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289 Cards in this Set
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- 3rd side (hint)
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ĀāĒēĪīŌōŪū
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ĀāĒēĪīŌōŪū
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five
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six
seven |
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size
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shoe
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ĀāĒēĪīŌōŪū
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ĀāĒēĪīŌōŪū
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afs
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ĀāĒēĪīŌōŪū
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ĀāĒēĪīŌōŪū
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ĀāĒēĪīŌōŪū
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one
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hint
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seven
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three
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test
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four
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free
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fly
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home
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base
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new
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syntax
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test
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again
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test
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three
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Question without side 3
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Question without side 3
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Answer without side 3
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What is the driving force for gas diffusion across the alveolar capillary membrane?
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Partial Pressure Gradients
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What is the partial pressure of O2 at sea level?
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#ERROR!
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Gas Measurements in anesthesia
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Life Support Gases: Oxygen-in, CO2 out.
Delivery of Volatile Anesthetics: MAC Values, Inspired and Expired Concentrations Spirometry: PEEP. Vt, Minute Volume, etc. |
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What is the only way to tell if you have a hypoxic gas mixture?
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The oxygen analyzer
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What are the anesthetic gases monitored and how are they monitored?
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O2 - oxygen analyzer and SpO2
CO2 - Capnography Volatile Agents: MAC values, Fi Agent, Fe Agent Drive Gases - (compressed air or O2) - flow rates and flow patterns. |
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Why is monitoring gases a challenge?
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The gases all have diff molecular structures, the machines are all different and work in different ways. Some of them measure at different locations.
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Daltons Law
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The total pressure of a mixture of gases equals the sum of pressures that each would exert if it were alone
Pt = P1 + P2 + P3 |
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How do you calcluate the partial pressure of a gas in room air?
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% gas in mixture * atmosphere pressure (760 mmHg)
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The partial pressure of oxygen can be altered by
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Partial Pressure = % concentration in mixture * atmospheric pressure.
The partial pressure oxygen can be altered by 1) Changing the FiO2 2) Changing the atmospheric pressure |
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What is O2 tension?
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The partial pressure of O2 dissolved in a liquid.
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The greatest fall in O2 tension occurs where?
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The greatest fall in O2 tension occurs across the systemic capillaries.
(b/c O2 gets used by the capillaries). |
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Mixed venous PO2 is normally what value?
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40 mmHg
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What tissues extract a greater portion of O2 from arterial blood?
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The heart and brain because more metabolically active.
These have a lower PVO2 leaving them. |
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What does sepsis do to PVO2?
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Blood spends a longer amt of time in the tissues due to venous pooling. More O2 extraction from Hgb. Blood returning to heart has a really low PvO2
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The partial pressure of O2 in the mitochondria is often ______ _______ than at the end of the systemic capillary.
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The partial pressure of O2 in the mitochondria is often considerably lower than at the end of the systemic capillary.
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What is the formula for calculating O2 content (O2 Carrying Capacity)?
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[1.36 * Hgb value * SpO2] + PaO2 * 0.003
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Oxygen content or oxygen carrying capacity is dependent on...
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Hemoglobin levels.
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Tell me the Inhaled and Expired concentrations of O2, CO2, and H2O Vapor
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O2: Inhaled: 21% Exhaled: 14.6%
CO2 Inhaled: 0.04% Exhaled: 4% H2O Vapor Inhaled: 1.25% Exhaled 5.9% Therefore you exhale more water than you breathe in and you exhale more CO2 than you breathe in (the byproducts of metabolism). |
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How many mL of O2 are attached to onegram of hgb?
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1.36 mL
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What type of molecules cannot be measured with infrared light technology?
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The single atom molecules do not absorb infrared light and cannot be measured using this technology.
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Mass Spectrometry
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MEASURES MOST/ ALL GASES - CO2, O2, AGENTS, ETC.
Collects samples of gas. Passes sample thru a chamber where they become ionized. It then analyzes those ions to provide information about the molecular weight of the compound and its chemical structure. Slow result time but very accurate, expensive. In the anesthetic setting, one Mass Spectrometry set up will measure 4-32 anesthetizing locations. Will work on molecules with only one atom. (Unlike infrared analyzers). |
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How does infrared Spectroscopy work?
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Different gases have SPECIFIC and UNIQUE light absorption spectra.
Infrared spectroscopy shines a light through polyatomic molecules. The molecules have specific light absorption qualities. It compares the amt of reflected or passed through light to a sample with no CO2. Ex: Pulse Oximeter: reflective ones are on the forehead. The pass through ones are on the fingers. |
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Changes in ETCO2 reflects changes in ...
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1) Ventilation
2) Diffusion 3) Perfusion |
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A slowed alveolar plateau phase is indicative of
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Partial Airway Obstructions
Bronchial Intubations |
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Advantages of Time Capnography
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* Simple and convienient
* Monitors intubated and non-intubated patients * Works with spontaneous ventilation * Monitors dynamics of inspiration and expiration |
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Is capnography without a closed breathing system accurate?
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No
Just tells you that the patient is breathing. |
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Can you use a volume capnograph on a non-intubated patient?
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No.
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Can you use a side stream sample for a volume capnograph?
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No.
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A sudden drop in ETCO2 could be caused by
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Circuit leaks and disconnects. Circuit kinks.
Accidental Complete Extubation |
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Causes of Temporarily Spiked CO2 Production
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Sodium Bicarbonate Adminstration
Tourniquet Release Venous CO2 Embolism On capnograph, you will see a temporary spike in ETCO2 |
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Characteristics of Volume Capnograms
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* Requires special equipment and computer
* Requires mainstream cuvette instead of side stream monitoring. * Requires intubation and a ventilator. * Assess Dead Space (Cannot use with spontaneous respirations or on an LMA). |
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Raman Gas Analysis
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When a high intensity laser bounces light off a sample material, most of it comes back the same but some of it will be a diff color.
