6 Oxygen in the Blood Flashcards
Does this diagram show the dissociation curve for haemoglobin or myoglobin?
What are the 2 haemoglobin ‘moods’?
-
Tense - low affinty for oxygen - T state
- When partial pressure of O2= low
(as each O2 binds, molecule more relaxed)
- Relaxed- high affinity for oxygen - R state
Why is the haemoglobin dissociation curve sigmoid shaped?
Hb molecule ‘more stable’ with either 4 O2 bond or none.
What is the normal oxygen content of th blood?
8.8 mmol/L
If a patient is anaemic, what will be the oxygen content of their blood?
Lower than normal
(BUT pO2 will be normal)
What value should pO2 in tissues not fall below? Why is this?
3 kPa as pO2 must be high enough to drive diffusion of O2 into cells
(BUT- HIGHER CAPILLARY DENSITY: lower pO2 can fall as oxygen doesn’t have to diffuse so far)
Give an example of an organ in the body that is very metabolically active and has a high capillary density.
Heart
What is the Bohr shift?
Promotes release of O2 by Hb
pH and temperature affect affinity for haemoglobin
pH lower in metabolically active tissues- more O2 given up
temperature higher - more O2 given up
What effect does 2,3-Bisphosphoglycerate have on the Hb dissociation curve?
Increase in 2,3-BPG levels shifts curve to right
2,3-BPG levels increase in anaemia / at high altitude
More O2 given up at tissues
(2,3-BPG levels drop in stored blood)
What’s the difference between hypoxemia and hypoxia?
Hypoxemia= low pO2 in arterial blood
Hypoxia= low oxygen levels in body/tissues
What is cyanosis?
Bluish colouration due to unsaturated haemoglobin
Peripheral: poor local circulation
Central: Poorly saturated blood in systemic circulation
What is pulse oximetry used for?
Detect level of Hb saturation (not amount of Hb present)
Only detects pulsatile arterial blood
Which artery is an arterial blood gas sample usually taken from?
Radial artery
In a healthy patient, what would the concentration of oxygen be bound to haemoglobin?
8.8 mmol/L of oxygen bound to haemoglobin in a healthy patient
