Ventilation (Trachte) - W1

Question 1

term for how gas (oxygen) gets to the alveoli

Answer 1

Ventilation

Question 2

Tidal volume

Answer 2

amount of air inspired and expired in routine breathing

500mL

Question 3

What is total lung volume and total lung capacity

Answer 3

lung volume = 4,000mL

lung capacity = 7,000mL

Question 4

Vital capacity

Answer 4

maximum amount of volume of air that can be exhaled after a maximum inspiration - 6000mL

Question 5

Residual volume

Answer 5

the amount remaining in lungs after maximal expiration

1500mL

Question 6

Functional residual capacity

Answer 6

amount remaining after typical exhalation

2,500mL

can’t measure directly but can calculate it

Question 7

How can we measure functional residual capacity?

Answer 7

Calculate:

• Gas dilution technique
• Plethysmograph

Question 8

Total ventilation =

Answer 8

amount of air entering and leaving the lung each minute

Question 9

Explain the gas dilution technique for calculating functional residual capacity

Answer 9

Use helium gas - how much goes in to lungs - CHECK DILUTION

normal dilution brings concentration down to 6.7% from 10%.

With BIGGER volume, dilution will go down further.

With smaller volume, dilution will be less.

Question 10

How do we calcuate alveolar ventilation

Answer 10

amount of CO2 exhaled in air/fractional concentration of CO2 in air

A = CO2/PCO2 x 1000

normal PCO2 = 40, CO2 = 200

Question 11

what is the normal fractional concentration of CO2 in air

Answer 11

5% or .05

Question 12

How is alveolar ventilation affected by respiratory alkalosis and respiratory acidosis?

Answer 12

• Acidosis - breathing less -> increase in PCO2 –> reduces alveolar ventilation
• Alkalosis - breathing more, reduce PCO2 –> increase alveolar ventilation

Question 13

How can we measure ANATOMICAL dead space volume?

Answer 13

• breathing pure O2
• the pure O2 will force N2 into the lung and out the dead space - exhalation will have NO NITROGEN from dead space, all will be coming from alveolar.
• Once nitrogen shows up, it’s more alveolar and it will plateau

Question 14

How can we measure physiologic dead space?

Answer 14

• need to measure the amount of ventilation NOT exchnage with blood - use CO2 dilution in exhaled air (only goes from blood to air)
• use fraction of CO2 in expired gas/fraction of CO2 in alveolar gas
  
  • ​CO2 exhaled ~27
  • PCO2 in blood ~40mmHg
  • should be 40-27/27 = 35%

Question 15

How much of breath does physiological dead space make up?

Answer 15

35% of breath

Question 16

What part of the lung is more ventilated and why?

Answer 16

Lower proportions better ventilated.

Gracity stretches the bottom of the lung more leading to a bigger change in pressure that leads to more flow into those areas.

Pulmonary artery doesn’t have to fight gravity as much so flow is better.

Question 17

In what diseases do you see a smaller vital capacity?

Answer 17

Restrictive lung disease.

COPD.

Question 18

How do you measure vital capacity?

Answer 18

Pulmonary function tests - may be smaller with restrictive lung diseases.