By analyzing that color, you can determine what kind of molecule the light encountered in the sample, and thereby get a gas value. |
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The normal A-ADCO2 gradient is
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2-5 mmHg with normal physiology
1-2 mmHg in children |
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What is better ventilated, the upper lobes or the lower lobes?
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Upper lobes
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What is better perfused, the upper lobes or the lower lobes?
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Lower lobes
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Overall normal V/Q relationship is
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0.8
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Why is the a-ADCO2 small in shunts?
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The alveolar air equilibrates with arterial PaCO2 due to no air movement out of lungs.
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Advantages of Mainstream Capnographs
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* Instantaneous output and reading
* No aspiration of water or mucus. * No lag time * No mixing of gases in the sample tube. |
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Disadvantages of Mainstream Capnographs
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* No multiple gases (ETCO2 only)
* Bulky (could cause accidental extubation) * Traction of ETT * Expensive * Cannot monitor non-intubated patients * Adaptor can add dead space. |
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Which capnography method is safe for pt's with pulmonary edema, main stream or side stream?
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Main stream because it has no aspiration risk of water or mucus into the unit (which would skew readings ).
In a side stream monitor, the mucus can backflow down the side tube and this would skew readings. |
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What can cause an widened a-ADCO2?
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* INCOMPLETE ALVEOLAR EMPTYING
*POOR SAMPLING * VENTILATION-PERFUSION ABNORMALITIES: seen with PE, hypovolemia, arrest, lateral decubitus |
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Shunts...what happens?
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Ventilation is low or zero.
V/Q ratio is low or zero. a-ADO2 is small in a shunt (why?) Caused by: Atelectasis Mucus Plugs Right Main Stem Bronchial Intubation |
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Advantages of the Side Stream Method
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* Inexpensive
*Light Weight * Disposable * Easy to use in non-intubated patients * Multiple gases can be analyzed. |
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Disadvantages of the Side Stream Method
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* Delayed output and measurement
* Falsely low CO2 if catheter has leak, entrains room air. * Water and mucus may obstruct flow of gas into monitoring * Lag time 1-2 seconds |
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Nellcor Capnometer
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Advantage in neonates and children
Lower flow rates of 30 mL/min Eliminates errors in sampling with small tidal volumes and respiratory rates. Eliminates aspiration of water and secretions. |
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In what two ways can you detect abnormal events on a capnograph?
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1) By a changed ETCO2 value
2) Abnormal Waveforms |
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Capnograph Phase I
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Beginning of exhalation.
Anatomical and apparatus dead Space Air is exhaled first, so no increase in CO2 here. |
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Capnograph Phase II
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Rapid Sharp Uprise
Exhalation is continuing. The dead space air is mixing with alveolar exhaled air. CO2 rises. |
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Capnograph Phase III
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Alveolar Plateau
Alveolar exhaled gas is being exhaled. CO2 level plateaus but slightly increases. Plateau is because CO2 is diffusion limited. |
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What causes teh slight increase in CO2 levels during the alveolar plateau?
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Alveoli are expelling their air at different times, not all at once.
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At what point on the capnograph does CO2 first exit the airway?
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Point B
Right before the rapid upstroke (phase II). |
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Where is ETCO2 measured on the capnograph?
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At the end of phase III, right before the rapid downstroke.
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In what examples would the a-ADCO2 levels be increased?
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Age (more V/Q mismatching)
Emphysema (decreased ventilation) Pulmonary Embolus (decreased perfusion) Low Cardiac Output (decreased perfusion) Hypovolemia (decreased perfusion) Large Tidal Volumes (V/Q mismatch) |
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What could cause a sudden loss in expired CO2?
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Disconnection from the vent.
Kinks Complete extubation Obstructed tubes |
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What would cause an exponential fall (not a gradual fall) in expired CO2?
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Circulatory Arrest
Cardiac Arrest Pulmonary Embolism Extreme blood loss Sudden Hypotension. |
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What is the a-ADCO2 level in pregnancy and obesity?
Why? |
Negative Because ETCO2< PaCO2
The can't get their tidal volumes so they have to increase their RR. When they increase their RR, they blow off their CO2. PACO2/ETCO2 = 30-34 mmHg (less than PaCO2) Reduced bicarbonate values (renal excretion of bicarb to prevent alkalosis). |
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What would cause a Gradual Decrease in expired CO2?
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Decreased CO2 Production--> Hypothermia
Hyperventilation (Increase RR and/or increased tidal volumes). A gradual decline in pulmonary perfusion (hypovolemia). |
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What would cause a Gradual Increase in expired CO2?
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* Increase CO2 Production: Fever, Sepsis
* Decreased ventilation, hypoventilation * Partial airway obstruction. |
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What causes Curare Clefts in the Capnograph waveform?
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Partial recovery from an NMB. The diaphram starts flipping, trying to work.
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What do you do if your pt starts getting curare clefts during abdominal manipulation?
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Wait until the abdominal manipulation is over, could be causing it.
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What would cause a sudden but not complete drop in expired CO2?
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Partial Airway Obstruction
Bronchospasm. Sudden leak in the tubing. ETT partial extubation to hypopharynx |
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What would cause a sustained decrease in expired CO2?
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Anything Chronic that would decrease CO2.
