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104 Cards in this Set
- Front
- Back
Volume inspired/expired with each normal breath:
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Tidal volume
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Vol that can be inspired over and above tidal volume:
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Inspiratory reserve IRV
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Vol that can be expired after expiring TV:
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Expiratory reserve ERV
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Vol that remains after max expiration:
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Residual vol
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What is used during exercise?
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Insp reserve vol IRV
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What can't be measured by spirometry?
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Residual vol
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Anatomic dead space:
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Vol of the conducting airways
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How much is anatomic dead space normally?
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150 mL
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What is Physiologic dead space?
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The volume of the lungs that does not participate in any gas exchange
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What is Phys deadspace equal to in normals?
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Anatomic dead space - normally all the alveoli should be participating!
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What happens to Phys dead space in lung diseases? What kinds of disease?
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It increases - Ventilation/Perfusion defects
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How do you calculate physiologic dead space?
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TV x (Blood Co2 - Exp Co2)
--------------- blood co2 |
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What is Minute ventilation?
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TV x breaths/min
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What is Alveolar ventilation?
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(TV - Deadspace) x Breaths/min
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What is Inspiratory capacity
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IRV + TV
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What is FRC?
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Functional residual capacity
ERV + RV |
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Can you measure ERV w/ spirometry?
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No - cant measure residual vol!
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What is Vital capacity?
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IRV + TV + ERV
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What if you force Vital capacity out?
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FVC - forced vital capacity
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How do you do a FVC measurement?
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By inhaling to maximal and then forcibly expiring
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Can you measure TLC with spirometry?
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Nope - can't measure residual volume with spirometry
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What is FEV1?
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Forced vital capacity in the first second of expiration
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Normally, how much of the forced vital capacity (VC) can be forced out in the 1st sec of breathing out?
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80%
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In what type of lung disease would the FEV1/FVC ratio be DECREASED?
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Disease that obstructs outflow - ASTHMA
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Why is the FEV1/FVC ratio decreased in asthma?
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Bc FEV1 is reduced MORE than FVC - both are reduced, just FEV1 is MORE reduced
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What kind of FEV1/FVC is seen in RESTRICTIVE lung diseases? Why?
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NORMAL or INCREASED - because both FEV1 and FVC are decreased.
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Inspiratory Muscles (which is most important?)
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-Diaphragm - most important
-External intercostals -Accessory muscles |
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When are the external intercostals and acc muscles used?
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Only in exercise
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What muscles are normally used in expiration?
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None - it's normally PASSIVE
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Why is expiration normally passive?
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Because of the lung-chest wall elasticity
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So when are expiratory muscles used?
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In exercise or diseases with increased air resistance like asthma
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What are the expiratory muscles?
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-Abdominal muscles
-Internal intercostals |
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What does COMPLIANCE of the resp system describe?
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The DISTENSIBILITY of the chest wall and lungs
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How is distensibility related to elasticity?
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INVERSELY
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How do we evaluate Compliance?
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By looking at the SLOPE of Vol vs Pressure curve
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What is Hysteresis?
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The difference in compliance curves that are created on the V/P graph during inspiration vs expiration - not the same!
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What is PRESSURE on the VP graph?
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Transmural pressure - the pressure difference across the lung structures
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How is Ptp calculated?
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Ptp = Palv - Pintrapleural
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When is transmural pressure going to increase so you can inhale?
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When intrapleural pressure decreases so that Palv - (-Pip) makes Ptp increase above 0
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And how do you make Pip increase?
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By inhaling with the diaphragm
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What systems are coming into play when we talk about lung compliance?
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-Chest wall
-Lungs |
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How does the combined compliance of the Chest wall + Lungs compare to each alone?
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Combined is LESS than compliance of just the chest wall or lungs alone!
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What 2 forces are equal and opposite at FRC?
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The chest wall expanding out and the lungs collapsing in.
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What pressure is created by these equal/opposing forces?
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Intrapleural pressure
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What is Pip normally at FRC?
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Negative
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What do you suspect if Pip becomes equal to Patm at rest?
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Pneumothorax!
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What is the alveolar pressure at rest?
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Equal to Patm = 0
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How is lung compliance changed in Emphesyma? What is the result?
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It is INCREASED due to loss of elastic tissue in the lungs; the lungs DON'T collapse inward as much so the chest wall EXPANDS
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How does FRC change in emphesyma?
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The lungs seek a new HIGHER frc
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How is lung compliance changed in Fibrosis/restrictive lung diseases?
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It is DECREASED - lungs tend to collapse MORE
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So what happens to FRC in fibrotic disease?
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Lung-chest wall system seeks a new LOWER FRC
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What creates surface tension in alveoli?
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Droplets of liquid on the alveolar surface, btwn which there are attractive forces
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What does surface tension create inside alveoli?
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Collapsing pressure!
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What law describes the collapsing P and how is it calculated?
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Laplace's Law
P = 2T/r |
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So the collapsing pressure is proportional to:
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Directly ppl to Tension
Inversely ppl to alveolar radius |
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What change in alveolar radius will REDUCE collapsing pressure?
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Making alveoli big lowers the collapsing pressure
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So what size of alveoli have a greater tendency to collapse?
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SMALL alveoli
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And how will changes in the surface tension of fluid in the alveoli change collapsing pressure?
