L15 - Respiration 2 Flashcards
Which factors affect airway resistance? What is the main determinant?
length of the system, viscosity of air and diameter of airways
diameter of airways is the main determinant because this factor can be controlled
What is the work of breathing affected by?
airway resistance and lung compliance
What is lung compliance? How does lung compliance affect work of breathing?
lung compliance is the ability of lung to stretch and therefore, decreased lung compliance = increased work of breathing
What is lung elastance?
ability of lung to spring back after being stretched
If lung compliance increases, then lung elastance will also always increase. (true/false)
false
In what cases does lung compliance decrease?
decreases in diseases such as pulmonary fibrosis when inelastic scar tissue is formed
In what cases does lung elastance decrease?
decreases in diseases such as emphysema when elastin fibres in lung are destroyed
How does alveolar surface tension affect lung compliance?
surface tension due to hydrogen bonds between water molecules which resist any force that increases its surface area, thus opposes expansion of alveolus creating surface tension
also, liquid surface area tends to shrink due to attraction between water molecules, thus reducing alveolus size
What is the Law of LaPlace? How does this relate to breathing?
if two bubbles have the same surface tension, the small bubble will have a higher pressure i.e. small alveolus would have increased resistance to stretch and increased work of breathing
What prevents alveoli from collapsing?
surfactant and alveolar interdependence
What is surfactant and how does it affect breathing?
surface active agents which disrupt cohesive forces between water molecules and replace water at the surface (decreases surface tension and resistance of lung to stretch)
How are smaller alveoli able to stretch just as much as larger alveoli?
surfactant is more concentrated in smaller alveoli
What is alveolar interdependence and how does it affect breathing?
alveoli are interconnected so collapsing alveoli stretch surrounding alveoli and when surrounding alveoli recoil this pulls the collapsing alveoli back open
What are two categories of respiratory disease?
obstructive and restrictive lung disease
What is obstructive lung disease? Give some examples.
narrowing of lower airways and increased airway resistance
more difficult to expire
e.g. asthma, emphysema, chronic bronchitis
What is restrictive lung disease? Give some examples.
decrease in lung compliance and increased difficulty of inflating lung
e.g. pulmonary fibrosis
What does a spirometer do?
measures lung volumes and capacities
Do we really know what the residual volume (RV) is? Can we measure it with spirometry?
no, it can only be estimated with spirometry
What can residual volume be measured with?
with a helium dilution method
Why is expiration more affected than inspiration when there is an issue with passage of air?
because we have more muscles dedicated to inspiration
How does obstructive lung disease affect FEV1/FVC ratios?
decreases FEV1/FVC ratios
What is FEV1?
the amount of air breathed out during the first second of forced expiration
What is FVC?
the amount of air breathed out after the fifth second of forced expiration
What is a normal FEV1/FVC ratio?
around 80%
Which one/s of the following will NOT decrease with an obstructive lung disease? (FEV1, FVC, FEV1/FVC ratio, vital capacity, residual volume, total lung capacity, none of the above)
residual volume and total lung capacity
How does obstructive lung disease affect the lungs?
severely reduced FEV1, reduced FVC, reduced FEV1/FVC ratio, reduced vital capacity, increased residual volume, no change in total lung capacity
Which one/s of the following will NOT decrease with a restrictive lung disease? (FEV1, FVC, FEV1/FVC ratio, vital capacity, residual volume, total lung capacity, none of the above)
FEV1/FVC ratio and residual volume
How does restrictive lung disease affect the lungs?
reduced FEV1, reduced FVC, increased or no change in FEV1/FVC ratio, reduced vital capacity, no change in residual volume and reduced total lung capacity
What is anatomic dead space and what is the effect it has upon breathing?
conducting airways known as anatomical dead space e.g. trachea and bronchi
air in conducting airways is not available for gas exchange and therefore we have “wasted” ventilation which affects efficiency of breathing
What is minute ventilation (Ve)?
total ventilation over a fixed time period - usually expressed per minute
How is minute ventilation calculated?
Ve = tidal volume (TV) x frequency of ventilation (f)
What is alveolar ventilation (Va)?
volume of alveolar air (tidal volume minus physiological dead space) exchanged per unit time
Is there a ‘functional’ difference between TV of 0.15L / f = 40 and TV of 1.20L / f = 5?
yes, there is a big difference because in the first situation we are only exchanging the anatomic dead space
