Respiratory Phys - Hb

Question 1

Hemoglobin is composed of:

Answer 1

4 polypeptide subunits (2 alpha and 2 beta)

Question 2

2 forms of Hb

Answer 2

T (taut) and R (relaxed)

Question 3

T (taut) form of Hb has…

Answer 3

low affinity for O2

Taut in Tissues

Question 4

R (relaxed) form of Hb has…

Answer 4

high affinity for O2 (300x)

Relaxed in Respiratory tract

Question 5

Factors that favor Taut form of Hb:

Answer 5

Increased Cl-, H+, CO2, 2,3-BPG, and temperature.
Shifts dissociation curve RIGHT.
Leads to increased O2 unloading.

Question 6

Fetal Hb is composed of:

Answer 6

2 alpha and 2 gamma subunits.

Question 7

Fetal Hb affinity for 2,3-BPG:

Answer 7

lower affinity for 2,3-BPG than adult Hb

Question 8

Fetal Hb affinity for O2:

Answer 8

higher affinity for O2 than adult O2

Question 9

Hemoglobin modifications

Answer 9

Lead to tissue hypoxia from decreased O2 saturation and decreased O2 content

Question 10

Iron form in Methemoglobin

Answer 10

Oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has increased affinity for cyanide.

Question 11

Iron in normal Hb is in what state

Answer 11

Fe2+ (ferrous, reduced)

Just the 2 of us: ferroUS is fe2+

Question 12

Methemoglobin may present with:

Answer 12

Cyanosis and chocolate-colored blood

Question 13

How do you treat cyanide poisoning?

Answer 13

1. Nitrites to oxidize Hb to methemoglobin, which binds CN.

2. Use thiosulfate to bind this CN, forming thiocyanate, which is renally excreted.

Question 14

Nitrites cause poisoning by

Answer 14

oxidizing Fe2+ to Fe3+

Question 15

Antidote to Methemoglobinemia

Answer 15

Methylene blue

Also can use Vitamin C

Question 16

Methylene blue

Answer 16

Used to treat Methemoglobinemia because at pharmacologic doses it has reducing properties.
Given IV
Converts Fe3+ back to Fe2+

Question 17

Carboxyhemoglobin

Answer 17

Form of Hb bound to CO in place of O2.

Question 18

CO bound Hb causes:

Answer 18

Decreased oxygen-binding capacity with LEFT SHIFT in dissociation curve
Decreased O2 unloading in tissues

Question 19

Affinity of CO to Hb

Answer 19

200x greater than O2 for Hb

Question 20

Positive Cooperativity of Hb

Answer 20

Tetrameric Hb molecule can bind 4 O2 molecules and has higher affinity for each subsequent O2 molecule bound

Question 21

Oxygen-Hb Dissociation curve: shape, x, and y axes

Answer 21

sigmoidal shape due to positive cooperativity
Hb saturation (%) on y axis
PO2 (mmHg) on x axis

Question 22

Right shift of O2-Hb Dissociation curve causes

Answer 22

Decreased affinity of Hb for O2 (facilitates unloading at tissues)

Question 23

Factors that cause RIGHT shift:

Answer 23

BAT ACE (increase in these)
BPG (2-3BPG)
Altitude
Temperature
Acid
CO2
Exercise

Question 24

What causes a LEFT shift?

Answer 24

A decrease in all factors (including H+)

Question 25

Myoglobin structure

Answer 25

Monomeric, does not show positive cooperativity.

Curve lacks sigmoidal appearance

Question 26

Causes of Methemoglobin:

Answer 26

Commonly caused by medications:
**Nitrates/Nitrites (most common)
Anti-malarials: Chloroquine, Primaquine
Dapsone
Sulfonamides
Local Anesthetics: Lidocaine
Metoclopramide

Question 27

Gradually lowers Methemoglobin:

Answer 27

Cimetidine

Question 28

What’s scary about diagnosing someone with CO poisoning?

Answer 28

Can’t diagnose with pulse ox!!

Question 29

Fetal O2-Hb Dissociation curve:

Answer 29

LEFT shifted from normal because LOWER affinity for 2,3-BPG and HIGHER affinity for O2

Question 30

H+ ions can be buffered by

Answer 30

Hg

Question 31

Treat CO poisoning with:

Answer 31

100% O2 and hyperbaric O2