Respiratory PFTs & Equations Flashcards Preview

AS - N932 Advanced Pathology > Respiratory PFTs & Equations > Flashcards

Flashcards in Respiratory PFTs & Equations Deck (33)
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1

FVC Male

4.8L

2

FVC Female

3.7L

3

FEV1

Forced expiratory volume in 1 second
Volume air forcefully exhaled
Normal 4L TLC 5L

4

FVC

Forced vital capacity
Volume air forcefully exhaled after deep inhalation

5

FEV1/FVC

75-80%
4L/5L

6

FEF 25-75

Measures airflow at midpoint forced expiration

7

DLCO

17-25mL/min/mmHg
Normal >75% predicted
Mild 60-75%
Moderate 40-60%
Severe <40%

8

Static Compliance

Cst = Vt / (Pplat - PEEP)
Normal 60-100mL/cmH2O

9

Dynamic Compliance

Cdyn = Vt / (PIP - PEEP)
Normal 50-100mL/cmH2O
PIP - peak airway pressure

10

Reynold's Number

Re = pvd/η
P - density
V - velocity
D - diameter
η - Viscosity
Laminar <2,000
Transitional 2,000-4,000
Turbulent >4,000

11

Closing Capacity

CV + RV
30% TLC
↑55% TLC 70yo

12

Fick's Law

Vgas = (D x SA x ΔP) / T

Diffusion coefficient = gas solubility / MW
Surface area
Partial pressure difference
Membrane thickness

13

PAO2

(PB - PH2O) x FiO2 - (PaCO2/RQ)
RQ = 0.8
Normal 80-100

14

Alveolar-Arterial Oxygen Gradient

PAO2 - PaO2
Normal 5-15mmHg

*Increases w/ age (20-30mmHg)

Directly proportional to shunt
Inversely proportional to PvO2

15

a/A Ratio

PaO2/PAO2
Normal >75%

16

Arterial Oxygen Content
CaO2

(Hgb x 1.34 x SaO2) + (PaO2 x 0.003)
Normal 20.4mL O2 per 100mL blood
CvO2 = 15mL normal extraction rate

17

Oxygen Delivery

DO2 = QT x CaO2 = 1,000mL/min
QT= CO
CaO2 200mL/min/L (20.4 x 10)

18

Oxygen Consumption

VO2 = QT x (CaO2 - CvO2)
= 5L/min x (200mL - 150mL)
= 250mL/min

19

Alveolar CO2 Tension
PACO2

PACO2 = VCO2/VA
PACO2 ≈ PaCO2

VCO2 - total CO2 production
VA - alveolar ventilation

PaCO2 35-45 adequate ventilation
<45 inadequate
<35 excessive

20

P:F Ratio

PaO2/FiO2
Normal 400-500
Mild ARDS <300
Moderate <200
Severe <100

21

Dalton's Law

Total pressure = P1 + P2 + P3 + PN

22

Henry's Law

Amount gas dissolved in liquid = directly proportional to the pressure applied to the gas as it overlies that liquid

23

Ptranspulmonary

Ptp = Palv - Pip

Palveolar
Pintrapleural

24

LaPlace

Pressure = (2 x tension) / radius

*Surfactant impact on surface tension

25

PACO2 vs. PaCO2 vs. ETCO2

PACO2 virtually identical to PaCO2
PACO2 or PaCO2 to ETCO2 gradient normally <5mmHg (2-5mmHg)

Normal PaCO2 35-45mmHg
Normal ETCO2 30-42mmHg

26

Minute Ventilation VE

Sum all Exhaled gas volume in 1min
VE = frequency x Vt ≈ 5L/min
RR x tidal volume

27

Alveolar Ventilation VA

VA = Frequency x (Vt - VD)
RR x (tidal volume - dead space) ≈ 4L/min

Not all Vt participates in gas exchange (conducting zone or dead space VD)

28

Anatomic Dead Space

Conducting zone

Adult 150mL
1/3 or 30% Vt
1mL/lb
2mL/kg

29

Alveolar Dead Space

Non-perfused alveoli

30

Physiologic Dead Space

Anatomic + alveolar dead space