Lecture 20: Mechanical Ventilation (Exam 3) Flashcards
What is normal ventilation
- Movement of gas in & out of the alveoli & is defined as the maintenance of norm arterial blood CO2 concentration (PaCO2) of 35-45 mmHg
- Also should have a norm respiratory effort, rate, & rhythm
Label the diagram
Slide 4
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What is min ventilation (Ve)
- Tidal vol (Vt) x respiratory frequency
- mL per min
Example on slide 6
3,000 mL/min
Why do we care about ventilation
- Ax drugs can alter the px ability to norm ventilate - this could lead to inadequate gas exchange, hypoventilation & eventually respiratory arrest or cardiac arrest
Slide 7
What are the effects of hypercapnia
- Directly causes vasodilation of peripheral arterioles & myocardial depression which can cause slow heart rate, cardiac arrest, & intracranial pressure
- Indirectly increases circulating catecholamines which can lead to cardia arrhythmias, tachycardia, increased myocardial contractility, & BP elevation
- Narcosis @ paCO2 above 95 mmHg
- Induces complete ax @ 245 mmHg
Define IPPV
- Intermittent positive pressure ventilation
- positive pressure maintained only during inspiration
Define IMV
- Intermittent mandatory ventilation
- Operator sets a predetermined # of positive breaths but the px can also breathe spontaneously
Define PEEP
- Positive end-expiratory pressure
- Airway pressure at the end of expiration is maintained above ambient pressure
- Peep is applied when positive pressure is maintained btw/ inspirations that are delivered by a ventilator
What is CPAP
- Continuous positive airway pressure
- Spontaneous breathing w/ positive pressure during both inspiratory & expiratory cycles
Define HF(N)OT
- High flow (nasal) oxygen therapy
- Admin of warm humidified oxygen via nasal prongs using a commercially ava unit to deliver higher flow rates of O2 & an FiO2 up to 100%
Describe how IPPV is performed by closing/occluding the pop-off valve
- close/occlude the pop off valve & squeezing the reservoir bag until 10 to 20 cm H2O is reached
- The pop off valve is reopened so the px can passively expire
- “manual”
- Preferred method is to utilize the safety occlusion valve instead of actually closing the APL valve (pop off)
Describe how IPPV is performed by machine (“mechanical ventilator”)
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What are the reasons a px may require mechanical ventilation
- Simply the px has failure to oxygenate or ventilate
- Respiratory center depression
- Inability to adequately expand thorax
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What are specific indications for IPPV during ax
- Thoracic sx (lungs cannot be inflated when the chis is open)
- Neuromuscular blocking drugs (If you paralyze the ocular m you paralyze the diaphragm)
- Prolonged ax ( > 60 min)
- Chest wall or diaphragmatic trauma ( px w/ flail chest)
- Maintain a more stable ax plane
- Obesity & special px positing (more like to hypoventilation or have V-Q mismatch)
- Control of intracranial pressure
- Convenience
When should IPPV be started in health SA px
When the ETCO2 reaches the mid 50s
What are the neg CV effects of mechanical ventilation
- Neg pressure is not generated inspiration so venous return to the heart is not enhanced
- IPPV may actually physically impede venous return to the right side of the heart (decreased stroke volume, CO, & arterial BP)
- Exacerbated by prolonged inspiratory time, PEEP/CPAP, obstruction to exhalation, & an excessively rapid respiratory rate
How can CV effect w/ IPPV be overcome
Expansion of the extracellular fluid vol & admin of inotropic drugs
What are the other effects of IPPV
Slide 15
Describe a mechanical ventilator
- Compliant pleated compressible bellows connected to an ax breathing circuit
- Needs power (electricity)
- Needs a driving force (oxygen)
What is a double circuit ventilator
- Refers to two gas sources
Slide 17
What are the guideline for IPPV
- Vt is usually increased above norm spont Vt to compensate for pressure mediated increases in volume of the breathing system & airway
- PIP: how much pressure is given w/ each breath
- I to E ratio: How long in inspiration & expiration; want to spend twice as long in expiratory phase than inspiratory
- Px w/ lung trauma, diaphragmatic hernia, or GI distention may need to have an increased respiratory rate to maintain Ve w/o creating excessive inspiratory pressures
Fill out the chart
Slide 18
Answer the example
Slide 19
Answer is C
What are the steps of an IPPV
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What does the amount of gas delivered to the px depend on
- Resistance & compliance of breathing system
- Pxs respiratory sys
What increases resistance? What can decrease compliance?
Slide 22
T/F: Although inspiratory pressure may not vary of time the Vt may changes as the compliance of the respiratory system changes
True
What happens after IPPV is discont.
Slide 23
Describe volume cycled ventilators
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Describe self inflating resuscitation sys (ambu bag)
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What are recruitment maneuvers (RM)
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