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30 Cards in this Set
- Front
- Back
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What are the pressures measured relative to?
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Atmospheric pressure
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What is the ideal gas law and what does it apply to?
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Dry gas
PV=nRT Pa m(^3) J.K(^-1).mol(^-1) K |
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At a constant temperature and volume, pressure is proportional to
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number of moles
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What is a partial pressure?
What does it depend on? |
The pressure exerted by each individual gas
number of moles in the given volume + temp |
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Which gradients do convection and diffusion travel down?
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bulk + partial pressure gradient
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What is Dalton's law?
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Each gas in adry mixture exerts a partial pressure proportional to its fractional share of the share of the total volume
Pgas = Fgas x total pressure |
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What is the effect of altitude on barometric pressure?
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halves every 5450m
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What is the effect of altitude on Pgas?
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lowers it
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What are STPD and BTPS?
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standard temp (O celcius) pressue (101kPa) dry
body temp (37 celcius) pressure (101kPa) saturated |
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To calculate the dry mixture, what must be done to the pressure of the saturated gas?
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PH2O must be subtracted from the total volume
so at BPS = Pgas = Fgas x (barometric pressure - PH2O) |
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What is the value of intrapleural fluid?
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only a few ml
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What state is the pleura in?
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Virtual contact - virtually no space between the space
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How many pleural sacs are there?
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2, one for R and one for L lung
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Where can we measure pressures?
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outside the chest wall (Patm/PB)
between the pleural membrans (Ppl) inside the alveoli (PA) inside the airways (Paw) |
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When there is no airway, what is the value of PA?
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0
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What is the value of intrapleural pressure when there is no airway?
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negative
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How do you work out transmural/distending pressures?
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Pin - Pout
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What does a positive distending pressure mean?
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It's filling/getting larger
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At FRC, the lungs are
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partially inflated
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Why are the lungs partially inflated at FRC?
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equilibrium between alveoli (want to collapse/is partially inflated) and chest wall (wants to expand/is partially compressed)
lung distending pressure: PA - Ppl = o - -1 = +1 chest wall distending pressure : Ppl - PB = -1- 0 = -1 |
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What happens in a pneumothorax?
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pressures equilibrate
chest wall expands Ppl = PB = 0 lung collapses PA = Ppl = 0 |
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What is responsible for inspiration?
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Respiratory muscles
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What is responsible for passive expiration?
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elastic recoil
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What is Boyle's law?
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At constant temperature and number of moles, pressure is inversely proportional to volume
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Where is the diaphragm located?
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C3-C5
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What does the diaphragm do?
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Lengthens (front to back and side to side) the thoracic cavity by contracting
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Where are the external intercostal muscles?
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T1-T11
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What do the external intercostals do?
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Expand the ribcage: +
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What is the sequence of events for quiet inspiration?
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thorax expands
Ppl falls Lung distending pressure increases Lungs expand PA falls below PB Air flows into lungs exact opposite for expiration |
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What 2 factors must be overcome to allow inspiration to happen?
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stretching of the elastic components of the respiratory system (15%)
overcoming the resistance to airflow (85%) |
