L3- Why do we breath Flashcards
How much oxygen does an adult normally consume and how much carbon dioxide does that produce?
VO2- 1000ml/O2/min
VCO2- 800ml/CO2/min
What are the functions of the lungs
- Gas exchange
- Defensive
- Metabolic
- Endocrine
- Haemotologic
- Immunologicon
- thermoregulatory
- water-eliminative
- phonati
Define the Respiratory quotient
THe lungs must accomodate up to 30 fold increase in gas transfer. Explain why this is the case
exchange of gases must occur in accordance to increase in metabolism. Any failure to do so will result in a mismatch between ventilation and metabolism- respiratory dysfunction with associated increased morbidity and mortality
How many generations are there in the bronchiole tree.
What are the names
What are the conducting zones and respiratory zones
- Diameter decreases and cross sectional area increases down the bronchial tree
- Conducting zone- first 16 bifurciations
- too thick for gas exchange
- convection- bring air in and out
- O2 and CO2 concentration vary a lot during breathing
- Respiratory zone
- thinner- gas exchange
- O2 and CO2 concentration vary little due to slow movement in diffusion
How does the tidal flow of gas in the terminal bronchioles - and beyond - differ from the tidal flow of gas at the trachea?
- gas speed decreases as the generation number increases
- this is because the flow remain constant and the area increases down the bronchial tree
What is the relationship between airway generation and area?
- little increase from 0 -16. tremendous increase from generation 17 onwards
- exponential
What is the diffusion of gases dependent upon?
- partial pressure gradient
What is meant by the term Barometric pressure PB?
- the pressure exerted by the weight of gas molecules in the atmosphere above the point of measure
- at sea level, atmospheric pressure is about 100 kPa
- decreases exponentially with altitude
What is the partial pressure of a gas?
- The pressure of of any particular gas, whether alone or in a mixture with other gases
- depends upon the number of molecules of that gas in the given volume and on the temperature
- Dalton’s Law of partial pressure
- Total pressure = P1 + P2 + P3 +… Pn, where P is the partial pressure of an
individual gas
- Total pressure = P1 + P2 + P3 +… Pn, where P is the partial pressure of an
- Partial pressure= fractional concentration of a gas in mixture x total pressure
What is meant by dead space?
- the volume of gas within the respiratory systems in which gas exchange does not occur
- consists of anatomical dead space and alveolar dead space
-
Anatomical dead space
- conducting zone
- Alveolar dead space
- volume of alveolu in the Respiratory zone where gas exchange should but does not occur
What are the factors that affect dead space?
- Anatomical Dead Space
- size of object- larger the person, larger the anatomical dead space
- Alveolar dead space
- alveolar dead space is normally too small to be measured. It is increased significantly in certain lung diseases
- this is primarily due to under perfusion to affected alveoli ( reduction in blood flow)
- pulmonary hypotension due to haemorrhagic blood loss or pulmonary embolism
- this will decrease alveolar ventilation and therefore impact adversely upon blood oxygenation, CO2 and pH
Define Minute/Total ventilation
- volume of gas breathed out in one minute
- tidal volume x respiratory frequency
- 500ml x 12 breaths/min = 6.0L/min
Why does total ventilation not equal to alveolar ventilation
- presence of dead space volume VD
- not all of total ventilation reaches the Respiratory Zone and therefore not all of it is useful for gas exchange
Define Alveolar ventilation.
- the ‘useful’ componenet of total ventilation in terms of gas exchange
- can be affected by changes in physiological dead space and the pattern of breathing
