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86 Cards in this Set
- Front
- Back
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Why aren't the lungs completely filled during inspiration and emptied during expiration under normal resting conditions?
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It's inefficient
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What is residual volume?
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The volume that will always be left in the lungs no matter how hard you try to blow it out.
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What is the approximate value of RV in most people?
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1.1 liters, 20-25% TLC
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What is Vital Capacity?
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TLC minus RV
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What is Tidal volume?
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the amt of air you normally take in - about 500 mL
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What is FRC - functional residual capacity?
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The amt of air left in the lungs at the end of a normal breath; RV + ERV = 40%TLC
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2 Reasons why we can't exhale completely:
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1. The chest wall can't contract all the way
2. The airway will collapse long before the alveoli will |
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What is required in order to reach FRC?
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Nothing; no muscle activity, just passive expiration.
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What is reached when expiratory muscle activity is maximal?
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Residual volume
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What % of TLC is:
-FRC -RV |
FRC = 40% TLC
RV = 20% TLC |
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Does the same amount of air that is inspired during normal breathing equal that which reaches the alveoli? Why/why not?
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No; because the first air that reaches the lungs during inspiration is the same air that just left the lungs
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What do we call that air that first reaches the alveoli during inspiration?
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Dead space volume
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What is Ve?
(w/ a dot over it) |
Air expired - the total amt of air exiting the lungs in one minute
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What is Vi?
(w/ a dot over it) |
Total amount of air reaching the lungs in one minute
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What is Vd?
(w/ a dot over it) |
Dead space volume - the volume of airways.
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What is VA?
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Volume of fresh atmospheric air reaching the alveoli/lungs per minute
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What is Va equivalent to?
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Ve - Vd
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How do you calculate Ve, Vi, or Vd?
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That volume x frequency
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Are Ve and Vi always equivalent?
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No; if you're burning pure glucose they are, but normally they're not exactly equal.
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What is the normal ratio of Ve:Vi?
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10:8
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What does a spirometer measure?
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The fractional percentage of O2 and CO2 at the mouth during inspiration and expiration.
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What happens to the composition of expired air as airflow changes?
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Composition changes when breathing flow rate changes.
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How does air composition change when you exhale more quickly?
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%CO2 increases
%O2 decreases |
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Define dead space volume:
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The air in the conducting airways that did not reach the alveoli during inspiration; first air to reach them next time.
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What is the dead space air composition?
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Same as that of atmospheric air
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When you increase the flowrate of expiration what is the final peak PCo2 and nadir PO2 levels after time? what are normals?
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PO2 = 13.5% (vs 15.5% normal)
PCo2 = 6.4% (vs 5.5% normal) |
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What happens to the air composition during normal breathing (not changeing flowrate)?
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It also changes
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What is the initial air exhaled?
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Dead space air - same in comp as atmospheric air.
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What happens to expirate after all the dead space air is cleared out of the lungs?
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The gas levels become the same as alveolar levels - higher CO2 and lower O2
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How are end tidal PO2 and PCO2 levels useful?
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Allow us to estimate alveolar and arterial blood gas levels b/c once gas exchange has occurred PCO2 is identical in these values - BUT NOT PO2!!
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How does the PO2 value differ in alveolar vs arterial blood?
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Alveolar O2 is 6 mm Hg higher than arterial PO2
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Formula for estimating partial pressure of a gas from expirmnt measured fraction:
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(%)(Pb-47) = partial press
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What is the 47 value?
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Water vapor pressure
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If the fractional concentration of CO2 at end of exhalation is 0.05 (5%), what is the PCO2? Where?
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.05 x (740-47) = 34.7 mm Hg
-This is equiv to both alveolar and arterial PCO2 |
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What is the normal PCo2 value for a healthy young person?
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40 mm Hg
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If the fractional concentration of O2 at end of exhalation is 0.17 (17%), what is the PO2? Where?
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.17 x (740-47) = 117.8 mm Hg
-This is equiv to only alveolar PO2 -> arterial is 6 mm hg lower (111 mm Hg) |
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What is the normal atmospheric PO2?
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150 mm Hg
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What is the normal alveolar PO2?
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100-105
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Why do alveolar O2 and CO2 levels differ from atmospheric?
(3 reasons) |
1. Dead space
2. FRC 3. Continuous alveolar-cap exchange |
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Why does dead space make alveolar O2/CO2 levels different from atmospheric?
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Because we reinhale some gas with every inspiration that we exhaled on the previous breath.
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How does FRC contribute to the alveolar O2/CO2 levels being different from atmospheric?
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We never completely empty the lungs with each breath
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How does humidity affect the gas percentage that we inhale?
