LAB 5 : Resp Flashcards
How do you read the manometer measuring pressure in the airways and the intrapleural space
You read from the lateral arm, with any reading below zero as negative
How does the magnitude of pressure in the airways change with inspiration and expiration with obstructed vs non obstructed breathing. Why
In non obstructed breathing there isn’t an obvious change in pressure, however in obstructed breathing there is an obvious negative change in inspiration and positive change in expiration. This is because when the airway is narrow it takes longer for air in the atmosphere to enter the airways and equilibrise the pressure in airways with that in the atmosphere.
What 2 forces cause the pressure of the intrapleural space to always be lower
The two opposing forces acting on the membranes:
The collapse of the lungs on the visceral membrane and the springing outward of the chest wall on the parietal membrane. Because of this, the volume of the intrapleural space increases and so pressure will decrease
What is the pressure in the airways vs intrapleural space during inspiration
In airways it is 0 as it is open to atmosphere so can equalise however intrapleural space sealed off so goes subatmospheric
Describe what happens to the lungs/ pressure in the intrapleural space during pneumothorax
The pressure at rest, expiration and inspiration is 0 because intrapleural space is unable to maintain negative pressure gradient. The serous fluid acts as a lubricant and a glue between the membranes but when air enters this space this disrupts the glue.
Compare the intrapleural pressure, content of the intrapleural space (expandable /non) and estimated volume of the space with the lung model vs human
Lung model intrapleural pressure: 0
Real intrapleural pressure : sub atmospheric
Lung model intrapleural content: air (expandable)
Real intrapleural content : serous fluid (not expandable)
Lung model intrapleural volume: 2-3 L
Real intrapleural volume : 2-3 mL
What is peak flow and its units
Peak flow is the maximum expiratory flow rate. This measures the peak pressure difference between the alveoli and atmosphere divided by the resistance of airway.
It is measured in litres per minute
What are the factors that contribute to differences in peak flow rate
gender, age and height
How does peak flow rate of asthmatic compare to normal and why
Expected to be lower because reduced bronchiole diameter-> increased resistance -> can’t have as much volume in same amount of time
How does peak flow rate of young smoker compare to normal and why
Expected to be higher because increased strength of internal intercostal muscles to forcefully expire-> because of increased training through coughing as smoking weakens cillia so they rely on coughing rather than mucocillary escalator to get rid of mucous.
How does peak flow rate of old smoker compare to normal and why
Expected to be much lower because of increased compliance in lungs -> smoking damages elastin which reduces elasticity (recoil force)-> even though inflate easily, Can’t get all the air out and airways more easily collapse, trapping air.
What did the vitalograph (dry spirometer) measure and what do they look like on the graph of volume vs time
Vital capacity (forced vital capacity) shown as the highest point on the graph (often the plateau)
and
Forced expiratory volume in one second shows the volume of air can be forcefully exhaled in one second shown as the volume at 1 s
These can be used to find the FEV1/ FVC ratio which in healthy people is 80%. It can diagnose obstructive lung disease
What is the expected FEV1/FVC of an asthmatic
As airway resistance has increased, the FEV1 will decrease however the VC may decrease due to premature closure of airways but most likely will be comparable to normal, so overall FEV1/FVC is reduced.
What does the Collins spirometer (wet spirometer) measure and what can it not measure
It measures tidal volume, inspiratory reserve volume, expiratory reserve volume. And from these 3, Vital capacity can be calculated.
It cannot measure residual volume so therefore cannot find the total lung capacity
Which has a more accurate FEV : wet or dry spirometer
Dry because the wet is found from an estimation based on nomogram using height
