L7 WEEK 1 HYPOXEMIAS Flashcards
Reduced tissue oxygenation
hypoxia
Name 4 types of hypoxia
- Anaemic hypoxia: low RBCs
- Hypoxic hypoxia: low pressures of arterial oxygen
- stagnant hypoxia: reduced blood flow
- histotoxic hypoxia- Reduced oxygen utilization by cells
You will see anaemic hypoxia as a result of…..
- Reduced RBC numbers
- Abnormal RBCs
- Abnormal Hb
- Carbon monoxide poisoning
- PAO2 normal
- PaO2 normal
- (a-v)O2 normal
- Hb decreased
Anaemic hypoxia
- PaO2 normal
- PvO2 decreased
- (a-v)O2 increased
Stagnant hypoxia
- caused by reduced cardiac output
how does stagnant hypoxia come about?
Left heart failure
- Reduced pump action of the LV leading to reduced cardiac output.
How does histotoxic hypoxia come about?
Caused by cyanide poisoning
Cyanide blocks oxidative phosphorylation
Tissues unable to use Oxygen
PaO2 normal
CaO2 normal
CvO2 increased
(a-v) O2 decreased
Histotoxic hypoxia
What is the ‘at rest’ volume of of arterial and venous oxygen?
At rest CaO2 = 200ml/L blood
CvO2 = 150ml/L blood
(a-v)O2= 50 ml/L blood
What causes hypoxic hypoxia?
Ventilation defect
Diffusion defect
Perfusion defect
What are the causes of ventilation defect?
- Restrictive lung problem
- Obstructive lung problem
- Injury to respiratory centre
- Spinal cord injury
- Myasthenia gravis
Measures diffusion defect
PAO2-PaO2
FEV1/FVC<70%
obstructive disease
*problem exhaling
What are the causes of diffussion defect? (the widening of P(A– a)O2 difference
- Interstitial fibrosis
- Lung oedema
-Left heart failure
-Pulmonary hypertension
What causes perfussion defect?
Reduced blood flow to pulmonary capillaries:
Caused by:
-Reduced BP
-Shock
-Hemorrhage
-Pulmonary embolism
