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70 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What makes up the ventilatory apparatus?
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The lungs and the surrounding chest wall
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What does the chest wall consist of?
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Rib cage
Diaphragm Abdominal wall |
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Where are the visceral and parietal pleura located?
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Visceral: Lungs
Parietal: Chest wall |
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Are the lungs attached to the chest wall?
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No, but they act in series with the chest wall
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Why is there negative P?
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Chest always want to pull out, lungs always want to collapse in
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How are the visceral and parietal pleura coupled together?
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By a thin layer of liquid that fills the intrapleural space
->The liquid lets the lungs slide against theinternal wall of the chest during breathing and to follow the change in thoracic configuration |
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What is Pleural Pressure (Ppl)?
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The P that can be measured in the liquid filled spcae between the lungs and chest
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What i the Ppl at rest? Why?
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Negative
Due to the opposing forces acting on the lungs and chest wall |
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What happens if there's a pneumothorax?
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The lungs collapse and the chest springs outwards
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How can the elastic properties of the respiratory system be measured?
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Measure the changes in the recoil pressure of the different structures for a given change of lung volume
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How can lung volumes be mesured?
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Spirometry
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What is used to measure respiratory system P?
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Manometers
Pressure Transducers (they're referenced to atmospheric pressure) |
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What is recoil pressure?
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Pressure difference between the inside and the outside of the structure (transmural P)
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What is negative P?
Positive P? |
Negative: P below atm
Positive: P above atm |
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What is the recoil P of the chest wall, transchest-wall P (Pw)?
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Difference between Ppl and the P at the body surface
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How can Ppl be measured?
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Using a ballon introduced into the esophagus
->esophagus is between 2 pleural spaces so esophageal P is a close approximation to pleural P |
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What does Pw (chest wall) equal?
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Pw = Ppl - Pbs
bs:body surface pl: pleural w:chest wall |
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What is the recoil P of the lungs?
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Transpulmonary P (Pl)
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How is Pl measured?
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Pl = Palv - Ppl
->if no air flow, closed nose and mouth, P alv and P at the mouth are the same |
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How is the recoil P of the total respiratory system , the transrespiraoty system P (Prs) measured?
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Difference between Palv and Pbs
Prs = Palv- Pbs -> Palv = Pl + Ppl -> Pbs = Ppl - Pw .: Prs = Pl + Pw |
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What does compliance of the lungs/chest wall/total respiratory system refer to?
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Ease with which each of these structures can be distended
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How is the respiratory system compliance determined?
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Determne the static P-V relationship while lung volume is decreased step by step from TLC
(C= dV/dP) |
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What happens to P to maintain a given volume of gas in the lungs if the volumes increase?
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P must also increase
(slope of P-V curve decreases with increasing volume) |
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In which diseases is lung compliance altered?
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Emphysema
Fibrosis |
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What does the P difference between the alveoli (Palv) and the pleural space(Ppl) equal?
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P drop across the lungs
->P req'd to maintain the lungs at a given inflation volume against their tendency to recoil Cl = dV/ (dPalv-dPpl) |
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How is lung compliance (Cl) related to elastcity (El)?
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El = 1/Cl
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How is the elastic recoil of the lungs produced?
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Partly by elastic lung tissue
Mostly from properties of the liquid film lining the inside of the lungs |
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Why does the surface tension of this liquid film generate such a force?
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The SA of the film is so large
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What happens during fibrosis?
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Deposition of fibrotic tissues on alveol surface (makes them stiffer, harder to inflate then the alveoli)
Get smaller change in V for a given P |
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What happens in emphysema?
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Destruction of the alveolar wall
->Easy to inflate them but not easy to recoil, hard to deflate the alveolu ->FRC will we higher than normal Need to use moe expiratory muscles, but still have a higher volume |
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What happens to the lungs at higher volumes?
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Harder to stretch the lungs
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Is compliance measurement static or dynamic?
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Static
->Fill lungs then take a measurement |
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Why is the P when measuring the lung compliance always positive?
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Lungs always tend to collapse
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How come the compliance P for the chest wall can be positive and negative?
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Chest wall tends to collapse only after reaching a volume of 60% vital capacity
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What happens when the chest is compressed?
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It wants to spring out
-> Negative P |
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What happens when cest P is increased?
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It will want to collapse: Positive P
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What is the Prs (P drop across the respiratory systm) at FRC?
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Zero, because the system is at rest
->stable condition caused by the inward recoil of the lungs (+5cm H2O) which is balanced by the outward recoil of the chest (-5cm H2O) ->At FRC, the lungs are above their resting volume and th echest is below its resting volume (**Pneumothorax**) |
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What happens during a pneumothorax?
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Air enters the pleural space cuz Ppl < Patm
Lungs collapse to their resting position below RV Chest wall expands towars its resting position (~75% of total lung capacity) |
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Why can a spontaneous/traumatic poneumothorax be life-threatening?
