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30 Cards in this Set
- Front
- Back
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What does it mean if a higher-than-normal VE is associated w/ a normal PaCO2 in a patient w/ a normal metabolic rate? What is this usually associated with?
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- there must be an increase in wasted or dead space ventilation
- hypovolemia or pulmonary embolism |
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What else may cause an increase in VE w/ a normal PaCO2?
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- an increase in CO2 production caused by an increased metabolism (as occurs w/ fever or trauma)
- high carbohydrate loading accompanying glucose administration via parenteral feedings |
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What can changes in FRC have a dramatic effect on?
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- gas exchange
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Why is it important to monitor airway pressures?
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- to help determine the need for mechanical ventilation & the patient's readiness for weaning
- to help determine the site and thereby cause of impedance to mechanical ventilation - to evaluate elastic recoil & compliance of the intact thorax - to help estimate the amount of positive airway pressure being transmitted to the heart & major vessels - to help assess the patient's resp. muscle strength |
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What is the maximum pressure attained during the inspiratory phase of mechanical ventilation?
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- peak inspiratory pressure (PIP)
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What does PIP reflect?
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- the amount of force needed to overcome opposition to airflow into the lungs
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What is probably occurring if the PIP increases while the plateau pressure is unchanged? What are the common causes of this?
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- an increase in Raw
- bronchospasm, airway secretions, mucus plugging |
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What is a high PIP considered to be the cause of?
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- barotrauma
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What does static (plateau) pressure more accurately reflect than does peak pressure?
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- alveolar pressure
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What should static pressure be used as the primary indicator for?
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- alveolar rupture
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What is the pressure required to maintain a delivered VT in a patient's lungs during a period of no gas flow?
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- plateau pressure
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What is the average pressure recorded during the positive-pressure and spontaneous phases of a respiratory cycle?
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- mean airway pressure (Paw)
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What is mean airway pressure (Paw) calculated to determine?
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- the average airway pressure being applied to the lungs
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What is the maximum inspiratory pressure (sometimes called NIF or negative inspiratory force)?
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- the maximum inspiratory pressure the patient's ventilatory pump is capable of generating against a closed airway
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What factors influence the patient's ability to produce a normal maximum inspiratory force?
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- respiratory muscle strength
- patient effort - ventilatory drive - lung volume - phrenic nerve function - nutritional status - oxygenation status - acid/base status |
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When is mechanical ventilation usually indicated in patients w/ neuromuscular disease?
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- when serial measurements of VC decrease to < 10 ml/kg or 1 L, and MIP has lessened to -20 cm H2O or less
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What will mechanically ventilated patients develop if they do not complete exhalation before inspiration begins
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- autoPEEP
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What can autoPEEP result from?
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- airways obstruction that increases during exhalation and causes insufficient time for exhalation
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What is defined as volume change per unit of pressure change, or the amount of lung volume achieved per unit of pressure?
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- compliance
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What does dynamic compliance represent?
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- the total impedance to gas flow into the lungs
Cd= corrected VT/PIP-PEEP |
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What is static compliance?
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- the lung volume change per unit of pressure change during a period of no gas flow
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What is static compliance a reflection o
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- the combination of chest wall & lung compliance
Cs= corrected VT/Pplat-PEEP |
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What is the range for normal static compliance values in patients receiving mechanical ventilation?
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40-80 ml/cm H2O
-compliance values of < 20-25 ml/cm H2O are not usually associated w/ successful weaning attempts or PEEP withdrawal |
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How should the critical care practitioner evaluate the integration of the ventilator to the patient?
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- w/ a sequential evaluation starting with the patient (use of accessory muscles, color, diaphoresis, HR, RR) and airway (type, size, integrity, & stability), progressing down both limbs of the ventilator circuit (leaks, temp, & condensate), and terminating w/ the vent. settings & patient monitoring panel
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What does the continuous display of the airway pressure waveform provide the opportunity to visually evaluate?
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- airway pressure levels
- characteristics of the airway pressure curve during all breath cycles - mode of ventilation - estimations on the respiratory work - adequacy of inspiratory flow pattern & peak flow - inspiratory resistive load (peak-plateau pressures) - gross estimates of patient inspiratory effort - estimations of the level of synchrony between the patient & ventilator |
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What is the volume-time waveform most often used to compare?
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- the inspiratory & expiratory delivered volumes
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What does the flow-time waveform allow the clinician to evaluate?
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- both inspiratory & expiratory flow rates
- characteristics of the flow profile during all breath cycles - presence of air trapping (i.e. autoPEEP) -estimations of inspiratory effort - estimations of the level of synchrony between the patient & the ventilator |
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What is occurring if the expiratory flow of a flow-time waveform does not return to zero before inspiration begins?
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- airtrapping and auto-PEEP
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What is one of the prime functions of ventilation?
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- elimination of CO2, one of the byproducts of tissue metabolism
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What can monitoring of exhaled CO2 w/ either capnometry (simple measurement) or capnography (graphing the measurement against time) detect changes in?
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- metabolic rate as a result of cardiac output & body temp. changes, shivering, seizures, trauma, and high carbohydrate infusion
- ventilator function such as a patient disconnection or apnea - efficiency of ventilation (by looking at the increase and decrease in alveolar and dead space ventilation) - transport of CO2 as a result of changes in perfusion |