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It reduces the O2 level of inhalate
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How would Po2 and PCO2 levels differ in end-expirate samples vs a mixture of all expirate?
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End-expirate would have less O2 and more CO2
(mixed has more O2 and less CO2) |
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What type of air was in the bag of expirate from Josh? What was its composition like?
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Alveolar air + Deadspace Air
-More O2 than alveolar air -Less Co2 than alveolar air |
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How is the difference between mixed expirate vs end-expirate gas levels useful?
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Allows calculation of dead space volume
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What is the equation for dead space volume?
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Tidal Vol x(FACo2 - FECO2)/FACo2
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What is FACO2?
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Fractional concentration of alveolar CO2
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What is FECO2?
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Fractional concentration of mixed expired air CO2 (in bag)
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What is the normal tidal volume?
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500 mL
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What is the normal respiratory rate?
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10 breaths / min
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What is a typical calculation for dead space?
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Vd = 500 x (5%-3%)/5% = 200 mL
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How do you calculate Dead Space Ventilation?
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Vd x RR = 200 x 10 bths/min = 2L per min
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What does calculating dead space ventilation allow us to calculate?
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Alveolar ventilation
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What is the formula for Alveolar ventilation?
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Va = Vtotal - Vd
Va = 5L/min - 2L/min = 3L/min |
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So what percent of inhalation goes to alveoli and dead space?
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Dead space gets 40% of TV
Alveoli get 60% of Tidal vol |
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What is Anatomic dead space?
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The volume of the conductive airways themselves - trachea and bronchi.
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What is Alveolar dead space?
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A component of the underperfused alveoli in a diseased person; gets added to normal anatomic dead space volume.
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What is Physiologic dead space?
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Anatomic + Alveolar dead space
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What type of dead space is calculated via the bohr equation?
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Physiologic - anatomic plus alveolar.
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What happens to PACO2 if breathing decreases or ceases without a decrease in metabolic rate?
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-PACO2 will increase -> called
Alveolar hypoventilation |
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What is alveolar hypoventilation?
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An increased PACO2 without an increased metabolic rate
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What happens to PACo2 if alveolar ventilation is increased without an increase in metabolic rate?
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PACO2 will decrease -> called alveolar hyperventilation
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Define alveolar hyperventilation:
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Increase in PAO2 without an increased metabolic rate
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What is apnea?
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Cessation of breathing
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What is hypopnea?
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Reduced or slower breathing
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What is the Respiratory Quotient?
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R
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Formula for R
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R = VCO2/VO2
CO2 production/O2 utilization |
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Formula for calculating PAco2:
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VCO2/VA(Pb-47)
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Formula for calculating PAo2:
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PIO2 - PaCO2/R
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What is the respiratory quotient (R) when you're burning pure glucose?
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1
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What is the normal resp quotient?
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8:10
(CO2:O2) |
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If you take a dog and put him in a warm environment, he starts to pant; is he hyperventilating?
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no; even tho breathing freq and his expirate volume (Ve) increase, his PACO2 doesn't increase so NOT hyperventilating.
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What is it called when a dog pants?
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Tachypnic hyperpnea
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What is the measurement that best assesses hypo or hyperventilation?
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PACO2
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How is pleural pressure distributed during normal breathing in upright position?
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-More negative at top of chest
-Less negative at bottom of chest |
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Why is the top of the lung more negative when you're upright than the bottom of it?
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Because gravity makes the weight of the lung hang down, expanding upper regions, creating more neg pressure at the top of the lung.
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What happens to the vertical pressure gradient in the lung if a person lies down horzontally?
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It becomes a horizontal pressure gradient
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What is the result of inspired air distrubution due to the vertical Ppl gradient?
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The top of the lung is relatively more full than the bottom of the lung. (more sucking force up high)
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2 factors that cause non-uniform distribution of inspirational air:
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1. Vertical Ppl gradient
2. The fact that the compliance curve is nonlinear |
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When starting from FRC, where will air flow preferentially? Why?
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To the bottom of the lung because it is more compliant
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When starting from RV where will inspired air flow preferentially? Why?
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To the top - because now it's more compliant.
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At FRC, how full is the:
-Upper lung -Lower lung |
Upper is almost 70% full
Lower is almost 30% full |
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When inspiring a tidal breath, where does most of the air go?
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To the bottom of the lung
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Why does more air go to the lower lung during TV breathing?
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Because the upper part of the lung is less compliant, and less air is exchanged during breathing.
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How does the decreasing pleural pressure during inhalation distribute over the lungs?
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Equally in both upper and lower portions; the Ppl gradient is maintained, but negativity is increased.
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didn't finish this lect
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ok
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