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The higher the surface tension, the stronger the tendency of the alveolus to collapse
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How do we get around always having to have LARGE alveoli in order to reduce the tendency to collapse?
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SURFACTANT
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What does surfactant do?
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Reduces surface tension (T) without requiring change in r
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What is it called when small alveoli lack surfactant and tend to collapse as a result?
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Atelectasis
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How does surfactant reduce surface tension?
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By disrupting the intermolecular forces between liquid
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So how does surfactant affect lung compliance?
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It INCREASES lung compliance
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What cells secrete surfactant, and what is it composed of?
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Type II pneumocytes - composed of Dipalmitoyl Phosphatidylcholine
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So, Brian, what is the cause of acute resp distress syndrome in infants?
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Well, I believe it's a failure of type II pneumocytes to secrete dipalmitoyl phosphatidylcholine, resulting in decreased compliance of the lungs!
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When is the earliest secretion of surfactant in the fetus? When should it for sure be secreted?
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Early - week 24 (6 months)
For sure - week 35 (8mo+3wks) |
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So the 3 things that an infant with ARDS will exhibit are:
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-Atelectasis
-Decreased compliance -Hypoxemia |
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What lab msmt indicates adequete and mature levels of surfactant in a fetus?
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L:S ratio - greater than 2:1
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What is the LS ratio?
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Lecithin: Sphingomyelin
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What drives AIRFLOW?
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Pressure differences between the mouth/nose and lung alveoli
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What is the equation for Airflow Q?
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Q = P/R
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What is R?
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The resistance of the airway
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What law describes airway RESISTANCE?
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Poiseuille's
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What is Resistance ppl to directly?
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8 x viscosity x length
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What is Resistance ppl to inversely?
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pi x radius^4!!!
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If the radius of the airways were to decrease by a factor of 4, how would resistance change?
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R would increase by 4^4 - 256!
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What is the major SITE of airway resistance?
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The medium sized bronchi
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How do we change the radius of the med sized bronchi?
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By contracting/relaxing bronchial smooth muscle
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What will constrict bronchial smooth muscle?
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PNS
Irritants SRSA - slow reacting substance of anaphylaxis in asthma |
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What will dilate/relax bronchial smooth muscle?
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SNS
Isoproterenol - B2 agonist |
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Other than radius, what controls airway resistance?
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VOLUME
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How does lung volume alter airway resistance?
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By exerting radial traction
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So what type of lung volume has less vs more airway resistance?
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HIGH vol = LOW resistance
LOW vol = HIGH resistance |
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What would increase vs decrease air viscosity and thus airway resistance to flow?
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Decrease = helium, low density gas
Increase = deep sea dive |
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What is alveolar pressure at the start of a breath before inspiration?
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0 = Patm
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What happens to alveolar pressure during inspiration? After inspiring completely? During expiring? After?
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Inspire - becomes negative
Top of breath - 0 Expire - becomes positive, then back to 0 = Patm |
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What is intrapleural pressure
-At rest -After total inspiration -After expiration |
At rest = -3
Total inspire = -6 After expire = -3 again |
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How can intrapleural pressure be measured?
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With a balloon catheter in the esophagus
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What is lung volume at rest?
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FRC - 40% of tlc
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What is lung volume at the peak of inspiration?
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FRC + TV
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How do we measure lung DYNAMIC compliance?
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By the change in intrapleural pressure during inspiration
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And what causes air to flow during inspiration?
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Pressure GRADIENTS - between Palv and Pip
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What causes air to flow during expiration?
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Positive pressure in the alveoli so that the Ptp gradient is decreased
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When would intrapleural pressure become POSITIVE?
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During a FORCED expiration (not passive breathing)
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What does forcing airflow by increasing Pip actually do?
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Makes expiration more DIFFICULT due to compression of the airways
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What disease shows compensation by learned behaviors to decrease forced resistance to airflow?
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COPD - pink puffer - breathe through pursed lips
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So what disease is characterized by decrease in all lung volumes, but a normal or INCREASED FEV1/FVC ratio?
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Restrictive - Fibrosis
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In asthma what is the:
-FEV1 -FVC -FEV1/FVC ratio -FRC |
FEV1 = very decreased
FVC = decreased Ratio = decreased FRC = increased (can't blow it all out) |
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What is COPD?
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A combination of Emphesyma and chronic bronchitis
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What are the findings in COPD?
-FEV1 -FVC -FEV1/FVC ratio -FRC |
All same as asthma! Obstructive outflow - less expiration
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What is worse; COPD dominated by Emphysema, or by Bronchitis?
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Bronchitis
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How do we differentiate Emphesyma-dom vs Bronchitis-dom COPD?
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Emphesyma = Pink puffer
Bronchitis = Blue bloater |
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Why do we call Bronchitis-dom COPD patients blue bloaters?
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They can't adequetely perfuse, so become severely HYPOXIC, HYPERCAPNIC, and develop Right Ventricular failure, Systemic edema, and are Cyanotic
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What are the findings in Fibrosis?
-FEV1 -FVC -FEV1/FVC ratio -FRC |
FEV1 = decreased some
FVC = markedly reduced FEV1/FVC = N or INCREASED FRC = reduced (fibrosis fills up the space) |