Term
| what is the alveolar gas equation? what can it be simplfied to? what is it calculating? |
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Definition
| PAO2 = (.21)(760-47) - PaCO2/R which can be simplified to PAO2 = 150-40/.8 under normal circumstances. it is calculating the level of O2 that is in the alveoli, available to diffusion into the pulmonary vein (function of the arterial blood gas). (a fudge factor for computing PaCO2/R is 1.2xPCO2) |
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Term
| how is the alveolar gas equation used? |
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Definition
| a pt comes in, is hypoxic, do you put them on 50% O2, and get an ABG. therefore you can plug in .5 for the FIO2, 760 for the atm, and PCO2 from the ABG. the alveolar O2 pressure will then be = .5(760-47) - 1.2 (PCO2 from ABG) |
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Term
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Definition
| the PAO2 (from the alveolar gas equation) minus the pa02 (from the ABG), which will tell you if the lungs are adequately loading the blood with O2 |
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Term
| what do you need to check on a hypoxic pt who has a good pulse ox? |
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Definition
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Term
| if a pt is breathing fast, what might their body be trying to do in terms of pH balance? |
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Definition
| blow off CO2, which will make their blood less acidic. less acidic blood allows Hb to retain O2 better |
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Term
| what causes a respiratory acidosis? |
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Definition
| not breathing in the appropriate amount of O2, not breathing out the appropriate amount of CO2 |
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Term
| what causes a metabolic acidosis? what may this result in? |
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Definition
| if a pt is diabetic, glucose levels rise and cause the blood to become more acidic. this may result in respiratory compensation (respiratory alkalosis) |
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Term
| what can cause metabolic alkalosis? |
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
| what are signs of likely respiratory acidosis? |
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Definition
| increased CO2 levels, increased HCO3- levels (CO2 binds w/water = bicarb) |
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Term
| what are signs of likely metabolic acidosis? |
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Definition
| decreased bicarb b/c metabolic acids are producing H+ ions and decreased CO2 b/c body is compensating |
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Term
| what are signs of likely respiratory alkalosis? |
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Definition
| decreased CO2 (definition of hyperventilation) |
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Term
| what are signs of likely metabolic alkalosis? |
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Definition
| increased bicarbonate levels - appropriate bicarb ingestion/retention/iatrogenic |
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Term
| what is winters formula? what is it used for? |
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Definition
| winters formula: PaCO2 = (1.5)(HCO3-)+8+/-2. this gives you the expected CO2, so if the CO2 from the ABG is higher, you would look for resp acidosis/if it is lower, you would look for metabolic acidosis |
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Term
| what are ancillary functions of the lung? |
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Definition
| endocrine (angiotensin I -> II), thermoregulation |
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Term
| how can lung overcompliance lead to pneumothorax? |
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Definition
| they can take air in easily, but do not have the recoil to correctly expel it - the excess air eventually pops an alveolus and air gets between the visceral and parietal pleura |
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Term
| what is pulmonary respiration? |
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Definition
| # of breaths per unit time |
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Term
| what can help pts with sleep apnea? |
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Definition
| continuous positive airway pressure - keeps lungs from deflating too far |
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Term
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Definition
| when an elderly pt who may not be able to regain lung strength after being intubated needs airway pressure nonetheless. this is a mask that can provide continuous positive airway pressure and positive end expiratory pressure as well as monitor and adjust said pressure. |
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Term
| how do higher acid levels affect Hb? |
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Definition
| Hb will drop O2 easier. (more alkolotic: Hb will hold O2 tighter) |
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Term
| what is the haldane effect? |
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Definition
| hypercarbic - O2 comes off easier (more acidic) |
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Term
| how does 2,3-BPG affect Hb? where does it come from? |
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Definition
| 2,3-BPG causes Hb to drop O2. it comes from anerobic glycolysis in the cells, and enhances O2 levels there. |
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Term
| how does a pulse oximeter work? |
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Definition
| unsaturated Hb absorbs red light, while oxygenated Hb reflects it - the pulse oximeter quantifies this. however, you still need to know Hb levels to determine total body oxygen level |
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Term
| what happens in emphysema? |
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Definition
| lungs are overcompliant - do not exhale well and trap air |
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Term
| henderson hasselbach equation: |
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Definition
| blow off CO2, pH goes up/increase CO2, pH goes down |
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Term
| if you have appropriate breathing, what do you need to match it? |
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Definition
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Term
| how do you calculate alveolar ventilation? |
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Definition
| subtract known volume of the upper airway (trachea, carina & bronchi), somewhere between 200-150 mL = dead space, from the tidal volume multiply by the frequency |
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