Pulm

Question 1

Conducting zone/Anatomic dead space: number of generations, and volume

Answer 1

Generations 1-16, 150mL

Question 2

Respiratory zone: generations, volume

Answer 2

Generations 17-20, 2.5-3L

Question 3

4 main, non-overlapping lung volumes

Answer 3

RV: Reserve volume, ERV: Expiratory Reserve Volume, TV: Tidal Volume, IRV: Inspiratory Reserve Volume

Question 4

What is FRC, TLC, IC, FVC/VC?

Answer 4

FRC = Functional Residual Capacity = RV + ERV (volume of the lung at the end of tidal expiration)
TLC = Total Lung Capacity = RV+ERV+TV+IRV
IC = Inspiratory Capacity = TV + IRV
FVC/VC = (Forced) Vital Capacity) = IRV + TV + ERV

Question 5

Which lung volume cannot be measured with spirometry? Which capacities cannot be measured with a spirometer either?

Answer 5

RV. Thus any capacity that includes RV cannot be measured with a spirometer either (FRC, TLC)

Question 6

How is compliance calculated?

Answer 6

Slope of the deflation curve of a pressure/volume curve of the lung. Change in volume over the change in pressure.

Question 7

How is specific lung compliance calculated? What is is for?

Answer 7

Compliance of lung/volume of lung. Adjusts compliance for lung size. Smaller people/children have smaller/less compliant lungs, but not unusually so.

Question 8

What are the two opposing pressure that act on the lung to determine lung volume?

Answer 8

Elastic recoil of the lung pulling and the push or pull of the chest wall (depending on chest volume).

Question 9

At FRC, what are the pressures pushing/pulling on the respiratory system to determine lung volume? Give exact-ish numbers

Answer 9

At FRC, elastic recoil of the lung is pulling inwards trying to collapse the lung, creating a pressure of +5-6 cmH2O. The chest wall is pulling outwards on the respiratory system, creating a pressure of -5-6 cmH2O. So at FRC, total pressure on the respiratory system is atmospheric, 0 cmH20.

Question 10

What is the pressure across the respiratory system at the end of inspiration and expiration (times of no air-flow)?

Answer 10

Zero.

Question 11

Calculation for flow rate

Answer 11

(Change in pressure * radius^4)/(density * viscosity)

Question 12

What is airway resistance directly and inversely proportional to?

Answer 12

Directly proportional to airway length and gas viscosity. Inversely proportional to airway radius to the fourth power.

Question 13

Where is airway resistance highest?

Answer 13

Highest in the first six generations of airways

Question 14

Where is airway resistance lowest?

Answer 14

Lowest in the respiratory bronchioles and lower. Though these airways are smaller, together have a much larger total cross sectional area and much lower resistance.

Question 15

Which generations of airways have turbulent flow?

Answer 15

Generations 0-9

Question 16

Which generations of airways have laminar flow?

Answer 16

Generations 10-16

Question 17

Which generations of airways have diffusive ‘flow’?

Answer 17

Generations 17-20

Question 18

What is the most important pulmonary function test and what is the normal range?

Answer 18

FEV1/FVC ratio, the ratio of Forced Expiratory Volume in 1 second to Forced Vital Capacity. Normal is >75%.

Question 19

What is dynamic compression and how does it create flow limitation?

Answer 19

Dynamic compression occurs during forced expiration when pleural pressure outside the airway, is greater than the pressure inside the airway. Expiration rate is then limited by the difference between alveolar pressure and pleural pressure. This is flow limitation. No matter how hard you exhale, dynamic compression means air flow is limited and is therefor effort-independent.

Question 20

What is the equal pressure point? Where is this in normal people vs people with COPD?

Answer 20

Point where pressure inside the airways and surrounding the airways is the same. In nl people, this is in an airway with cartilage that helps the airway resist compression/collapse. In people with COPD, this point is closer to the alveoli, which have no ability to resist the surrounding pressure, and can lead to premature collapse/air trapping seen in people with COPD.

Question 21

What are the two main components of respiratory work?

Answer 21

Elastic work (overcoming elastic recoil of the lungs, expanding the chest wall, dispalce abd organs) and flow-resistance work (airflow resistance, and lobe-lobe viscous resistance)

Question 22

How is total respiratory work estimated? What shape is the total respiratory work curve (on the respiratory rate vs mechanical work graph)? Where on the curve is normal tidal volume found?

Answer 22

Estimated as the sum of elastic work and non-elastic work. The curve is U-shaped. Nl tidal volume is found at the lowpoint of the curve, where respiratory work is the smallest.

Question 23

What is barometric pressure (in mmHg) at sea level?

Answer 23

760 mmHg

Question 24

What is water vapor pressure of inhaled air at sea level?

Answer 24

47 mmHg

Question 25

What is FO2?

Answer 25

21%

Question 26

How is the PO2 in the trachea calculated?

Answer 26

PO2trachea = (Patmospheric - Pvapor) * FO2

Nl values: 150 mmHg = (760mmHg - 47mmHg) * 0.21

Question 27

What is the alveolar gas equation?

Answer 27

PO2alveolar = PO2inspired - (PCO2/gas exchange ratio)

Nl values: 100mmHg = 150 mmHg - 40mmHg/0.8

Question 28

What is the relationship between alveolar ventilation, CO2 ventilation, and PCO2? What happens in PCO2 if alveolar ventilation is doubled?

Answer 28

Va = VCO2/PCO2. If alveolar ventilation is doubled, partial pressure of CO2 in the alveoli (and in the arterial system) is halved.