Ventilation + Perfusion matching Flashcards
(21 cards)
define ventilation
-process by which oxygen and carbon dioxide are transported in and out of the lungs (breathing)
define perfusion
-blood flow through a region eg. capillary network around lungs
define gas exchange
-process by which oxygen and carbon dioxide diffuse across the alveolar-capillary membrane
define impaired gas exchange
-excessive or insufficient diffusion of oxygen and/or carbon dioxide across the alveolar-capillary membrane
how does optimal V/Q matching occur
-ventilation and perfusion need tobeoptimallyinthe same place at the same time foroptimalgaseous exchange
-we can use positioning to influence V/Q matching
where is perfusion greater?
-upright sitting perfusion is greatest in the lower lobes of the lungdue to gravity
describe the transport pathway
AIRWAY/ LUNGS- HEART- TISSUE
-O2 transport travels through the bronchioles to the respiratory bronchioles and alveoli where it diffuses across the single membrane (easier for gas exchange) to the capillaries
-taken to the left side of the heart (atrium) via the pulmonary vein and then goes off to the body where required where its used by the mitochondria
CO2 in transport pathway
-the opposite as it’s a waste product from cells/organs etc., transported by the blood via the heart to the lungs, diffuses into alveoli and is exhaled
how can you maximize the transport pathway?
-influenced by positioning & mobilization
how can the transport pathway be affected?
-compromised by disease, surgery and immobility
what is perfusion?
-the process of blood flow through the body’s network of capillaries to nourish and maintain the health of tissues and organs
what is the slinky effect?
(detailed)
-at the end of normal expiration: alveoli in apex of lung aremore expanded than the base, however alveoli in base of lungs has more potential to expand
during inspiration air quickly fills the alveoli apex of lung to capacity, then flows down to bases meaning alveoli in the bases fill with more air than the apex
-therefore ventilationis greatest in the lower lobes
-only applies during standing or sitting upright
describe how the rate of ventilation changes through the areas of the lungs?
-upright posture, lung apices (non-dependentarea) have agreater initial volume but reduced compliance(ability to stretch)
what is a shunt?
reduced blood flow causes no/reduced ventilation
what causes shunt?
-airway disease (COPD)
-pleural effusion
-atelectasis
what is dead space ventilation?
ventilation causes no/ reduced blood flow
causes of dead space?
-PE
-fibrosis
-heart failure
where is ventilation and perfusion match?
-lower lobes - when in upright position
what happens to ventilation in a supine position ?
-anterior aspect of lung alveoli overinflated
-posterior aspect of alveoli are atelectatic
2 causes of impaired gas exchange
-reduced FRC
-V/Q mismatch
define functional residual capacity
-volume of gas remaining in the lungs at the end of a normal tidal exhalation & the point at which lung recoil and chest wall recoil are equal
