Download - Principles of Mechanical Ventilation: RT 244
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Abby Erickson, RRTReview of RT 110
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Performed by:• Hand
• Machine
Available for:• Short term• Long term• Acute care• Extended home
care
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S-shaped curve, relationship of plasma PO2 and O2 bound to Hb (SO2)
Flat portion: minor changes in PO2 have little effect on SO2 Strong Affinity!
Steep portion: small drop in PO2 causes a large drop in SO2 Weak Affinity!
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Normal: 4-5L/min VA= Vt-VD VA= (Vt-VD)x f ↑ VA = ↓PaCO2, ↑PaO2
• Hyperventilation ↓VA = ↑PaCO2,↓PaO2
• Hypoventilation Alveolar air equation As PaCO2 ↑ by
1mmHg, PaO2 ↓ by 1.25mmHg
..
.
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Degree of compensation Acid-base balance Cause: respiratory, metabolic,
mixed Oxygenation – degree of hypoxemia Must interpret in the context of the
clinical picture!! • Requires ventilation status• History, signs, symptoms
Acute changes versus chronic
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Pawo: zero* Pbs: zero* Ppl: -5cmH2O -
10cmH2O PA: +1cmH2O -
1cmH2O
*unless pressure applied
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Relative ease with which a structure distends• opposite of elastance
Used to describe the elastic forces that oppose lung inflation
V/P = L/cmH2O 50-170ml/cmH2O normal 35/40 -100ml/cmH2O intubated patient Static Compliance Dynamic Compliance
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Frictional forces associated with ventilation• Anatomic structures• Tissue viscous resistance
Ability of air to flow depends on• Gas viscosity• Gas density• Length and diameter of the tube• Flow rate of the gas through the tube
Raw = PTA/flow cmH2O/L/sec• PTA ≈ PIP – Pplat• Assumes constant flow
Normal 0.6-2.4 cmH2O/L/sec Intubated patients 5-7cmH2O/L/sec (and higher!)
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Attempts to mimic normal physiology
Types:• Iron lung – tank
ventilator• Chest cuirass
Maintained without the need for ETT, tracheostomy, able to talk and eat
Cardiovascular concerns, access to patient
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Above normal ventilating rates with below normal ventilating volumes
HFPPV HFJV HFOV
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Requires airway interface
Applies pressure to create gradient between mouth and lung
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ELECTRICALLY POWERED PNEUMATICALLY POWERED Relies on electricity Wall outlet (AC), battery
(DC) Powers internal motors
which provide gas flow to the patient
High pressure gas source Usually 2 -50psi sources,
air and oxygen Built in reducing valves Pneumatic Fluidic
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Pneumatically powered – 50 psi gas sources• Mixture of air and oxygen allow variable
FiO2• Energy to deliver the breath
Electrically powered• Controls the internal function• May be controlled by a microprocessor
(1980’s)
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OPEN LOOP CLOSED LOOP “unintelligent” systems Does not respond to
changes in patient condition
Does not measure variables or change them
“intelligent” systems Compares the set
variable to the measured variable
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Main inspiratory line Adapter Expiratory line Expiratory valve Adjuncts
• Device to warm/humidify air• Thermometer• Nebulizer• Bacteria filters
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Muscle Pressure• Action of the
respiratory muscles
Ventilation Pressure• Produced by the
ventilator
These pressures produce motion (flow) to deliver a volume of gas to the lung; the volume delivered depends on the lung’s characteristics
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PRESSURE CONTROLLED BREATHING
VOLUME CONTROLLED BREATHING
Maintains the pressure waveform in a specific pattern
Pressure waveform is unaffected by changes in lung characteristics
Volume and flow waveforms vary with changes in lung characteristics
Maintains the volume waveform in a specific pattern
Volume and flow waveforms remain unchanged
Pressure waveform varies with changes in lung characteristics
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Change from exhalation to inspiration Inspiration Change from inspiration to exhalation exhalation
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Signal measured by the ventilator Begins, sustains and ends each of the
four phases of the breath• Trigger variable• Limit variable• Cycle variable
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MANDATORY SPONTANEOUS Ventilator determines
start time Ventilator determines
tidal volume Ventilator determines
both Machine triggers and/or
cycles the breath
Patient determines start of breath
Patient determines tidal volume delivery
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Does not require an endotracheal tube
Use of NPPV has the potential:• to avoid complications of intubation• decrease mortality rates• decrease length of stay
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Achieve exhaled tidal volume 5-7ml/kg Patient ventilator synchrony
• Rise time • Inspiratory sensitivity• Expiratory flow cycling• EPAP to offset autoPEEP
Oximetry Alleviating disease/disorder signs and
symptoms
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Requires patient cooperation and tolerance
Selection of appropriate interface Starting with low pressure initially Allow the patient to hold the mask Reassurance Requires secure fit, leaks are
acceptable
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Mask discomfort Air pressures/Gas flows –gastric
insufflation Aspiration pneumonia Pneumothorax Hypotension Hypoxemia, Mucus plugging Respiratory arrest
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Reversal of the cause of respiratory failure
Stabilization of the patient's condition Gradually decreasing the level of
support (both ventilatory and oxygenation)
Gradually increase the amount of time off NPPV
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The rest of the book! Stay on top of the reading, this term
moves fast Come and see me for questions,
concerns and further review, I am here to help
Class time is limited so plan on additional time for independent study