Lecture 18: FEV₁/FVC Tests (Exam III)

Question 1

What is the Bohr Equation?

Answer 1

V_DCO₂ / V_T = (P_ACO₂ - P_ĒCO₂) ÷ P_ACO₂

Question 2

What is the Bohr equation used to find?

Answer 2

Total Dead Space

Question 3

Give an example of a Bohr equation with numbers.

Answer 3

V_TotalDS / V_T = (40mmHg - 28mmHg) ÷ 40mmHg

0.3 = V_TotalDS ÷ 500mL

V_TotalDS = 150mL

Question 4

How would one find alveolar dead space?

Answer 4

V_AlveolarDS = V_TotalDS - V_AnatomicDS

Question 5

How can anatomical dead space be estimated?

Answer 5

1mL of deadspace per 1lb of body weight

(Ex. 200lbs = 200mL anatomic deadspace)

Question 6

A 100kg patient presents with a P_ĒCO₂ of 25mmHg, a V_T of 600mls, and a PaCO₂ of 42mmHg. What would the estimated alveolar dead space of this patient be?

Answer 6

V_A = ?
V_T = 600mls
V_Anatomic = 220mls (100kg x 2.2 = 220lbs)

V_D ÷ 600mls = (42 - 25) ÷ 42
V_D = 242.86mls

V_A = 22.86mls (242.86mls - 220mls)

Question 7

If there is no shunting present then P_ACO₂ should = ____________.

Answer 7

PaCO₂

Question 8

If ĒCO₂ (mixed expired CO₂) is lower than expected, what conclusion could one likely draw?

Answer 8

There is increased dead space.

likely V_AlveolarD

Question 9

What would you expect from the flow-volume loop depicted below?

Answer 9

Normal

Question 10

What would you expect from the flow-volume loop depicted below?

Answer 10

Restrictive Disease

Question 11

What would you expect from the flow-volume loop depicted below?

Answer 11

Obstructive Disease

Question 12

What would you expect from the flow-volume loop depicted below?

Answer 12

Fixed Obstruction (Ex. ETT)

Question 13

What would you expect from the flow-volume loop depicted below?

Answer 13

Variable Extrathoracic Obstruction

Question 14

What would you expect from the flow-volume loop depicted below?

Answer 14

Variable Intrathoracic Obstruction

Peaked beginning likely due to emphysema

Question 15

What is FEV₁ ?

Answer 15

% of VC expired in 1 second

Question 16

What is an ideal FEV₁ assuming VC = 4.5L?

Answer 16

FEV₁ = 3.6L

Question 17

What is FEF_25-75% ?

Answer 17

Slope of line from once 25% of air has been expired to 75% of air expired.

Question 18

What would a gradually sloped FEF_25-75% (such as the one below) indicate?

Answer 18

Obstructive disease

Question 19

What would a steep sloped FEF_25-75% (such as the one below) indicate?

Answer 19

Normal

Question 20

FEV₁ could largely be considered an indicator of _____ airway health, whereas FEF_25-75% would be more indicative of ______ airway health.

Answer 20

large; small

FEV₁ = large airways
FEF_25-75% = small airways.

Question 21

What is the Vital Capacity of the patient from the graph below?

Answer 21

VC = 3.75L (ish)

Question 22

What is the FEV₁ of the patient from the graph below?

Answer 22

FEV₁ ≈ 1.5L

Question 23

What is the FEV₁/FVC of the patient from the graph below?

Answer 23

FEV₁ = 1.5
FVC = 3.75

1.5 ÷ 3.75 = 40%

Question 24

What is a normal FEV₁/FVC ?

Answer 24

80%

Question 25

What is the FEV₁ of the black line below?

Answer 25

3.6L

Question 26

What is the FEV₁ of the blue line below?

Answer 26

1.5L

Question 27

The two graphs below would be indicative of what?

Answer 27

FEV₁ / FVC = 3.8 ÷ 5 = 76%

Normal Physiology

Question 28

The two graphs below would be indicative of what?

Answer 28

FEV₁ / FVC = 2.5 ÷ 3 = 83%

Restrictive Disease

Question 29

The two graphs below would be indicative of what?

Answer 29

FEV₁ / FVC = 1.5 ÷ 3.5 = 43%

Obstructive Disease

Question 30

What FEV₁ / FVC would be considered pathologic?

Answer 30

< 70%

Question 31

Calculate the FEV₁ / FVC of the green line below.

What is this indicative of?

Answer 31

VC = 5 - 1.5 = 3.5
FEV₁ = 3

FEV₁ / FVC = 3÷3.5 ≈ 86%

Normal or Restrictive disease

Question 32

Calculate the FEV₁ / FVC of the red line below.

What is this indicative of?

Answer 32

VC = 5 - 0 = 5L
FEV₁ = 4L

FEV₁ / FVC = 4÷5 ≈ 80%

Normal

Question 33

What is abnormal about the flow-volume loop below?

Answer 33

Normal breathing should be closer to FRC

Question 34

What is the formula for Total Respiratory System Compliance?

Answer 34

• C_RS = Total Compliance of the Respiratory System
• C_L = Compliance of the tissue.
• C_CW = Compliance of the chest wall (i.e. ribs).

Question 35

What is the formula for Total Respiratory System Compliance?

Answer 35

• C_RS = Total Compliance of the Respiratory System
• C_L = Compliance of the tissue.
• C_CW = Compliance of the chest wall (i.e. ribs).

Question 36

What two factors oppose negative pressure exerted by P_IP ?

Answer 36

• P_ER (Tissues resistance to stretching)
• C_CW (ribcage resistance to expansion)

Question 37

What is the compliance of the respiratory system at FRC?

Answer 37

0.1 L/cmH₂O

Question 38

Solve for Respiratory System Compliance.

Answer 38

• C_L = 0.2
• C_CW = 0.2
• x = C_RS

(1÷x) = (1÷0.2) + (1÷0.2)
↓
(1÷0.1) = (1÷0.2) + (1÷0.2)
↓
C_{TotalCompliance(RS)} = 0.1L / cmH₂O

Question 39

How will body positioning affect ventilation at FRC?

Answer 39

• Upright: ribs assist ventilation
• Supine: ribs impede ventilation.

Question 40

If a lung was completely blocked off, what would occur to compliance?

Answer 40

Compliance would be cut in ½.

Question 41

Note: If you’re using my cards, I won’t be making new notecards over concepts we already discussed. I’ll be studying my notecards from the previous test. Just a heads up.