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25 Cards in this Set
- Front
- Back
Vt
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- tidal volume
- volume inspired or expired with normal breath |
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FRC
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- Functional Residual Capacity
- sum of ERV and Residual Volume - cannot be measured by spirometry |
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ERV
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- Expiratory Reserve Volume
- volume that can be expired after expiration of tidal volume - amount left after normal exhalation |
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IRV
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- Inspiratory reserve volume
- amount that can be expired over and above tidal volume - used during exercise |
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RV
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- residual volume
- volume that remains after maximal expiration - cannot be measured by spirometry |
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IC
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- inspiratory capacity
- Vt + IRV - normal inspiration and deep breath |
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spirometry
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- measurement of volume of air entering and leaving lungs
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Lung capacities
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1) Inspiratory Capacity (Vt + IRV)
2) Functional Residual Capacity (ERV + RV) 3) Vital Capacity (Forced Vital Capacity) (Vt+ IRV + ERV) |
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FVC
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- Forced vital capacity
- Vt + IRV + ERV - air forcibly expired after maximal inspiration |
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TLC
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- Total lung capacity
- sum of all four lung capacities - volume in lung after maximal inspiration - can't be measured |
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Dead Space
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1) Anatomic Dead space
2) Physiologic Dead Space |
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anatomic dead space
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- volume of conducting airways
- ~150 ml |
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Physiologic dead space
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- volume of lungs not participating in gas exchange
- normal lung = anatomic dead space - in ventilation/perfusion (V/Q) defects can be greater -Vd = physiologic dead space (ml) PaCO2 = PCO2 of arterial blood (mmHg) PECO2 = PCO2 of expired air Vd = Vt (PaCO2 - PECO2)/ PaCO2 - tidal volume times (dilution of alveolar PCO2 by dead space air |
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Minute ventilation
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Vt x breaths/min
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alveolar ventilation
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(Vt - Vd) (breaths/min)
(tidal volume - dead space) x (breaths/minute) |
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ratios
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- Vital capacity is 80% of TLC
- Reserve Volume is 20% |
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FEV1
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- Forced Expiratory Volume in 1st second of forced maximal expiration
- FEV1/FVC = .8 - obstructive lung disease --> Fev1/FVC decreased - restrictive --> normal or increased |
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Helium dilution
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- from resting, He/O2 mix
- [He] monitored until equilibration reached - volume of system and initial %He known - new volume = volume of system + volume remaining in lungs at end of expiration - FRC = V1(C1-C2)/C2 |
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plethysmography
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- boyle's law to find FRC
- airtight box of known V - P measured in box and at airway during inspiration effort at closed airway - V1 = volume in box - V2 = volume after inspiration - change in volume = volume of thorax - P3 and p4 are pressure in airway before and after inspiration P3v3 = p4(V3+ change in V) - V3 = FRC FRC = P4 (change in V/ change in P) |
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Fowler Method
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- single breath N washout
- measures deadspace - 100% O2 in, V and [N] measured on exhalation - no increase in N initially, but incrases to an S curve gradually before a plateau - horizontal line from plateau, vertical tangent to it, through S curve - alveolar gas = plateau - value at which perpendicular intersects Volume axis is anatomic dead space |
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Bohr Method
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- physiological and anatomical dead space
- yield same as Fowlers - when high physiologic deadspace bohr --> large value - Vd/Vt = - (PaCO2 - PECO2)/ PaCO2 PaCO2 = partial pressure of CO2 in arterial blood PECO2 = partial pressure of CO2 in expired air - normal is .2 - .4 |
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Capnography
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- graphic display of exhaled [C02] v time or expired volume during respiratory cycle
- plateu = pressure of Alveolar CO2 (PACO2) approximates PaCO2 in normal |
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hypocapnia
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- lower than normal PaCO2
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Hypercapnia
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- higher than normal PaCO2
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Hyper and Hypo ventilation
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- refer to PaCO2 levels not rate
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