Matching lung ventilation and perfusion Flashcards
(27 cards)
What does perfusion mean?
Blood flow through any organ
What is the regional difference in size of alveoli?
Apical alveoli are 4X larger than basal alveoli - due to gravity
What is the regional difference in ventilation?
Apical (towards the top) - lungs have better ventilation due to gravity.
Which region alveoli expands better?
Basal region expand more than apical alveoli
What is the cardiac output to the lungs?
Full cardiac output but at a very low pressure compared to the systemic circulation.
How many divisions of airways is there before a major airway becomes an alveolus?
23
First 16 = conducting
Last 7 = respiratory
What does emphysema do?
Destruction and dilatation of distal airway - causes regional destruction of vascular beds and poor gas exchange = hypoxia.
What is hydrostatic pressure?
Force exerted by weight of a fluid (blood/water) due to gravity.
What can regional differences in lung perfusion be demonstrated by?
STARLING’S RESISTOR
What is alveolar dead space?
Good ventilation but no perfusion
Which zone is alveolar dead space?
Zone 1
Why is there poor blood flow in zone 1?
Lung apex is 15cm above right ventricle - very high up - gravity.
Also very small area in healthy people
What are the pressures in zone 1?
P alveolar > P arterial > P venous
P alveolar = PA
P arterial = Pa
P venous = Pv
.
What is the V/Q ratio in zone 1?
Very high
What is the pressures for zone 2?
Pa > PA > Pv
In zone 1, Blood flow is determined by the difference in?
PAlveolar & Parterial (first two words)
What happens in zone 3?
Very good perfusion due to high hydrostatic pressure (gravity causes blood to flow downwards) and also very good ventilation because lungs have greater capacity to expand at the bottom
What is the pressures in zone 3?
Pa > Pv > PA
If the amount of ventilation to an area is equal to the amount of perfusion then the ratio of V/Q is …….
1
What is anatomic dead space?
dead space is the volume of air which is inhaled that does not take part in the gas exchange, either because it (1) remains in the conducting airways, or (2) reaches alveoli that are not perfused or poorly perfuse
What is the significance of pulmonary embolism?
certain groups of patients have higher chances of DVTs, clots can get dislodged and travel to the lung blocking major vessels. Severe hypoxia; lack of blood supply to that part of the lung
What is the equation of physiological dead space?
Physiological dead space = anatomical dead space + alveolar dead space
i.e part of each breath that does not take part in gas exchange
What is a shunt?
deoxygenated blood reaching left side of the heart either bypassing lungs or failing to get oxygenated in the lungs; Examples include bronchial veins, pnenumothorax, age related changes: areas low V/Q ratio in the lungs Minimal effect of oxygen supplementation on a very large shunt.