(Chronic Hyperventilation)-->High minute ventilation in the vent. Chronic Bronchitis, COPD (cannot release CO2 well). Chronic untreated Asthma. Chronic Hypovolemia - can't perfuse CO2 to lungs to eliminate Pneumonia (can't get it out). |
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What do you do if your patient gets curare clefts at the beginning of sx with on an NMB?
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Check the TOF, may need to give more NMB.
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What do you do if your pt gets curare clefts at the end of sx?
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Don't give more NMB, pt will be waking up soon anyway.
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What causes cardiogenic Oscillations on a capnograph?
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Beating of the heart oscillates the chest at end expiration and inspiration and causes oscillations on the capnograph at this point.
See it with enlarged hearts at slow RR's. |
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What will make cardiac oscillations go away?
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Increasing the RR.
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Verification of ET tube placement is done with...
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sustained ETCO2 values.
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What can cause a sudden rise in the baseline value on a capnograph?
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Exhausted CO2 Absorberor Incompetent Expiratory valve (baseline will rise)
Contaminated sample line (may need to be cleaned or replaced). |
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What are the three Older techniques for measuring FiO2?
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1) POLARGRAPHIC (CLARK ELECTRODE)
--->Electron compartment is isolated in a reaction chamber. When the reduction takes place, it allows a current to flow, creating a POTENTIAL DIFFERENCE. This potential difference reflects how much O2 is present. 2) PARAMAGNETIC ANALYZER ---> O2 is Paramagnetic ---> A blood sample is exposed to a paramagnetic field and than compared to a room air reference sample. ---> The pressure difference across a transducer is proportional to the oxygen partial pressure difference of the sample and of room air. 3) FUEL CELL (GALVANIC OXYGEN ANALYZER) ---> O2 molecules diffuse across a membrane into an electrolyte solution with a cathode and an anode. An electrical current is generated. The current is proportional to the partial pressure of O2 in the inspired gas. ---> Response time is 20 seconds ---> It is accurate to 3% of water vapor ---> Only has a life span of 3 years. |
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What decreases the a-ADCO2 gradient?
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Shunts: atelectasis, mucus plugs, right mainstem intubation.
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What can cause a sudden TRANSIENT rise in expired CO2?
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Released tourniquet on an orthopedic case.
Sodium bicarbonate injection CO2 insufflation from a pneumoperitoneum entrained into the vasculature. Venous CO2 embolism |
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What causes a sloping of the alveolar plateau on a capnograph?
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Asynchronous emptying of the alveoli, which can be seen with obstructive diseases like asthma, bronchitis, COPD.
The severity of the slope reflects the severity of the disease. Can also reflect plugged ETT's (airway obstruction). |
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What two things affect the amt of PaCO2?
ON TEST!!!!!!!! |
CO2 production
Alveolar ventilation. |
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capacitance
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the ability of a substance to hold an electrical charge.
Does NOT effect injury from macroshock. |
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Purpose of LIM
ON TEST!!!!!! |
to identify faulty equipment which will function normally in an ungrounded system.
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As you age, cardiac output...
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DECREASES.
BOTH RESTING AND MAX CO DECREASE. |
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How does body size affect CO?
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The bigger framed you are, the greater your CO.
(In order to get more pefusion to the tissues.) |
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Cardiac Index (CI) =
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CI = CO/BSA
normalizes the data so you can compare diff people of diff body sizes. |
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Why can't you compare CO's of diff sized people?
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Larger people have larger CO's. Not the same throughout the population.
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Males have a _______ CO than females.
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Larger
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Exercise/ increased activity level _______ CO.
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Increases
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How does posture affect CO?
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Lying Down = Larger CO due to increased Central Blood Volume.
Standing up - Decreased CO due to gravity pulling blood away from the chest. |
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Bowditch Effect
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Increasing Heart Rate can increase the strength of contraction. (up to a point).
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_____ determine max velocity and max contractile force of cardiac muscle
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Calcium.
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The ultimate effect of changes in heart rate on cardiac output depends on ___________.
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The ultimate effect of changes in heart rate on cardiac output depends on changes in STROKE VOLUME.
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Explain why the Bowditch Effect is true.
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Bowditch Effect: Increasing Heart Rate can increase the strength of contraction. (up to a point).
WHY?? Increased frequency of depolarizations will increase the amt of intracellular calcium due to slow L-type Ca channels. The Ca will increase the force of contraction. This won't last forever, overtime the tension will fall back to it's normal level. Ultimately the affect of HR on CO will depend on STROKE VOLUME changes. |
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High heart rates (dysrhythmias) can reduce _______ and _______.
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High heart rates (dysrhythmias) can reduce stroke volume and cardiac output.
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At constant _____ CO increases as HR increases.
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stroke volume
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If HR is dramatically increased without exercise (dysrhytmias or drugs), what happens to CO?
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CO will decrease as HR increases.
Ventricular filling time is decreased. Venous return is decreased. |
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Shifts of what curve solely reflect changes in Cardiac Output?
ie What curve is a marker for the inotropic state of the heart? |
Stroke Work plotted against Preload.
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There is a _____ relationship between contractility and cardiac output.
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Direct
Increase contractility, increase cardiac output. Decrease contractility, decrease cardiac output. |
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What curve reflects changes in afterload?
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Cardiac Output plotted against Preload.
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There is a _______ relationship between afterload and contractility.
There is a ______ relationship between afterload and cardiac output. |
There is an inverse relationship between afterload and contractility.
There is an inverse relationship between afterload and cardiac output. |
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There is a _____ relationship between preload and cardiac output in healthy individuals.
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There is a direct relationship between preload and cardiac output in healthy individuals.
THIS IS THE FRANK STARLING LAW. |
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If you physiologically drive up heart rate, (via exercise) what happens to cardiac output?
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CO increases as HR increases.
