Gas Transport in the Airways

Question 1

What is a healthy range for partial pressure of arterial oxygen content at sea level? In Denver?

Answer 1

90 - 100 Torr; 80 - 85 Torr

Question 2

Oxygen in the blood is not ________.

Answer 2

a gas, it is dissolved

Question 3

What is Dalton’s law?

Answer 3

P(IO2) = (P[B] – 47 Torr) x F(O2)

Question 4

What is P(A[O2])?

Answer 4

The partial pressure of oxygen in the alveoli

Question 5

What is the equation for pressure of oxygen in alveoli?

Answer 5

P(A[O2]) = P(I[O2]) –(PA[CO2]/R)

Question 6

What is R (in the equation for alveolar oxygen pressure)?

Answer 6

Respiratory exchange ratio; this represents the amount of CO2 produced for O2 consumed; it is always less than one, and it is lower for fats and proteins than carbohydrates

Question 7

What is average respiratory exchange ratio for a normal diet?

Answer 7

0.8

Question 8

If you are breathing 100% oxygen, then R = ____.

Answer 8

1, because all of the expended oxygen must be replaced by CO2 (and not N2)

Question 9

What is ideal arterial CO2 at sea level?

Answer 9

40 Torr

Question 10

There is near perfect equilibration of ________ CO2 with ________ CO2.

Answer 10

alveolar; arterial

Question 11

Describe the alveolar ventilation equation.

Answer 11

Pa(CO2) = (V[CO2]) / (V[A]) x k; this equation gives you arterial CO2 concentration from CO2 produced divided by alveolar ventilation

Question 12

The alveolar ventilation equation also gives you ___________.

Answer 12

Alveolar CO2, which can be plugged into the alveolar oxygen equation

Question 13

P(IO2) (in words) is __________; in formula is __________.

Answer 13

the partial pressure of inspired oxygen; P(IO2) = atmospheric pressure x percent of oxygen in the air

Question 14

The barometric pressure in Denver is roughly ___________.

Answer 14

630 Torr

Question 15

What is the P(IO2) of a person breathing 100% oxygen at sea level?

Answer 15

713 Torr, because P(B) at sea level = 760 Torr

Question 16

In words, what does the alveolar gas equation solve for?

Answer 16

It tells you the pressure of oxygen in the alveoli if you know the P(IO2) and the P(A[CO2]), which allows you to determine the A-a gradient of oxygen.

Question 17

At sea level, normal P(A[O2]) is _______.

Answer 17

100 Torr

Question 18

CO2 diffusion is _________; the rate-limiting step is _________.

Answer 18

fast; ventilation (that is, expelling CO2 from the lungs)

Question 19

Pa(CO2) = _________.

Answer 19

[(CO2 produced in one minute) / (alveolar ventilation in one minute)] x k; thus, Pa(CO2) is inversely related to alveolar ventilation

Question 20

What is hyperpnia?

Answer 20

A state of high ventilation with normal Pa(CO2)–such as is found during exercise, when CO2 levels rise

Question 21

What is hypoventilation?

Answer 21

Low ventilation and high Pa(CO2), such as can be produced by respiratory depression or severe obstructive disease

Question 22

What is hyperventilation?

Answer 22

High ventilation and low Pa(CO2), such as is found at high altitude or during anxiety attacks

Question 23

_________ does not vary with altitude.

Answer 23

Water pressure vapor

Question 24

Alveolar ventilation can be estimated by the following equation: __________.

Answer 24

V(A) = (V[CO2]) / (P[aCO2]) x k

Question 25

In Denver, the normal P(a[CO2]) is _________, because of increased ventilation secondary to chronic hypoxia.

Answer 25

30 - 40 Torr