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Lungs are uncoupled from the chest wall
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What happens during inspiration?
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Diaphragm contracts and the chest wall is pulled open
->Get a more negative Ppl that cause chest expansion |
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What happens if the chest volume is increased?
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The Ppl is decreased (P becomes more negative)
->Lungs will follow: inflate lungs, decompress air in the lungs |
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Is Palv or Patm greater during inspiration? Expiration?
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Inspiration: Palv < Patm
Expiration: Palv > P atm |
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What is the equation for flow?
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F= (Palv-Patm)/R
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What happens as the lungs are pulled further and further away from their resting position (which is below Residual volume)?
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Ppl becomes more subatmospheric
As lung volume increases, gas in the lungs are decompressed Palv drops below atmospheric P This produces neg P gradient btw the alveoli and atm makes air flow to the lungs |
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What happens as inspiration continues?
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Lungs fill up with air
P gradient and air flow start to decrease At the end of inspiration, airflow stops because Palv=Patm |
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What happens at the onset of expiration?
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Diaphragm relaxes
Elastic recoil of the respiratory system compresses the gas in the lungs Palv increases Positive P gradient btw the atm and lungs is reversed and air from the lungs to the atm |
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What happens near the end of expiration?
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Lung volume decreases
Ppl slowly returns to its resting level At the end of expiration (FRC), air flow= 0ml/s and Palv=O cm H2O and Ppl= -5cm H2O |
Look at SLIDE for DYNAMICS of breath
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What is required to get airflow through the airways?
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P of airway opening (Pao) must be different to that in the alveoli (Palv)
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What is the resistance of the airways to gas flow (Raw)?
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Ratio of Pao to Palv difference and the flow
Raw= (Palv-Pao)/Flow |
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What has more resistance, a large diameter or small diameter?
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Small diameter
**Air resistance is related to airway caliber and is an important determinant of lung fuction** |
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What happens in asthma?
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Lumen becomes smaller
Diameter of airway decreases .: less air can come in per unit of time |
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Why is the descending portionof the flow-volume curve independent of effort?
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Because of the compression of the airways by intrathoracic P
**Pleural P is greater than airway P** |
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What happens to the P's before, during and end of inspiration and then during forced expiration?
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Before: Airway P=0 and Intrapleral P= -5cm H2O
During: Pleural an airway P fall End: Airway P =0 and airway transmural P = 8cm H2O Forced expiration: Intra-pleural and alveolar P are increased ->because of the P drop along the airways as flow begins, there is a point at which there is a positive P tending to close airways |
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What is an example of a restrictive disease?
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Fibrosis
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What is an example of an obstructive disease?
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Emphysema
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What happens in restrictive diseases?
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Max flow rate and max volume exhaled are reduced
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Wha happens in obstructive diseases?
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Flow rate is very low and a scooped out appearance is often seen
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What happens to the lungs in restrictive diseases?
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Lungs very stiff
Lungs want to recoil so flow will be greater for a given lung volume, but lower if compared overall) |
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What happens to the lungs in an obstructive disease?
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Lungs easier to inflate
Hard for lungs to recoil For any lung volume, flow < normal |
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What is an important contributor to the mechanical properties of the respiratory system?
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The surface tension of the liquid film lining the lungs
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How oes this surface tension arise?
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The molecules in the surface of the film tend to arrange themselves in the configuration that has the lowest energy
->they're mmore attracted to themselves then air molec ->generates tension across the film surface |
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When can this tension produce a pressure?
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If the surface is curved
->inside n alveolus or airway |
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What is La Place's law?
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P= 4T/r
(P is inversely proportional to the radius, .: the P inside a smaller bubble is greater than inside a large bubble) |
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What happens to the surfactant that is secreted by epithelial cells?
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It puts itself between water molecules and decreases the surface tension
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What is the difference in surfactant in small alveoli and large alveoli?
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Many small alveoli: have many layers of surfactant
->decreases surface tension a lot 1 Large alveoli: only has 1 monolayer of surfactant ->Surface Tension decreases by less |
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What would happen if we didn't have surfactant? Why?
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We wouldn't be able to breathe because the forces of surface tension are so great
(surfactant stabilizes the lungs, but produces more of an effect in small alveoli than large ones) |
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What prevents the collapse of small alveoli into larger ones?
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Pulmonary surfactant
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Which cells secrete pulmonary surfactant?
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Alveolar type II cells
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What are the 2 principle roles of pulmonary surfactant?
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1) Make surface tension in the alveoli change with lung volume to prevent the P in the small alveoli fom exceeding the P in the large alveoli
2) Reduce overall surface tension so that we can breathe |
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What would happen if the surface tension in the liquid lining layer was the equal to that of water?
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We wouldn't be able to inflate our lungs
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