Lecture 6- Other mechanisms facilitating oxygen delivery to tissues

Question 1

if the oxygen dissociation curve shifts to the right

Answer 1

lower affinity- will let go of oxygen more readily but also bind less readily

Question 2

if the oxygen dissociation curve shifts to the left

Answer 2

higher affinity- will let go of oxygen less readily but also bind more readily

Question 3

factors that will push the oxygen dissociation curve to the right

Answer 3

• increased temp
• increased 2,3-DPG
• increase H +

Question 4

Bohr effect

Answer 4

o Low pH (increased H+) promotes T-state of Hb
o Hb has a lower affinity for O2
o Metabolically active tissue have a lower pH

Question 5

higher temp

Answer 5

o When temp goes up the T state is promoted  metabolically active tissue has a higher temp

Question 6

increased 2,3-DPG

Answer 6

o Disphosphoglycerate
o 2,3-DPG is an intermediate of RBC glycolysis normally rapidly consumed but in hypoxia RBC production of 2,3 DPG increases
o Facilitates O2 unloading in tissues
 Increased with anaemia and high altitude
 2,3-DPG levels drop in stored blood due to refrigeration

Question 7

what factors will cause the graph to shift to the left

Answer 7

• Decreased temp
• Decreased 2,3-DPG
• Increased pH (decreased H+)
• CO

Question 8

CO

Answer 8

o Reacts with hb to form COHb
o CO 200 times affinity for Hb as oxygen
 Reduced oxygen transport and total oxygen content
 Binds irreversibly
o CO monoxide increases affinity of unaffected subunits for oxygen
 Leftward shift in oxy-haemoglobin dissociation curve
 Reduced oxygen release peripheral tissue

Question 9

fatal if HbCO is above

Answer 9

50%

Question 10

why are children at increased risk of succumbing to CO poisoning

Answer 10

• Children at increased risk partly because they breathe faster

Question 11

CO poisoning will not

Answer 11

decrease PaO2 (free- oxygen, not bound to Hb)

Question 12

signs and symptoms of CO poisoning

Answer 12

o	Headache
o	Nausea
o	Vomiting
o	Slurred speech
o	Confusion
-	Initially may not have many resp symptoms

Question 13

difference between hypoxaemia and hypoxia

Answer 13

Hypoxaemia- low PaO2 in arterial blood

Hypoxia- low O2 levels in body or tissues

Question 14

hypoxaemia

Answer 14

Hypoxaemia- low PaO2 in arterial blood

Question 15

Hypoxia

Answer 15

low O2 levels in body or tissues

Question 16

If PaO2 levels are low, not all the Hb will be saturated=

Answer 16

both hypoxia and hypoxaemia

Question 17

If Hb levels are low, not enough

Answer 17

O2 will be present in the blood

Question 18

conditions such as…… can reduce bloow flow- peripheral

Answer 18

shock

Question 19

when tissues use O2 faster than it is delivered

Answer 19

o Peripheral arterial disease
o Raynauds
o Congestive heart failure with low CO

Question 20

Hypoxia secondary to anaemia

Answer 20

• PaO2 will be normal, O2 saturation will be normal

Question 21

Cyanosis

Answer 21

• Bluish colouration due to unsaturated Hb (<85 or 90%)

- Deoxygenated Hb is less red than oxygenated hb

Question 22

central cynosis

Answer 22

o Mouth, tongue, lips, mucous membrane

o Due to poorly saturated blood In systemic circulation

Question 23

peripheral cynosis

Answer 23

o Hands or feet

o Due to poor local circulation

Question 24

what can be used to detect the level of Hb saturation in the blood

Answer 24

pulse oximetry

Question 25

pulse oximetry

Answer 25

• Detects difference in absorption of light between oxygenated and deoxygenated Hb
• Only detects pulsatile (just in arteries not tissue) arterial blood levels
• Can’t detect tissue oxygen levels or non-pulsatile venous blood
• Regular two wave length pulse oximeter can’t detect carboxy- haemoglobin (CO-Hb) – will report normal saturation with CO-Hb
• Can’t give information about Hb levels
• Two wave length pulse oximeter wont detect CO bound to haemoglobin