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26 Cards in this Set

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  • Back
How many generations does the bifuraction pattern go through? How does the diameter of the airway change through bifurcation?
*23 generations
*diameter decreases from 25mm to 0.25mm
What is the action of the diaphragm in inspiration? What percentage of the change in volume of the thoracic cavity is accounted for by the action of this muscle?
*as it contracts the volume of the thoracic cavity is increased
*accounts for 85% of the volume change
Contraction of the external intercostals produces what kind of action? When is this used?
*contraction lifts the ribs upwards and outwards to increase the volume of the thoracic cavity
*used during active inspiration
During normal tidal breathing, expiration is an active process.
False: it is a passive process.
What muscles are used to effect active expiration?
*abdominal muscles
*internal intercostals
What is alveolar pressure at end expiration? What is air flow at this point?
*alveolar pressure is zero
*there is no air flow
Where is the intrapleural space located? How much fluid in contained in this space?
*between the outer covering of the lungs and the inner covering of the ribs
*contains ~2mL of fluid
What is IPP at end expiration? What produces this pressure?
*-5 cmH2O
*produced by the tendency of the lungs to collapse and the tendency of the ribs to spring outward
What is IPP during inspiration? What causes this change? How does this affect alveolar pressure?
*IPP become -8
*an increase in the volume of the thoracic cavity causes this
*alveolar pressure becomes -1
What is transmural pressure? How can it be calculated?
*the pressure across the alveolar wall or respiratory membrane
*equal to alveolar pressure minus IPP
What is transmural pressure at end expiration? During inspiration?
*end expiration: 0 - (-5) = +5
*inspiration: (-1) - (-8) = +7
At what point of the respiratory cycle does alveolar pressure reach its peak? IPP?
*alveolar pressure peaks at mid-inspiration
*IPP peaks at the end of inspiration
Expiration takes twice as long as inspiration during normal tidal breathing.
This is true and is due to the fact that expiration is a passive process.
What is a pneumothorax? How can it be caused? What effects does it have?
*the entry of air into the IP space, thus disrupting the pressure gradient
*trauma (from the outside) or infection (from the inside)
*disruption of the pressure gradient causes lung collapse
What is tidal volume? What is a normal value?
*the air moved in and out of the lung during normal breathing
*0.5-1 L
Give the series of events that leads to development of subatmospheric alveolar pressure.
1. Inspiratory muscles contract
2. Thoracic cavity expands
3. IPP becomes more negative
4. Transmural pressure increases
5. Alveolar pressure becomes more negative and air enters.
What is the inspiratory reserve volume? The inspiratory capacity?
*IRV = amount of air that can be inspired past tidal volume
*IC = TV + IRV
What is expiratory reserve volume?
The amount of air that can be expired past tidal volume.
What is vital capacity? How can it be calculated?
*the maximum volume of gas that can be forcibly expired after maximal inspiration
*VC = IRC + TV + ERV
What is residual volume?
The amount of air left in the lungs after forcible expiration (i.e. after ERV has been reached)
What is functional residual capacity? How can it be calculated?
*volume remaining in the lungs after tidal expiration
What is total lung capacity? How can it be calculated? What is a normal value?
*the total volume of the lungs from maximum inspiration to residual volume
*TLC = RV + ERV + TV + IRV
*6L for 70-kg person
What are two methods of measuring residual volume?
1. Helium inspiration method (inaccurate for patients with obstructed airways)
2. Body plethysmograph
What changes in lung volumes can be expected in patients with obstructive lung disease?
*FRC and RV are increased
*VC is decreased
*TLC may increase in chronic conditions
What changes in lung volumes can be expected in patients with fibrotic restrictive lung disease?
A decrease in TLC, FRC, and RV
What changes can be expected in patients experiencing restrictive lung function due to obesity?
*TLC and RV remain constant
*FRC decreases