Respiratory Physiology

Question 1

What is the partial pressure of oxygen and carbon dioxide in the lungs at rest?

Answer 1

Oxygen is 100 +/- 2 mmHg

Carbon dioxide is 40 +/- mmHg

Question 2

What is the ventilation rate at rest and what does this equate to in terms of number of breaths and volume of air per breath?

Answer 2

Ventilation = 6L/min
12 breaths per min
500 ml/breath

Question 3

What is the approximate volume of oxygen consumed in one minute at rest?

Answer 3

250 ml

Question 4

What is the approximate volume of carbon dioxide expired per minute at rest?

Answer 4

200ml

Question 5

Which muscle is majorly important in inspiration?

Answer 5

Diaohragm

Question 6

When breathing at rest are inspiration and expiration active?

Answer 6

Inspiration is active

Expiration is passive - the result of elastic recoil

Question 7

How does the partial pressure of oxygen change in the blood as it passes through the lung?

Answer 7

The blood in the pulmonary artery has a low partial pressure of around perhaps 40mmHg and the blood in the pulmonary veins ahas a high partial pressure of oxygen of around 100mmHg

Question 8

What muscles pull the ribs outwards and upwards during inspiration?

Answer 8

External intercostal muscles

Question 9

In strenuous breathing are inspiration and expiration active?

Answer 9

Yes both are active

Question 10

Active expiration uses what muscles?

Answer 10

Abdominal muscles - rectus abdominus, internal oblique, external oblique, transverse abdominus
Internal intercostal muscles

Question 11

How do pleural, elastic recoil, alveolar, transpulmonary and barometric pressures change during inspiration?

Answer 11

Beginning of inspiration alveolar and barometric pressures are equal. Inspiratory muscles contract, increasing thoracic volume. Pleural pressure becomes more negative and transpulmonary pressure increases so lungs expand and alveolar volume increases. Alveolar pressure becomes lower than barometric pressure and the pressure gradient causes air to flow into the alveoli. At the end of inspiration, muscles stop contraction and the thorax and alveoli stop expanding so alveolar and barometric pressures become equal again

Question 12

How do pleural, elastic recoil, alveolar, transpulmonary and barometric pressures change during expiration?

Answer 12

At the beginning of expiration, thoracic volume decreases and pleural and transpulmonary pressures return to their pre-inspiration values. The thorax and lungs recoil due to elastic recoil pressure,and the air in the alveoli becomes compressed. The alveolar pressure becomes greater than the barometric pressure so air flows out of the lungs

Question 13

What is boyles law?

Answer 13

A law which states that in a closed system, volume and pressure are inversely proportional

Question 13

What is meant by compliance fo the lung?

Answer 13

Compliance is the degree to which a given change in pressure will expand the lung

Question 14

What effect does thickening of the lung have on lung compliance?

Answer 14

Decreases lung compliance

Question 15

What is the respiratory quotient?

Answer 15

The ratio of carbon dioxide produced to oxygen consumed

Question 16

What is ficks law?

Answer 16

Rate of diffusion = (diffusion constant x area over which diffusion occurs x pressure difference between sides of the membrane) / distance across which diffusion occurs

Question 17

In a mixture of gases, the pressure that each gas exerts is independent of the pressure which other gases exert. T/F?

Answer 17

True this is daltons law

Question 18

The amount of gas which dissolves in a fluid is directly proportional to the partial pressure of the gas with which the liquid is in equilibrium. T/F.

Answer 18

True this is henrys law

Question 19

Why is the diffusion of gases into or within liquids presented in terms of partial pressure rather than concentration?

Answer 19

The concentration of a gas in a liquid is also proportional to its solubility in that liquid

Question 20

Describe the process of gas exchange in the lung in terms of partial pressure

Answer 20

Blood that enters the pulmonary capillaries has a high partial pressure of carbon dioxide and a low partial pressure of oxygen. The difference in partial pressure of these gases on either side of the alveoli capillary membrane result in the net diffusion of oxygen from the alveoli into the blood and the net diffusion of carbon dioxide from the blood and into the alveoli. As this diffusion occurs, the partial pressure of oxygen in the capillary increases and that of carbon dioxide decreases. The net diffusion ceases when the capillary partial pressures of these gases becomes equal to that of the alveoli

Question 21

What factors determine the precise value of alveolar partial pressure of oxygen?

Answer 21

Partial pressure of oxygen in Atmospheric air
Rate fo alveolar ventilation
Rate of total body consumption of oxygen