Respiratory Module 1 Flashcards
What is ventilation and how is it measured
the removal of CO2 from the lungs. measured by PaCO2 or PvCO2
What is oxygenation and how is it measured
The movement of oxygen through the blood. Depends on the integrity of the exchange interface and the surface area available. Measured through PaO2
What is partial pressure
This is the pressure exerted by a gas dissolved in a liquid
What is compliance, what is the compliance of a normal lung?
The distensibility of lungs. The normal lung has high compliance meaning it distends easily with minimal pressure
What compromises the ventilatory apparatus and what does it do
chest wall, diaphragm, nerve and blood supplies. Moves the air in and out of the lungs
Pulmonary parenchyma is made up of…
Alveoli, lymphatics, blood supply and interstitium
What is the conducting zone
regions of the lower respiratory tract that conduct air and take no part in gas exchange. This area holds a fixed amount of air and is referred to as the anatomic dead space
What is the respiratory zone
after the terminal bronchioles the respiratory bronchioles start and they take part in gas exchange. Gas movement occurs through diffusion as there is no velocity present due to the large surface area
How is the lung ventilation and perfusion spread
Ventilation: alveoli dorsally are larger than those ventrally as the weight of the lung compresses the more ventral alveoli. Ventral alveoli have a greater capacity to expand.
Perfusion: there is greater perfusion ventrally due to gravity pulling blood
What cells are the alveolar epithelium made of
Alveolar epithelium is made of Type 1 and Type 2 pneumocytes. Type 1 cells are large flat epithelial cells and make up 95% and Type 2 cells are taller and bigger cells that produce surfactant
What stimulates breathing
- Hypercarbia - very tightly managed
- Central Chemoreceptors: located in the ventral medulla, sensitive to changes with pH and will increase ventilation to decrease this. CO2 –> BBB –> reacts with H2O to form H+ and HCO3 in CSF and alters pH
- Pulmonary stretch receptors: mechano-receptors located in the airway of smooth muscle - slow respiration in response to pulmonary distention
- Peripheral chemoreceptors: Located in the carotid bodies and aortic bodies - activated by low PO2 (hypoxaemia) and decreased pH - PaO2 has to be quite bad to trigger - O2 sensitive k+ channels
Explain the normal respiratory cycle
Normal cycle has active inspiration and passive expiration. External intercostal muscles contract to pull out rib cage and the diaphragm contracts and flattens to allow expansion. All this causes the chest cavity to expand causing an increase in negative pressure that pulls air in through the nostrils
Expiration occurs passively due to natural recoil of the lungs when the external intercostal muscles and diaphragm relax in to resting
Explain residual volume and its role
the amount of air left in the lungs after maximum expiration. This prevents alveoli from completely collapsing and would lead to shear injury of the alveoli
what makes up the total lung capacity
Residual volume and the vital capacity
Explain the ventilation perfusion zones that are possible within the lungs
Three zones.
Zone 1: highest V/Q - the capillaries are squashed by the alveolar pressure so there is minimal to no blood flow with good ventilation - not present in healthy animals
Zone 2: Central region of lungs - pressure in the arterial capillaries are higher than alveolar pressure allowing perfusion to occur but is dependent on the arterial-alveolar pressure gradient (finger on hose pipe)
Zone 3: Blood flow exceeds the ventilation. the most dependant part of the lung