SNS Effects: 1) Increase the slope of Phase 0 (depolarization) and Phase 3 (repolarization) making depolarization faster and repolarization faster. while somehow still preserving diastolic filling time. 2) Increased Inotropy and lusitrophy: 3) Increased venous return: SNS venoconstricts, decreasing compliance of veins to help with filling. Contracting skeletal muscles also increase venous return. |
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At high heart rates, CO ________ as HR increases.
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At high heart rates (dysrhytmias), CO decreases as HR increases.
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Changes in afterload have no real impact on __________.
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Stroke Work.
Only contractility affects stroke work. |
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The volume of blood returning to the heart per unit time =
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VENOUS RETURN.
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Venous return has a _______ relationship with cardiac output.
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Venous return has a direct relationship with cardiac output.
Affects preload. FRANK STARLING LAW |
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The primary source of central blood volume is
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Venous return.
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A normal heart sits on the _______ limb of the Frank Starling Curve. What determines this point on the curve? What factor LIMITS the ability to travel furthur up the curve?
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Venous Return to the heart.
Preload is limited to the amt of venous return to the heart. In normal people, this does not exceed the preload point on the frank starling curve. |
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Venous return depends on _________.
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Vascular function.
(Venodilation, venoconstriction, etc). |
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Flow IN heart =
Flow OUT of heart = |
Flow IN heart = Venous return
Flow OUT of heart = Cardiac Output |
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In order to get a SUSTAINED CHANGE in cardiac output, one of two things must be altered...
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1) The amount of venous return to the heart.
2) Heart Properties (HR, Contractility, or Afterload). |
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_________ ______ has a direct impact on the amount of venous return.
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Blood Volume has a direct impact on the amount of venous return.
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When considered over time, or in "steady-state conditions", cardiac output and venous return .....
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ARE EQUAL.
But they are not equal from beat to beat. |
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The primary site of whole body resistance is
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the arterioles = afterload = TPR = SVR
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The primary site of whole body compliance
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the veins
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What four Factors affect Venous Return?
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1) Blood Volume (Direct relationship).
-----> BV increased via Renin-Angiotensin Aldosterone system -----> BV decreased by bleeding, sweating, peeing 2) Vein Compliance (Inverse relationship). 3) Muscle Pump (Direct Relationship) 4) TPR (Inverse relationship). - The primary site of resistance is the arterioles...upstream from the veins. |
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T/F
CO and Venous Return are equal from beat to beat. |
FALSE
only over time or in a steady state. |
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There is a _______ relationship between venous compliance and venous return.
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There is an indirect relationship between venous compliance and venous return.
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Four alterable factors that determine Cardiac Output
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1) Heart Rate (directly related but complex)
2) Myocardial Contractility (directly related) 3) Afterload (Inversely Related) 4) Preload (Directly Related) |
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Name the Ways the Body can attempt to increase CO for mild CHF?
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1) Decreased Venous Compliance (not powerful enough to overcome the drop in contractility)
2) Increased Blood Volume (body activates the Renin, Angiotensin, Aldosterone System, causing renal reabsorption of Na and H2O) 3) Muscle Pump (not practical) 4) Decreased resistance to increase venous return - Doesn't happen, would decrease BP |
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Heart Failure is a deterioration of
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Ventricular contractility
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The only real way the body can compensate for decreased contractility and CO associated with Heart Failure is to...
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INCREASE BLOOD VOLUME
via the Renin, Angiotension, Aldosterone system causing water and Na absorption in the kidneys. Problem....this fluid then gets filtered out into Tissues (edema) and body just keeps adding more to maintain CO. Get Edema and Wet Lungs. |
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What is the derogative effect of increased blood volume to compensate for CHF?
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Increased pressures in heart.
Increased hydrostatic pressure in capillaries. Increased capillary filtration --> EDEMA |
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The rate of O2 transfer from the alveolus into the blood is called
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O2 Uptake/ Consumption.
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A-V O2 Difference
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CaO2 - CvO2
The difference b/n arterial and venous concentrations of O2. |
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True or False
The fick equation: VO2 = Q * (CaO2 - CvO2) Can be used for ANY vascular bed. |
TRUE
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When using the Fick Equation (VO2 = Q * (CaO2 - CvO2)) to determine CO, the venous sample must be drawn from....
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A mixed venous sample from the right atrium or the pulmonary artery.
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Classic Signs of Heart Failure
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*Increased HR - Baroreceptor reflex: Decreased stimulation of NTS, Decreased activity of NA and DMV in medulla due to decreased blood pressure.
*Exercise Intolerance - heart can't increase CO to feed the tissue *Orthopnea - postional dypsnea when supine. Bilateral crackles. |
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O2 Uptake/ Consumption (VO2)=
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O2 Uptake/ Consumption = Flow * AV O2 Difference
VO2 = CO * (CaO2 - CvO2) FICK EQUATION Solve for CO (Q) to estimate cardiac output. (MUST MULTIPLY THE FINAL RESULT FOR Q X 100 TO GET L/min!!!!!!!!!!!!!!!!!!!!!) |
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How can you estimate cardiac output with blood samples?
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By using the fick equation.
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Pulmonary Blood Flow = ________ ______.
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Pulmonary Blood Flow = Cardiac Output
Cardiac Output is the same throughout the body. |
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Dye Dilution is a technique used to calculate
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Blood Volume
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What is the driving force for gas diffusion across the alveolar capillary membrane?
|
Partial Pressure Gradients
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What is the partial pressure of O2 at sea level?
|
#ERROR!
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Gas Measurements in anesthesia
|
Life Support Gases: Oxygen-in, CO2 out.
