Post on 19-Jan-2016
Mechanical Ventilation 1
2Copyright 2008 Society of Critical Care Medicine
Objectives
Discuss indications and techniques for noninvasive positive pressure ventilation (NPPV)Describe types of breaths and modes of mechanical ventilationOutline settings and monitoring for initiation of mechanical ventilation
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Case Study65-year-old with an exacerbation of COPD
Using accessory muscles and wheezing after 2 bronchodilator treatments
HR 110 beats/min, BP 160/110 mm Hg, RR 30 breaths/min, T 99F(37.2C)ABG on 3 L/min O2: pH 7.24, PCO2 60 mm Hg (8 kPa), PO2 65 mm Hg (8.7 kPa)
What type of respiratory support should What type of respiratory support should be initiated? be initiated?
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Candidates for NPPV
Respiratory condition expected to improve in 48-72 hoursAlert, cooperativeHemodynamically stableAble to control airway secretionsAble to coordinate with ventilatorNo contraindications
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Case Study
Avoids complications of intubationPreserves airway reflexesImproved patient comfortLess need for sedationShorter hospital/ICU stayImproved survival
What are advantages of using non-What are advantages of using non-invasive positive pressure ventilation invasive positive pressure ventilation in this patient?in this patient?
6Copyright 2008 Society of Critical Care Medicine
Case StudyABG on 3L/min O2: pH 7.24, PaCO2 60 mm Hg (8 kPa), PaO2 65 mm Hg (8.7 kPa)
HR 110 beats/min, BP 160/110 mm Hg,RR 30 breaths/min
What are the goals for respiratory What are the goals for respiratory support?support?
What settings should be selected for What settings should be selected for NPPV?NPPV?
How should the patient be monitored?How should the patient be monitored?
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Case Study
After 1 hr of NPPV, the patient has not improvedArterial blood gas on 40% O2: pH 7.20, PaCO2 65 mm Hg (8.7 kPa), PaO2 58 mm Hg (7.8 kPa)
HR 115 beats/min, BP 142/98 mm Hg, RR 32 breaths/min
What is the next step? What is the next step?
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Case StudyOrotracheal intubation is performed
What ventilator mode should be What ventilator mode should be selected?selected?
What tidal volume is optimum?What tidal volume is optimum?
What rate of ventilation should be What rate of ventilation should be set?set?
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Respiratory Cycle
Types of breaths: volume-cycled, time-cycled, flow-cycled
Triggering
Cycling
Respiratory Cycle
ExpirationInspiration
Time (sec)
Air
wa
y P
res
su
re (
cm
H2O
)
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Modes of Mechanical Ventilation
Interface of breath types with patientAssist-control (AC)Pressure support (PSV)Synchronized intermittent mandatory (SIMV)
Continuous positive pressure airway pressure (CPAP)—not a mode of ventilation
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Airway Pressure/Flow Tracings
Expiration
Inspiration
Pre
ssu
reP
ress
ure
Time
Time
Spontaneous ventilation
CPAP
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Assist-control ventilation Volume or time-cycled breaths
Pressure support ventilation Flow-cycled breaths
Modes of Mechanical Ventilation
ExpirationInspiration
Volume assist-control
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Synchronized intermittent mandatory ventilation Volume or time-cycled breaths
SIMV + PSV
Modes of Mechanical Ventilation
Volume-cycled breathSpontaneous
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Patient with COPD exacerbation who failed NPPV
Case Study
What ventilator mode should be What ventilator mode should be selected?selected?
What tidal volume is optimum?What tidal volume is optimum?
What rate of ventilation should be set?What rate of ventilation should be set?
What FIOWhat FIO22 should be delivered? should be delivered?
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Initiation of Mechanical Ventilation
Familiar ventilation modeInitial FIO2 = 1.0; decrease to maintain SpO2 >92% to 94%
Initial tidal volume = 8-10 mL/kgRate and minute ventilation appropriate for clinical needsPEEP to support oxygenationCall critical care consultant for help
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Case Study
Chest radiographVital signsSpO2
Patient-ventilator synchronyArterial blood gas
InspiratorypressuresInspiratory:expiratory ratioAuto-PEEPVentilator alarms
What monitoring and assessment is What monitoring and assessment is needed after initiation of mechanical needed after initiation of mechanical ventilation?ventilation?
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Peak inspiratory pressure (Ppeak)Inspiratory plateau pressure (Pplat) Indicator of alveolar distension
Inspiration Expiration
PpeakPplat
Inspiratory Pressures
Ppeak
Pplat
Pplat 30 cm H2O
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Determinants of inspiratory time with volume ventilation
Tidal volumeInspiratory flow rateInspiratory waveform
Inadequate expiratory timeIncomplete exhalationBreath stacking
Inspiratory: Expiratory Ratio
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Diagnosis Measurement Waveform analysis
Auto-PEEP
Auto-PEEP
Gasflow
Auto-PEEP
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Auto-PEEP
Consequences Inspiratory pressures Hypotension Worsened oxygenation Interventions to decrease auto-PEEP Respiratory rate Tidal volume Gas flow rate
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Questions Questions
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Key PointsGoals of NPPV and mechanical ventilation are support of oxygenation and ventilation and reduction in work of breathingNPPV is best used in the alert, cooperative patient whose condition will improve in48-72 hoursConsider the advantages/disadvantages of different modes when selecting ventilatory supportUse guidelines when initiating mechanical ventilation and adjust based on monitoring