Respiratory3

Question 1

How do you determine physiological dead space (VD)?

Answer 1

VD = VT x [(PaCO2 - PECO2)/PaCO2]

VT = tidal volume
PaCO2 = arterial PCO2
PECO2 = expired air PCO2

“Taco Paco, PEco, Paco - refers to order of variables in equation)”

Question 2

What is physiologic dead space?

Answer 2

Anatomic dead space of conducting airways PLUS function dead space in alveoli

*Volume of inspired air that does not take part in gas exchange

Question 3

What region of the lung is the Largest contributor to functional dead space?

Answer 3

Apex (healthy lung)

Question 4

Tendency for lungs to collapse ______ and chest wall to spring _______.

Answer 4

Lungs - Inward

Chest wall - Outward

Question 5

At Functional Residual Capacity (FRC) what are airway and alveolar pressures?

Answer 5

ZERO

*Intrapleural pressure is negative – Prevents pneumothorax

Question 6

What is lung Compliance?

Answer 6

Change in lung volume for a given change in pressure

Question 7

What pathologies cause a DEcrease in lung compliance?

Answer 7

Pulmonary Fibrosis
Pneumonia
Pulmonary Edema

Question 8

What pathologies cause an INcrease in lung compliance?

Answer 8

Emphysema

Normal aging

Question 9

What makes up Hemoglobin?

Answer 9

4 polypeptide subunits

• 2 alpha
• 2 beta

Question 10

What are the 2 forms of hemoglobin? What are their relative affinities for O2?

Answer 10

T (taut) – Low affinity for O2 – Tissues

R (relaxed) – High affinity for O2 – Lungs

Question 11

What molecules favor T (taut) form over R (relaxed) form?

Answer 11

INcreased:

• Cl-
• H+
• CO2
• 2,3-BPG
• Temperature

*Shifts dissociation curve to right – leading to INcreased O2 unloading

Question 12

Describe fetal hemoglobin.

Answer 12

• 2 alpha & 2 gamma subunits
• Lower affinity for 2,3-BPG than adult Hb
• Higher affinity for O2 than adult Hb

Question 13

What are the 2 forms of modified hemoglobin?

What does it lead to?

Answer 13

Methemoglobin
Carboxyhemoglobin

Leads to tissue Hypoxia:

• DEcreased O2 saturation
• DEcreased O2 content

Question 14

Define Methemoglobin.

Answer 14

Oxidized form of hemoglobin (ferric, Fe3+)
Does NOT bind O2 as readily
INcreased affinity for Cyanide

Question 15

How do you treat cyanide poisening?

Answer 15

Use Nitrates to oxidize Hb to methemoglobin
This binds Cyanide
Allowing cytochorome oxidase to function
Use Thiosulfate to bind this Cyanide
Forming thiocyanate –> Renally excreted

Question 16

How do you treat Methoglobinemia?

Answer 16

Methylene blue

Question 17

Define Carboxyhemoglobin.

Answer 17

Form of Hb bound to CO (carbon monoxide) in place of O2

*CO has a 200X greater affinity for O2 for Hb

Question 18

What does CO poisening cause?

Answer 18

DEcreased oxygen-binding capacity
-Left shift in the O2-Hb dissociation curve
DEcreased oxygen unloading in tissues

Question 19

What happens when the O2-Hb dissociation curve shifts to the Right?

Answer 19

DEcreased affinity of Hb for O2

- Facilitates unloading of O2 to tissue

Question 20

What does Fetal O2-Hb dissociation curve look like compared to adult O2-Hb curve?

Answer 20

It is shifted to the Left

*Hb has higher affinity for O2 than adult

Question 21

What are the causes of a Right Shift in the O2-Hb dissociation curve?

Answer 21

“C-BEAT”

CO2
BPG (2,3-BPG)
Exercise
Acid/Altitude
Temperature