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30 Cards in this Set
- Front
- Back
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What is traditionally thought of as the standard for assessing ventilation?
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- PaCO2
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Which ventilatory measurements can be routinely monitored at the bedside in the ICU?
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- lung volumes & flows
- airway pressures - FiO2s |
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What is the normal value for VT? critical value?
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- 5-8 ml/kg IBW
- < 4-5 ml/kg or < 300 ml |
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What is the normal value for frequency? critical value?
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- 12-20 breaths per minute
- > 30-35 breaths per minute |
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What is the critical value for the rapid shallow breathing index (RSBI)?
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- > 105 w/out PS or CPAP
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What is the normal value for Vd/Vt? critical value?
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- 0.25-0.40
- > 0.60 |
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What is the normal volume for VE? critical value?
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- 5-6 L/min
- > 10 L/min |
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What is the normal value for VC? critical value?
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- 65-75 ml/kg
- < 10 ml/kg |
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What is the normal value for MIP? critical value?
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- neg. 80- neg. 100 cm H2O
- 0- neg. 20 cm H2O |
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What is the process of moving gases between the atmosphere and the lung?
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- ventilation
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What creates the "true" or physiological dead space?
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- the conductive airways and alveolar units that are ventilated but not perfused
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What % of the VT is represented by dead space (VD)?
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- 25-40%
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What may rapid shallow breathing in a critically ill patient at rest indicate?
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- impending ventilatory failure
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What kind of VT may be seen w/ metabolic acidosis, sepsis, or severe neurologic injury?
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- a larger than normal VT
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How much of a VT are patients receiving CMV routinely ventilated with?
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- a VT of 10ml/kg, approximately 2x the normal spontaneous VT
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What happens when a normal spontaneous VT is used during CMV w/out PEEP? How can these conditions be reversed?
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there is:
-a reduction in FRC -an increase in intrapulmonary shunt -and a fall in PaO2 -can be reversed in part or totally by increasing the VT or by applying PEEP |
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What may occur w/ a high VT that increases alveolar pressures (plateau pressure) beyond 30 cm H2O?
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- volutrauma may occur
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What is volutrauma?
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- a lung injury that occurs from overdistension of the terminal respiratory units
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What can the application of PEEP in combination w/ a smaller VT do?
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- maintain FRC and prevent the fall in PaO2
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What can a low measured VT be caused by and what is this problem commonly seen with?
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- "stacking" (dynamic hyperinflation)
- seen w/ severe airway obstruction |
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What is the problem caused by dynamic hyperinflation?
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- this problem creates higher peak airway pressure and barotrauma may result
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What can be done to help resolve dynamic hyperinflation?
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- increasing expiratory time w/ bronchodilators and decreasing VT may help resolve the problem
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How can expiratory time be increased?
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- by reducing ventilator rate (if inspiratory time remains the same), increasing inspiratory flow rate, or decreasing inspiratory time
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What is the benefit of proximal volume monitoring (monitoring closest to patient)?
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- eliminates the loss of compressible volume to the circuit and may reflect a more accurately delivered VT than does expiratory limb monitoring
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What types of patients should be ventilated w/ a lower VT of 6-8 ml/kg?
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- those at risk of air trapping and dynamic hyperinflation or ARDS
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What is the criteria used to define failure of the spontaneous breathing trial (SBT)?
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- 20% increase/decrease in blood pressure or HR
- SPO2 less than or equal to 85%-90% - RR > 35 breaths/min - change in mental status - accessory muscle use - onset of diaphoresis - VT of atleast 300 ml or > 4ml/kg |
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What is the formula for the rapid shallow breathing index (RSBI)?
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- RSBI= f/VT
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What RSBI values have been strong prognostic indicators of weaning failure?
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- RSBI values > 105
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What is the average minute ventilation (VE) for a normal healthy adult?
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5-6 L/min
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When is the VE often increased?
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- in the early stages of respiratory failure
- it is not until later stages of failure that VE begins to fall |