Delivery of Volatile Anesthetics: MAC Values, Inspired and Expired Concentrations Spirometry: PEEP. Vt, Minute Volume, etc. |
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What is the only way to tell if you have a hypoxic gas mixture?
|
The oxygen analyzer
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What are the anesthetic gases monitored and how are they monitored?
|
O2 - oxygen analyzer and SpO2
CO2 - Capnography Volatile Agents: MAC values, Fi Agent, Fe Agent Drive Gases - (compressed air or O2) - flow rates and flow patterns. |
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Why is monitoring gases a challenge?
|
The gases all have diff molecular structures, the machines are all different and work in different ways. Some of them measure at different locations.
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Daltons Law
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The total pressure of a mixture of gases equals the sum of pressures that each would exert if it were alone
Pt = P1 + P2 + P3 |
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How do you calcluate the partial pressure of a gas in room air?
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% gas in mixture * atmosphere pressure (760 mmHg)
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The partial pressure of oxygen can be altered by
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Partial Pressure = % concentration in mixture * atmospheric pressure.
The partial pressure oxygen can be altered by 1) Changing the FiO2 2) Changing the atmospheric pressure |
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What is O2 tension?
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The partial pressure of O2 dissolved in a liquid.
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The greatest fall in O2 tension occurs where?
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The greatest fall in O2 tension occurs across the systemic capillaries.
(b/c O2 gets used by the capillaries). |
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Mixed venous PO2 is normally what value?
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40 mmHg
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What tissues extract a greater portion of O2 from arterial blood?
|
The heart and brain because more metabolically active.
These have a lower PVO2 leaving them. |
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What does sepsis do to PVO2?
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Blood spends a longer amt of time in the tissues due to venous pooling. More O2 extraction from Hgb. Blood returning to heart has a really low PvO2
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The partial pressure of O2 in the mitochondria is often ______ _______ than at the end of the systemic capillary.
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The partial pressure of O2 in the mitochondria is often considerably lower than at the end of the systemic capillary.
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What is the formula for calculating O2 content (O2 Carrying Capacity)?
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[1.36 * Hgb value * SpO2] + PaO2 * 0.003
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Oxygen content or oxygen carrying capacity is dependent on...
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Hemoglobin levels.
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Tell me the Inhaled and Expired concentrations of O2, CO2, and H2O Vapor
|
O2: Inhaled: 21% Exhaled: 14.6%
CO2 Inhaled: 0.04% Exhaled: 4% H2O Vapor Inhaled: 1.25% Exhaled 5.9% Therefore you exhale more water than you breathe in and you exhale more CO2 than you breathe in (the byproducts of metabolism). |
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How many mL of O2 are attached to onegram of hgb?
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1.36 mL
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What type of molecules cannot be measured with infrared light technology?
|
The single atom molecules do not absorb infrared light and cannot be measured using this technology.
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Mass Spectrometry
|
MEASURES MOST/ ALL GASES - CO2, O2, AGENTS, ETC.
Collects samples of gas. Passes sample thru a chamber where they become ionized. It then analyzes those ions to provide information about the molecular weight of the compound and its chemical structure. Slow result time but very accurate, expensive. In the anesthetic setting, one Mass Spectrometry set up will measure 4-32 anesthetizing locations. Will work on molecules with only one atom. (Unlike infrared analyzers). |
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How does infrared Spectroscopy work?
|
Different gases have SPECIFIC and UNIQUE light absorption spectra.
Infrared spectroscopy shines a light through polyatomic molecules. The molecules have specific light absorption qualities. It compares the amt of reflected or passed through light to a sample with no CO2. Ex: Pulse Oximeter: reflective ones are on the forehead. The pass through ones are on the fingers. |
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Changes in ETCO2 reflects changes in ...
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1) Ventilation
2) Diffusion 3) Perfusion |
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A slowed alveolar plateau phase is indicative of
|
Partial Airway Obstructions
Bronchial Intubations |
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Advantages of Time Capnography
|
* Simple and convienient
* Monitors intubated and non-intubated patients * Works with spontaneous ventilation * Monitors dynamics of inspiration and expiration |
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Is capnography without a closed breathing system accurate?
|
No
Just tells you that the patient is breathing. |
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Can you use a volume capnograph on a non-intubated patient?
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No.
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Can you use a side stream sample for a volume capnograph?
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No.
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A sudden drop in ETCO2 could be caused by
|
Circuit leaks and disconnects. Circuit kinks.
Accidental Complete Extubation |
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Causes of Temporarily Spiked CO2 Production
|
Sodium Bicarbonate Adminstration
Tourniquet Release Venous CO2 Embolism On capnograph, you will see a temporary spike in ETCO2 |
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Characteristics of Volume Capnograms
|
* Requires special equipment and computer
* Requires mainstream cuvette instead of side stream monitoring. * Requires intubation and a ventilator. * Assess Dead Space (Cannot use with spontaneous respirations or on an LMA). |
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Raman Gas Analysis
|
When a high intensity laser bounces light off a sample material, most of it comes back the same but some of it will be a diff color.
By analyzing that color, you can determine what kind of molecule the light encountered in the sample, and thereby get a gas value. |
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The normal A-ADCO2 gradient is
|
2-5 mmHg with normal physiology
1-2 mmHg in children |
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What is better ventilated, the upper lobes or the lower lobes?
|
Upper lobes
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What is better perfused, the upper lobes or the lower lobes?
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Lower lobes
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Overall normal V/Q relationship is
|
0.8
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Why is the a-ADCO2 small in shunts?
|
The alveolar air equilibrates with arterial PaCO2 due to no air movement out of lungs.
