L29. Ventilation and Perfusion Flashcards
Describe what is meant by ventilation.
Air moving in and out of the lungs
Describe what is meant by perfusion
deoxygenated blood moving into the lungs and becoming oxygenated
What is the V/Q ratio?
When P O2 and P CO2 levels are maintained by ventilation and perfusion
Are alveoli in the apex or base more expanded? Why
Apex due to gravity
What is compliance? What does high compliance mean? Give an example of where you would see reduced compliance.
How much effort is required to stretch the lung wall.
High compliance = easily
Decreased compliance = pulmonary condition
What is anatomical dead space?
the total volume of the conducting airways
What is physiological dead space?
The total volume what doesn’t participate in gas exchange
Name the 2 types of blood circulation.
- pulmonary circulation - brings deoxygenated blood from heart to lungs, and oxygenated blood from lungs to heart.
- Bronchial circulation - brings oxygenated blood to the alveoli
Describe the pressures of systemic and pulmonary circulation.
Systemic : high pressure, high resistance
Pulmonary : low pressure, low resistance
What is arterial hypoxemia?
When arterial P O2 is less than 80mmHg
Give the values for Hypoxia.
P O2 is less than 60mmHg
Give the values for hypercapnia
P CO2 is greater than 40mmHg
Give the values for hypocapnia
P CO2 is less than 35mmHg
Describe an anatomical shunt.
When mixed venous blood is “shunted” into arterial blood.
What is a right to left shunt? Where do shunts often take place?
blood being shunted (added) is deoxygenated.
In the heart - right atrium/ventricle blood crosses the septum into the left atrium/ventricle.
What is a physiological shunt?
When blood in non-ventilated alveoli (deoxygenated) is mixed with oxygenated blood.
What is atelectasis?
obstruction of ventilation due to mucous plugs
What is happening when V/Q = 0?
no ventilation to one area = choking
What is happening when V/Q is low?
asthma
What is happening when V/Q = infinity?
no blood flow eg pulmonary embolism
What is happening when V/Q is high?
decreased gas exchange eg pulmonary fibrosis
What is COPD and what does it mean?
Chronic obstructive pulmonary disease
airflow is obstructed (long term smoking)
What are the causes of Emphysema?
Low elastic recoil - inhalation is easy, exhalation is hard
What is chronic bronchitis?
Inflammation of bronchi
