Self-test questions: Chapter 34

. The anatomical dead space is the volume of air taken in during a breath that does not enter the alveoli.

True

False

. The physiological dead space is the volume of air taken in during a breath that does not take part in gas exchange.

True

False

. The volume of the physiological dead space is the same as that of the anatomical dead space.

True

False

. The size of the anatomical dead space depends on the tidal volume

True

False

. In an upright lung, the alveolar ventilation is normally highest at the apex of the lungs.

True

False

. Which of the following statements regarding the pulmonary circulation are correct?

The pressures in the pulmonary arteries are about half of those in the systemic arteries.

The resistance of the pulmonary circulation falls as the pulmonary blood flow increases.

The mean pressure in the pulmonary arteries rises as cardiac output increases.

The pattern of pulmonary blood flow is independent of posture

. Which of the following statements regarding the respiratory system are true?

Half the cardiac output passes through the lungs

In an upright man, pulmonary blood flow is greatest at the base of the lung

The lungs inactivate all circulating vasoactive materials

The vital capacity is equal to the total lung capacity

At the functional residual volume, the elastic recoil of the lungs is balanced by the elastic forces tending to expand the chest

. Which of the following statements about ventilation and gas exchange are true?

The

ratio for a subject in a sitting position increases with distance above the base of the lung.

The regional variation in

ratios is much greater in subjects who are lying down.

In a healthy lung, the distance between the alveolar air and the blood in the pulmonary capillaries is less than 1μm

The diffusing capacity for carbon dioxide in the lungs is similar to that of oxygen

. Equal volumes of blood from hypoventilated and normally ventilated regions of a lung become mixed in a pulmonary vein. If the PO₂ of the blood draining the hypoventilated region is 8 kPa (60 mm Hg) and that of the normally ventilated region is 13.3 kPa (100 mm Hg) what will the PO₂ of the mixed blood be? Assume the haemoglobin to be 15 g dl^-1. It may be helpful to refer to Fig 25.11.

10.7 kPa (80 mm Hg)

12 kPa (90 mm Hg),

9.3 kPa (70 mm Hg

8 kPa (60 mm Hg)

. During exercise a subject has a tidal volume of 1.58 litres and the CO2 in the expired air is 4.5 percent. A subsequent measurement shows the alveolar air to contain 5.2 percent CO2. Which of the values below is the correct value for physiological dead space? Use the Bohr equation to calculate the dead space.

0.15 litres

0.18 litres

0.21 litres

0.28 litres

Self-test questions: Chapter 34

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