Equations

Question 1

Equation for Transpulmonary pressure PTP

Answer 1

PTP = Plung - PIPdifference between:air pressure in the lung and the intrapleural pressure in the water in the intrapleural space

Question 2

Equation for compliance C

Answer 2

C = ΔV / ΔP

Question 3

LaPlace’s Formula

Answer 3

P= 2 x T /r surface tension creates a tendency for small alveoli to empty their air down the pressure gradient into larger ones, leading to the collapse of the small ones.

Question 4

Eq for air Flow in airways

Answer 4

Flow = ΔP/RFlow is proportional to P difference

Question 5

Is Resistance directly proportional or inversely proportional to radius?

Answer 5

R = 1/r^4inversely

Question 6

Eq for minute ventilation- typical rates?

Answer 6

Minute Ventilation = Tidal Vol (TV) x Breathing rate (RR)

0.5 L/breath x 12 breaths/min = 6L

Question 7

Eq for Vital Capacity (VC)

Answer 7

VC = TLC - RV

The volume of air exhaled after a maximal inspiration followed by a maximal expiration

Question 8

Winter’s formula

Answer 8

pCO2 = (1.5 * HCO3-) + 8 ±2

Question 9

Calculation of the A-a gradient

Answer 9

Alveolar gas equation to estimate PAO2:
PAO2 = [(Pb-PH2O) x FiO2] -PaCO2/R

In Denver P AO2 = [(630-47)0.21)] -PaCO2/0.8

PAO2 - PaO2

Question 10

How do we calculate PIO2?what is normal PIO2 at sea level and denver?

Answer 10

PIO2 = (PB – 47 Torr) × 0.21

150 Torr - sea level
120 Torr - denver

Question 11

Alveolar ventilation equation

Answer 11

PACO2 = V˙ CO2/ V˙ A * k

V˙ CO2 is the quantity of CO2 produced in one minute
V˙ A is the quantity of alveolar ventilation in one minute
K = 863 mmHG

Because PACO2 is essentially equivalent to PaCO2, one can also substitute PaCO2 for PACO2 in the equation.*note: this is the Rate limiting step dictating how much CO2 is removed

Question 12

CaO2 equation

Answer 12

CaO2 = (SaO2 × [Hb] X 1.39)*total concentration of oxygen, including hemoglobin-bound and freely dissolvedcomponents.

but we ignore that last part bc its so tiny

Question 13

Hypoxemia values

Answer 13

The definition of hypoxemia is a PaO2

Question 14

Equation for PAP

Answer 14

PAP = CO* PVR + LAP
Just move the equation around.
There are 3 things that go into PAP, so it makes sense that there are 3 ways that PAP can be affected

Question 15

Calculate PAO2 given known PACO2

Answer 15

PACO2 = (V˙ CO2) / (V˙ A) * k

PAO2 = PIO2 - (PACO2/R) + k

k = 863 mmHg

Question 16

Hyperpnia

• what is it?
• when would you see it?

Answer 16

increased depth of breathing in response to metabolic demand

High VA and Normal PaCO2

• exercise