by increased H+ and CO2.


  True

  False

37

CO2 and CO bind to the same site on Hb as O2.


  True

  False


CO but not CO2

38

CO2 is transferred in blood as HCO3 and this is formed by carbonic anhydrase in the serum.


  True

  False


CA is in RBC

39

A respiratory acidosis is due to inadequate CO2 removal by the lungs.


  True

  False

40

The compensation for a metabolic acidosis is hyperventilation.


  True

  False

41

pH: 7.40, PaCO2: 40, HCO3: 25


  Respiratory alkalosis

  Respiratory acidosis

  Metabolic acidosis

  Metabolic alkalosis

  None of the above


These values are normal. Also, the explanations for these questions are my own - take with a grain of salt!

42

pH: 7.30, PaCO2: 60, HCO3: 27


  Acute respiratory acidosis

  Acute metabolic acidosis

  Compensated respiratory acidosis

  Compensated metabolic acidosis


Acidosis (low pH) with high PaCO2 indicates respiratory acidosis. HCO3 is slightly raised as expected when CO2 combines with H2O for form H+ and HCO3.

43

pH: 7.37, PaCO2: 60, HCO3: 33


  Acute respiratory acidosis

  Acute metabolic acidosis

  Compensated respiratory acidosis

  Compensated metabolic acidosis


pH is normal, but both PaCO2 and HCO3 are high, suggesting respiratory acidosis with renal compensation.

45

pH: 7.28, PaCO2: 30, HCO3: 16


  Acute respiratory acidosis

  Acute metabolic acidosis

  Compensated respiratory acidosis

  Compensated metabolic acidosis


Acidosis (low pH), but PaCO2 is low which rules out respiratory acidosis. Metabolic acidosis is usually caused by either addition of acid (other than CO2) or loss of bicarbonate - the latter may be the case here, or bicarbonate may be low due to buffering (to figure out which, you need to look at the ANION GAP [Na+K]-[Cl+HCO3], normal = HCO3 loss, > 15 = addition of a new acid).

46

pH: 7.50, PaCO2: 30, HCO3: 24


  Acute respiratory alkalosis

  Acute metabolic alkalosis

  Compensated respiratory alkalosis

  Compensated metabolic alkalosis


Alkalosis (high pH) due to respiratory causes (low CO2). As for Q2, normal HCO3 contraindicates compensation and metabolic causes.

47

pH: 7.43, PaCO2: 30, HCO3: 21


  Acute respiratory alkalosis

  Acute metabolic alkalosis

  Compensated respiratory alkalosis

  Compensated metabolic alkalosis


PaCO2 low (respiratory alkalosis) with normal pH and slightly lowered HCO3 indicating renal compensation.

48

pH: 7.50, PaCO2: 46, HCO3: 30


  Acute respiratory alkalosis

  Acute metabolic alkalosis

  Partially compensated respiratory alkalosis

  Partially compensated metabolic alkalosis


Alkalosis (high pH), but high PaCO2 both rules out a respiratory alkalosis and also indicates respiratory COMPENSATION for metabolic alkalosis. High HCO3 suggests that renal bicarbonate retention (or increased production) may be the cause. To know for sure, you need to look at the ANION GAP (Na+K)-(Cl+HCO3): normal = HCO3 loss, > 15 = addition of a new acid)

49

pH: 7.05, PaCO2: 56, HCO3: 16


  Respiratory acidosis

  Metabolic acidosis

  Renal failure

  Both respiratory and metabolic acidosis

  Normal blood during intense exercise


Acidosis (extremely low pH) with high PaCO2 (respiratory acidosis) but also low bicarbonate indicating additional metabolic acidosis.