Ventilation and Lung Volumes

Question 1

What effect does increasing lung compliance have on FRC?

Answer 1

It increases FRC

-not able to expel as much air

Question 2

What happens to lung compliance with age?

Answer 2

it decreases

Question 3

What is total lung capacity? What is the normal value?

Answer 3

max volume of gas that the lungs can contain

6-7 L

Question 4

What is the tidal volume? What is the normal value?

Answer 4

Volume of gas which flows into and then out with each breath

-500-600 mL

Question 5

How can tidal volume be increased?

Answer 5

exercise

Question 6

can tidal volume be measured by a spirometer?

Answer 6

Yes

Question 7

What is inspiratory reserve volume?

Answer 7

max volume of gas that can be inhaled from end-tidal inspiratory position

Question 8

What is expiratory reserve volume?

Answer 8

-volume of gas that can be exhaled from end-tidal expiratory position

Question 9

What is residual volume?

Answer 9

volume of gas contained in the lungs after max force of expiration
-can’t be exhaled

Question 10

What is vital capacity?

Answer 10

-max volume of gas that can be exhaled after normal inspiration

Question 11

What is inspiratory reserve capacity? (IC)

Answer 11

max volume of gas that can be inhaled from resting expiratory position

Question 12

What is the formula for vital capacity ?

Answer 12

VC= IRV +Vt + ERV = TLC- RV

Question 13

What is the formula for IC?

Answer 13

IC= VT+IRV = TLC - FRC

Question 14

What is functional residual capacity?

Answer 14

Volume of gas in the lungs after normal expiration

-when diaphragm and chest muscles are relaxed

Question 15

Can FRC be measured by a spirometer?

Answer 15

NO - it includes RV

Question 16

What is the ultimate goal of using a N2 washout?

Answer 16

You want to measure FRC

• can’t measure with a spirometer
• this value is a good indicator of obstructive or restrictive diseases

Question 17

What are the steps involved in N2 washout ?

Answer 17

1. subject breathes normal air
   - N2 fraction is measured
2. at the end of eupneic breathing - lung is at FRC and subject breathes in 100% O2
   - for at least 7 minutes
   - washes out all N2 from the lung
3. expired gas is collected in spirometer

Question 18

What is the issue with using N2 washout to record FRC?

Answer 18

• if there are regions in the lung with trapped air, this volume won’t be measured
• FRC is underestimated

Question 19

do we have to know the FRC equation for N2 washout, or the pletysmograph equation ????

Answer 19

not sure, making this flash card to remind us to memorize them if need be

Question 20

What is a plethysmograph?

Answer 20

a gas-tight chamber in which a patient sits in and breathes through a tube leading to outside
-used to measure FRC

Question 21

As a patient expires against a pressure transducer with a closed valve in a pletysmograph, what happens to their lung volume and P?

Answer 21

• the volume of the lung is compressed

- the P of the lung is raised

Question 22

Since the chamber is gas tight, what happens to the air in the box outside the subject’s body as they breathe air to the outside?

Answer 22

• the air will expand

- this change in volume is exactly equal to the amount of compression of air in the lungs

Question 23

What is the amount of dead space in mL approximated as ?

Answer 23

equal to the subject’s weight in pounds

Question 24

What is total ventilation equal to?

Answer 24

Dead space ventilation plus alveolar ventilation

Question 25

Hypoventilation results in what two consequences?

Answer 25

1. alveolar hypercapnea - inc PACO2 | 2. hypoxia - dec PAO2

Question 26

Hyperventilation results in what two consequences?

Answer 26

1. alveolar hypocapnea - dec PACO2 | 2. hyperoxia - inc PAO2

Question 27

Increasing oxygen consumption, has what effect on alveolar oxygen?

Answer 27

decreases it

Question 28

What does R mean in the equation: | PAO2=PlungO2-PACO2/R

Answer 28

-ratio of O2 consumption to production

Question 29

Vt is about what percentage of TLC?

Answer 29

only about 10% | -volume of air going into and out of the lung with each breath = small fraction of air in the lung

Question 30

About by how much do the PO2 and PCO2 oscillate by in alveoli during eupnea?

Answer 30

1-2 mmHg

Question 31

Why does the PO2 first decrease when you first inspire?

Answer 31

O2 is going into blood when air is going through the dead space

Question 32

What is a single breath analysis of dead space?

Answer 32

-subject inspires air containing neglible CO2 and then exhales into a spirometer -fraction of CO2 is measured (contains CO2 from the body)

Question 33

As the subject exhales, what does the FECO2 rise to and plateau at?

Answer 33

5%

Question 34

Why when the patient first exhale, does the first gas contain negligibly low CO2?

Answer 34

gas comes from the anatomic dead space

Question 35

What does the time of the midpoint of the rise of FECO2 correspond to?

Answer 35

the time at which all of the dead space air would be expired -if there was a sharp boundary btwn dead space gas and alveolar gas

Question 36

What does the alveolar ventilation equation predict?

Answer 36

It describes the dependence of alveolar and arterial Pco2 on alveolar ventilation

Question 37

What does the alveolar gas equation predict?

Answer 37

Predicts the alveolar Po2, based on the he alveolar Pco2