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Advantages of Mainstream Capnographs
|
* Instantaneous output and reading
* No aspiration of water or mucus. * No lag time * No mixing of gases in the sample tube. |
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Disadvantages of Mainstream Capnographs
|
* No multiple gases (ETCO2 only)
* Bulky (could cause accidental extubation) * Traction of ETT * Expensive * Cannot monitor non-intubated patients * Adaptor can add dead space. |
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Which capnography method is safe for pt's with pulmonary edema, main stream or side stream?
|
Main stream because it has no aspiration risk of water or mucus into the unit (which would skew readings ).
In a side stream monitor, the mucus can backflow down the side tube and this would skew readings. |
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What can cause an widened a-ADCO2?
|
* INCOMPLETE ALVEOLAR EMPTYING
*POOR SAMPLING * VENTILATION-PERFUSION ABNORMALITIES: seen with PE, hypovolemia, arrest, lateral decubitus |
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Shunts...what happens?
|
Ventilation is low or zero.
V/Q ratio is low or zero. a-ADO2 is small in a shunt (why?) Caused by: Atelectasis Mucus Plugs Right Main Stem Bronchial Intubation |
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Advantages of the Side Stream Method
|
* Inexpensive
*Light Weight * Disposable * Easy to use in non-intubated patients * Multiple gases can be analyzed. |
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Disadvantages of the Side Stream Method
|
* Delayed output and measurement
* Falsely low CO2 if catheter has leak, entrains room air. * Water and mucus may obstruct flow of gas into monitoring * Lag time 1-2 seconds |
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Nellcor Capnometer
|
Advantage in neonates and children
Lower flow rates of 30 mL/min Eliminates errors in sampling with small tidal volumes and respiratory rates. Eliminates aspiration of water and secretions. |
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|
In what two ways can you detect abnormal events on a capnograph?
|
1) By a changed ETCO2 value
2) Abnormal Waveforms |
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Capnograph Phase I
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Beginning of exhalation.
Anatomical and apparatus dead Space Air is exhaled first, so no increase in CO2 here. |
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Capnograph Phase II
|
Rapid Sharp Uprise
Exhalation is continuing. The dead space air is mixing with alveolar exhaled air. CO2 rises. |
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Capnograph Phase III
|
Alveolar Plateau
Alveolar exhaled gas is being exhaled. CO2 level plateaus but slightly increases. Plateau is because CO2 is diffusion limited. |
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What causes teh slight increase in CO2 levels during the alveolar plateau?
|
Alveoli are expelling their air at different times, not all at once.
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|
At what point on the capnograph does CO2 first exit the airway?
|
Point B
Right before the rapid upstroke (phase II). |
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|
Where is ETCO2 measured on the capnograph?
|
At the end of phase III, right before the rapid downstroke.
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|
|
In what examples would the a-ADCO2 levels be increased?
|
Age (more V/Q mismatching)
Emphysema (decreased ventilation) Pulmonary Embolus (decreased perfusion) Low Cardiac Output (decreased perfusion) Hypovolemia (decreased perfusion) Large Tidal Volumes (V/Q mismatch) |
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|
What could cause a sudden loss in expired CO2?
|
Disconnection from the vent.
Kinks Complete extubation Obstructed tubes |
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|
What would cause an exponential fall (not a gradual fall) in expired CO2?
|
Circulatory Arrest
Cardiac Arrest Pulmonary Embolism Extreme blood loss Sudden Hypotension. |
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|
What is the a-ADCO2 level in pregnancy and obesity?
Why? |
Negative Because ETCO2< PaCO2
The can't get their tidal volumes so they have to increase their RR. When they increase their RR, they blow off their CO2. PACO2/ETCO2 = 30-34 mmHg (less than PaCO2) Reduced bicarbonate values (renal excretion of bicarb to prevent alkalosis). |
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|
What would cause a Gradual Decrease in expired CO2?
|
Decreased CO2 Production--> Hypothermia
Hyperventilation (Increase RR and/or increased tidal volumes). A gradual decline in pulmonary perfusion (hypovolemia). |
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|
What would cause a Gradual Increase in expired CO2?
|
* Increase CO2 Production: Fever, Sepsis
* Decreased ventilation, hypoventilation * Partial airway obstruction. |
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|
What causes Curare Clefts in the Capnograph waveform?
|
Partial recovery from an NMB. The diaphram starts flipping, trying to work.
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|
What do you do if your pt starts getting curare clefts during abdominal manipulation?
|
Wait until the abdominal manipulation is over, could be causing it.
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|
What would cause a sudden but not complete drop in expired CO2?
|
Partial Airway Obstruction
Bronchospasm. Sudden leak in the tubing. ETT partial extubation to hypopharynx |
|
|
|
What would cause a sustained decrease in expired CO2?
|
Anything Chronic that would decrease CO2.
(Chronic Hyperventilation)-->High minute ventilation in the vent. Chronic Bronchitis, COPD (cannot release CO2 well). Chronic untreated Asthma. Chronic Hypovolemia - can't perfuse CO2 to lungs to eliminate Pneumonia (can't get it out). |
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What do you do if your patient gets curare clefts at the beginning of sx with on an NMB?
|
Check the TOF, may need to give more NMB.
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|
What do you do if your pt gets curare clefts at the end of sx?
|
Don't give more NMB, pt will be waking up soon anyway.
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|
|
What causes cardiogenic Oscillations on a capnograph?
|
Beating of the heart oscillates the chest at end expiration and inspiration and causes oscillations on the capnograph at this point.
See it with enlarged hearts at slow RR's. |
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|
|
What will make cardiac oscillations go away?
|
Increasing the RR.
