respiration VQ relationship Flashcards
what is ventilation?
process by which air moves in and out of the lungs
what is perfusion?
process by which deoxygenated blood passes through lungs and becomes oxygenated
what is the V/Q ratio?
Major determinant of normal gas exchange and thus the level of PO2 and PCO2 in blood is the relationship between ventilation and perfusion.
what causes ventilation to not be uniformly distributed in the lung?
gravity
what part of the lung is more expanded in the upright position?
alveoli in apex
is pleural pressure more negative at the apex or base?
apex
is transpulmonary pressure greater at the apex or base?
apex
what is compliance?
how much effort is required to stretch the lungs and chest wall
what does high compliance mean?
lungs and chest wall expand easily
what are common pulmonary conditions in which decreased compliance is common?
Scarring in lung tissue (tuberculosis)
Lung filled with fluid (edema)
Deficiency in surfactant production
Destruction of elastic fibres (emphysema
what is resistance?
any narrowing or obstruction of the airway that may reduce airflow
what pulmonary conditions is increased resistance common?
Asthma
COPD (emphysema, chronic bronchitis) due to obstruction or collapse of airways.
what are the two types of dead space?
anatomical and physiological
what is anatomical dead space?
volume of gas during each breath that fills the conducting airways
what is physiological dead space?
Total volume of gas in each breath that does not participate in gas exchange, e.g., alveoli that are perfused but not ventilated.
what are the two blood supplies of the lungs?
pulmonary and bronchial
what is the pulmonary blood supply of the lungs?
brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart.
what is the bronchial circulation of the lungs?
brings oxygenated blood to lung parenchyma
which circulation system is more influenced by gravity?
pulmonary (low pressure low resistance)
what is the V/Q ratio in a single alveolus defined as?
alveolar ventilation divided by capillary flow
what is the V/Q ratio in a lung defined as?
total alveolar ventilation divided by cardiac output
when is V/Q >1?
ventilation exceeds perfusion
when is V/Q <1?
perfusion exceeds ventilation
apical vs base lung V/Q
what is an anatomical shunt?
Mixed venous blood ‘shunted’ directly into arterial blood.
(incase of lung – mixed pulmonary artery blood shunted into pulmonary veins)
what does a right to left anatomical shunt lead to?
dilute amount of oxygen circulating body
what is a physiological shunt?
alveolar sacs aren’t ventilated due to blockage
what is atelectasis?
obstruction of ventilation due to mucous plugs, airway oedema, foreign bodies, tumours in airways
what is COPD?
chronic obstructive pulmonary disease
- condition in which airflow is obstructed
- encompases emphysema and chronic bronchitis
- most common in long term smokers
- chronic cough, tight chest, shortness of breath, increased mucous production
what is emphysema>
- Structures in alveoli over inflated.
- Lungs loose elasticity, cannot fully expand and contract.
- Patients can inhale but exhalation is difficult due to decreased elastic recoil.
what is chronic bronchitis?
- Inflammation of bronchi causing mucous production and excessive swelling.
- Shortness of breath with mild exertion.
- Chest infections more prevalent.
- difficult for air to get into the lung
what is pulmonary fibrosis?
- A type of interstitial lung disease.
- Scarring and thickening of tissue.
- Decreased elasticity.
- Decreased gas exchange.
- patient diagnosed will normally die within 4 years
