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42 Cards in this Set
- Front
- Back
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Diffusion of gasses pertains to what principle?
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Ficks law- Diffusion of gasses is: Proportional to:
Partial pressure differences across the membrane Area of the membrane surface Solubility of gas in the membrane Inversely proportional to: Thickness of the membrane Square root of the molecular weight |
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What is the formula for Alveolar ventilation?
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VA=VT – VD
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In the apneic patient what is the primary concern for complication?
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Hypercarbia not oxygenation because even in the paralyzed patient b/c of negative intrathoracic pressures air will still be pulled in.
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How much of alveolar ventilation is dead space?
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1/3 or VT= 3cc/# (VD= 1cc/# + VA= 2cc/#= VT 3cc/#)
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If VT= VD what will happen?
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No gas exchange will occur
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What are the characteristics of high frequency ventilation?
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Increased Cycles- 60+/min
Low Vt-approaches dead space Decreased PAP-but sustained throughout cycle Minimal circulatory impairment due to decreased PAP Less interference w/ SV due to better pt tolerance (less sedation/MR) |
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What are the characteristics of High Frequency positive pressure ventilation?
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Vt-3-5 cc/kg-slightly higher than dead space
Rate of 60-100 CO2 is eliminated with passive expiration |
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The method of ventilation to remove CO2 in IPPV and HFPPV is by?
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Bulk flow- volumes larger than Vt of air in/out
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Characteristics of HFJV?
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Cycles on Hz
Velocity is different in the center of the airway vs. the sides No bulk flow of gasses Rates are usually 60-600 CPM VT is less than VD- (2-5ml/kg) CO2 elimination is continuous thru an open system |
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HFJV has how many cycles?
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1-10Hz as 1 Hz= 60cpm (60-600 cpm as above)
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Which method of advanced ventilation is used in pediatrics?
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High Frequency Oscillations-Rate 600-900 (oscillates 1400-3000)
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What are the key aspects of HFJV that affect its use?
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Driving pressure
I:E ratio-30% Jet catheter size and configuration Rates-60-100 FIO2 Humidity |
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What is the single most important factor affecting HFJV?
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Driving pressures-DP –start @20 (26-35 psi)
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How is DP measured?
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In psi-, which is measuring the pressure of the force of carrier, gasses not IA
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Driving pressure works under what principle?
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Venturi effect-velocity of airflow increases thru a small orifice resulting in a decreased pressure at the outflow of the jet injector, which helps overcome increased resistance of a smaller jet tube, and gas will be entrained increasing the Vt 10-20%
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Why can’t IA agents be used in jet ventilation?
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can’t measure the amount being given
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The most important concepts to remember when administering jet ventilation with entrained gasses is?
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Leave the APL open to allow exhalation and primary narcotic technique + propofol
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What is I: E ratio?
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The percent of inspiratory time to expiratory time during a ventilatory cycle
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Minute ventilation is most dependent upon what factors?
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DP and I:E
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Increasing the I: E ratio will change what factors of the ventilation?
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Increase Vt and minute ventilation (increase Vt because increasing inspiratory time allows more time for inspiration)
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How much of a cycle should be inspiratory with HFJV?
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1/3
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What should the characteristics of the catheter be for HFJV?
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Larger will have greater jet volume and minute ventilation and should have 2-4 side ports
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Hypoventilation when using HFJV should be corrected how?
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Increase the DP and I: E
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Rates outside the recommended allowances will affect ventilation how?
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<60 will increase inspiratory time and improve CO2 elimination
> 400 will decrease inspiratory time and worsen CO2 elimination |
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A major difference b/t jet ventilators and hand jet ventilators is?
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Hand jet ventilators do not have end expiratory alarms to detect escape pressures; therefore it is not possible to detect high build up of pressures at the end of expiration (stacking breaths = Pneumo)
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What are the main alarms on a jet ventilator?
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End expiratory alarm-non defeatable but adjustable-default 20
Peak inspiratory-default 50 |
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What are the initial settings on a jet ventilator?
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DP start at 20 =26-35psi
I: E- 30-50% Rate-100-150 Children DP-10-20 |
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Definitive assessment for settings of HFJV should be based upon what?
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ABG’s
Secondary-chest excursion, SaO2, ETCO2 |
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ETCO2 monitoring should incorporate what awareness?
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That the capnograph is meaningless and turning off the JV and giving a sigh is the best assessment
Otherwise use ABG’s to follow |
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How is CO2 elimination improved in HFJV?
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Increase DP
Increase I:E Increase Entrainment-larger catheter closer to the carina Decrease rates to increase inspiratory time and improve CO2 elimination (remember for HFJV) |
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What is the major determinant of oxygenation of HFJV?
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Airway pressure
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How do we improve PAO2 during HFJV?
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Increase DP
Increase FiO2 Increase I:E ratio |
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How does increasing DP affect oxygenation?
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Will increase mean, peak, and PEEP pressures. Increase Peak Inspiratory pressures are a determinant of flow.
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What are the adverse affects of HFJV?
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Barotrauma – if APL closed, kinked tube or upper airway obstruction
Atelectasis- due to no sigh breaths with HFJV |
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A major disadvantage to use of HFJV is?
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You cannot use IA
Atelectasis can form easily if used for a long time Ineffective ETCO2 and peak pressure monitoring Lack of scavenging |
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Concern with use of rigid bronchoscope with jet ventilation is?
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When scope D/C’d then pt is apneic
No ETCO2 |
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When is the HFJV used in the ICU?
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Bronchopleural fistula
ARDS |
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When is HFJV used in the OR?
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Airway competition
Tracheal/Lung sx Emergency airway Endoscopy |
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Benefits to ICU HFJV?
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Awake pts that can talk makes weaning easier
Can be synchronized with the EKG cycle for optimal performance in severe CHF pts Can possibly decrease ICP due to lower peak pressures |
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What PSI should the hand jet be ventilated to?
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10-15 psi
Should be ventilated at 100 CPM with IE ratio of at least 1:3 |
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Absolute contraindication of manual jet ventilation includes?
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Total airway obstruction-airway trapping
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The key to ventilation with Jet Venting is what?
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Minute ventilation regulated with DP and I:E ratios
Vt does minimal and should be considered a subset of MV as slicing the “pie” into smaller pieces but not really affecting ventilation |