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|
|
Verification of ET tube placement is done with...
|
sustained ETCO2 values.
|
|
|
|
What can cause a sudden rise in the baseline value on a capnograph?
|
Exhausted CO2 Absorberor Incompetent Expiratory valve (baseline will rise)
Contaminated sample line (may need to be cleaned or replaced). |
|
|
|
What are the three Older techniques for measuring FiO2?
|
1) POLARGRAPHIC (CLARK ELECTRODE)
--->Electron compartment is isolated in a reaction chamber. When the reduction takes place, it allows a current to flow, creating a POTENTIAL DIFFERENCE. This potential difference reflects how much O2 is present. 2) PARAMAGNETIC ANALYZER ---> O2 is Paramagnetic ---> A blood sample is exposed to a paramagnetic field and than compared to a room air reference sample. ---> The pressure difference across a transducer is proportional to the oxygen partial pressure difference of the sample and of room air. 3) FUEL CELL (GALVANIC OXYGEN ANALYZER) ---> O2 molecules diffuse across a membrane into an electrolyte solution with a cathode and an anode. An electrical current is generated. The current is proportional to the partial pressure of O2 in the inspired gas. ---> Response time is 20 seconds ---> It is accurate to 3% of water vapor ---> Only has a life span of 3 years. |
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|
|
What decreases the a-ADCO2 gradient?
|
Shunts: atelectasis, mucus plugs, right mainstem intubation.
|
|
|
|
What can cause a sudden TRANSIENT rise in expired CO2?
|
Released tourniquet on an orthopedic case.
Sodium bicarbonate injection CO2 insufflation from a pneumoperitoneum entrained into the vasculature. Venous CO2 embolism |
|
|
|
What causes a sloping of the alveolar plateau on a capnograph?
|
Asynchronous emptying of the alveoli, which can be seen with obstructive diseases like asthma, bronchitis, COPD.
The severity of the slope reflects the severity of the disease. Can also reflect plugged ETT's (airway obstruction). |
|
|
|
What two things affect the amt of PaCO2?
ON TEST!!!!!!!! |
CO2 production
Alveolar ventilation. |
|
|
|
capacitance
|
the ability of a substance to hold an electrical charge.
Does NOT effect injury from macroshock. |
|
|
|
Purpose of LIM
ON TEST!!!!!! |
to identify faulty equipment which will function normally in an ungrounded system.
|
|
|
|
As you age, cardiac output...
|
DECREASES.
BOTH RESTING AND MAX CO DECREASE. |
|
|
|
How does body size affect CO?
|
The bigger framed you are, the greater your CO.
(In order to get more pefusion to the tissues.) |
|
|
|
Cardiac Index (CI) =
|
CI = CO/BSA
normalizes the data so you can compare diff people of diff body sizes. |
|
|
|
Why can't you compare CO's of diff sized people?
|
Larger people have larger CO's. Not the same throughout the population.
|
|
|
|
Males have a _______ CO than females.
|
Larger
|
|
|
|
Exercise/ increased activity level _______ CO.
|
Increases
|
|
|
|
How does posture affect CO?
|
Lying Down = Larger CO due to increased Central Blood Volume.
Standing up - Decreased CO due to gravity pulling blood away from the chest. |
|
|
|
Bowditch Effect
|
Increasing Heart Rate can increase the strength of contraction. (up to a point).
|
|
|
|
_____ determine max velocity and max contractile force of cardiac muscle
|
Calcium.
|
|
|
|
The ultimate effect of changes in heart rate on cardiac output depends on ___________.
|
The ultimate effect of changes in heart rate on cardiac output depends on changes in STROKE VOLUME.
|
|
|
|
Explain why the Bowditch Effect is true.
|
Bowditch Effect: Increasing Heart Rate can increase the strength of contraction. (up to a point).
WHY?? Increased frequency of depolarizations will increase the amt of intracellular calcium due to slow L-type Ca channels. The Ca will increase the force of contraction. This won't last forever, overtime the tension will fall back to it's normal level. Ultimately the affect of HR on CO will depend on STROKE VOLUME changes. |
|
|
|
High heart rates (dysrhythmias) can reduce _______ and _______.
|
High heart rates (dysrhythmias) can reduce stroke volume and cardiac output.
|
|
|
|
At constant _____ CO increases as HR increases.
|
stroke volume
|
|
|
|
If HR is dramatically increased without exercise (dysrhytmias or drugs), what happens to CO?
|
CO will decrease as HR increases.
Ventricular filling time is decreased. Venous return is decreased. |
|
|
|
Shifts of what curve solely reflect changes in Cardiac Output?
ie What curve is a marker for the inotropic state of the heart? |
Stroke Work plotted against Preload.
|
|
|
|
There is a _____ relationship between contractility and cardiac output.
|
Direct
Increase contractility, increase cardiac output. Decrease contractility, decrease cardiac output. |
|
|
|
What curve reflects changes in afterload?
|
Cardiac Output plotted against Preload.
|
|
|
|
There is a _______ relationship between afterload and contractility.
There is a ______ relationship between afterload and cardiac output. |
There is an inverse relationship between afterload and contractility.
There is an inverse relationship between afterload and cardiac output. |
|
|
|
There is a _____ relationship between preload and cardiac output in healthy individuals.
|
There is a direct relationship between preload and cardiac output in healthy individuals.
THIS IS THE FRANK STARLING LAW. |
|
|
|
If you physiologically drive up heart rate, (via exercise) what happens to cardiac output?
|
CO increases as HR increases.
SNS Effects: 1) Increase the slope of Phase 0 (depolarization) and Phase 3 (repolarization) making depolarization faster and repolarization faster. while somehow still preserving diastolic filling time. 2) Increased Inotropy and lusitrophy: 3) Increased venous return: SNS venoconstricts, decreasing compliance of veins to help with filling. Contracting skeletal muscles also increase venous return. |
|
|
|
At high heart rates, CO ________ as HR increases.
|
At high heart rates (dysrhytmias), CO decreases as HR increases.
|
|
|
|
Changes in afterload have no real impact on __________.
|
Stroke Work.
Only contractility affects stroke work. |
|
|
|
The volume of blood returning to the heart per unit time =
|
VENOUS RETURN.
|
|
|
|
Venous return has a _______ relationship with cardiac output.
|
Venous return has a direct relationship with cardiac output.
Affects preload. FRANK STARLING LAW |
|
|
|
The primary source of central blood volume is
|
Venous return.
|
|
|
|
A normal heart sits on the _______ limb of the Frank Starling Curve. What determines this point on the curve? What factor LIMITS the ability to travel furthur up the curve?
|
Venous Return to the heart.
Preload is limited to the amt of venous return to the heart. In normal people, this does not exceed the preload point on the frank starling curve. |
|
|
|
Venous return depends on _________.
|
Vascular function.
(Venodilation, venoconstriction, etc). |
|
|
|
Flow IN heart =
Flow OUT of heart = |
Flow IN heart = Venous return
Flow OUT of heart = Cardiac Output |
|
|
|
In order to get a SUSTAINED CHANGE in cardiac output, one of two things must be altered...
|
1) The amount of venous return to the heart.
2) Heart Properties (HR, Contractility, or Afterload). |
|
|
|
_________ ______ has a direct impact on the amount of venous return.
|
Blood Volume has a direct impact on the amount of venous return.
|
|
|
|
When considered over time, or in "steady-state conditions", cardiac output and venous return .....
|
ARE EQUAL.
But they are not equal from beat to beat. |
|
|
|
The primary site of whole body resistance is
|
the arterioles = afterload = TPR = SVR
|
|
|
|
The primary site of whole body compliance
|
the veins
|
|
|
|
What four Factors affect Venous Return?
|
1) Blood Volume (Direct relationship).
-----> BV increased via Renin-Angiotensin Aldosterone system -----> BV decreased by bleeding, sweating, peeing 2) Vein Compliance (Inverse relationship). 3) Muscle Pump (Direct Relationship) 4) TPR (Inverse relationship). - The primary site of resistance is the arterioles...upstream from the veins. |
|
|
|
T/F
CO and Venous Return are equal from beat to beat. |
FALSE
only over time or in a steady state. |
|
|
|
There is a _______ relationship between venous compliance and venous return.
|
There is an indirect relationship between venous compliance and venous return.
|
|
|
|
Four alterable factors that determine Cardiac Output
|
1) Heart Rate (directly related but complex)
2) Myocardial Contractility (directly related) 3) Afterload (Inversely Related) 4) Preload (Directly Related) |
|
|
|
Name the Ways the Body can attempt to increase CO for mild CHF?
|
1) Decreased Venous Compliance (not powerful enough to overcome the drop in contractility)
2) Increased Blood Volume (body activates the Renin, Angiotensin, Aldosterone System, causing renal reabsorption of Na and H2O) 3) Muscle Pump (not practical) 4) Decreased resistance to increase venous return - Doesn't happen, would decrease BP |
|
|
|
Heart Failure is a deterioration of
|
Ventricular contractility
|
|
|
|
The only real way the body can compensate for decreased contractility and CO associated with Heart Failure is to...
|
INCREASE BLOOD VOLUME
via the Renin, Angiotension, Aldosterone system causing water and Na absorption in the kidneys. Problem....this fluid then gets filtered out into Tissues (edema) and body just keeps adding more to maintain CO. Get Edema and Wet Lungs. |
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|
|
What is the derogative effect of increased blood volume to compensate for CHF?
|
Increased pressures in heart.
Increased hydrostatic pressure in capillaries. Increased capillary filtration --> EDEMA |
|
|
|
The rate of O2 transfer from the alveolus into the blood is called
|
O2 Uptake/ Consumption.
|
|
|
|
A-V O2 Difference
|
CaO2 - CvO2
The difference b/n arterial and venous concentrations of O2. |
|
|
|
True or False
The fick equation: VO2 = Q * (CaO2 - CvO2) Can be used for ANY vascular bed. |
TRUE
|
|
|
|
When using the Fick Equation (VO2 = Q * (CaO2 - CvO2)) to determine CO, the venous sample must be drawn from....
|
A mixed venous sample from the right atrium or the pulmonary artery.
|
|
|
|
Classic Signs of Heart Failure
|
*Increased HR - Baroreceptor reflex: Decreased stimulation of NTS, Decreased activity of NA and DMV in medulla due to decreased blood pressure.
*Exercise Intolerance - heart can't increase CO to feed the tissue *Orthopnea - postional dypsnea when supine. Bilateral crackles. |
|
|
|
O2 Uptake/ Consumption (VO2)=
|
O2 Uptake/ Consumption = Flow * AV O2 Difference
VO2 = CO * (CaO2 - CvO2) FICK EQUATION Solve for CO (Q) to estimate cardiac output. (MUST MULTIPLY THE FINAL RESULT FOR Q X 100 TO GET L/min!!!!!!!!!!!!!!!!!!!!!) |
|
|
|
How can you estimate cardiac output with blood samples?
|
By using the fick equation.
|
|
|
|
Pulmonary Blood Flow = ________ ______.
|
Pulmonary Blood Flow = Cardiac Output
Cardiac Output is the same throughout the body. |
|
|
|
Dye Dilution is a technique used to calculate
|
Blood Volume
|
|
