1 Pre-ICU Training CHEST Mechanical Ventilatory Support 2008/6/20.

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Pre-ICU TrainingCHEST

Mechanical Ventilatory Support

2008/6/20

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What is Mechanical Ventilator?

• Specially designed pumps that can support the ventilatory function system and improve oxygenation through application of high oxygen content gas and positive pressure.

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Indications for Mechanical Ventilator

• Hypoxemic respiratory failure: PaO2 < 60mmHg with the FiO2 > 60%

• Hypercapnic respiratory failure: pH < 7.35 with PaCO2 > 50mmHg

• Respiratory rate > 35/min

• Others

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Types of Mechanical Ventilator

• Positive pressure vs. Negative pressure

• Invasive vs. Non-invasive

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Definition

• Mode: manner in which ventilator breaths are triggered, cycled, and limited

• Trigger: what the ventilator senses to initiate an assisted breath

• Cycle: factors that determine the end of inspiration

• Limit: operator-specified values

• Flow: Liters/min

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Positive end-expiratory pressure (PEEP)

• Prevent collapse of alveoli

• Improve oxygenation

• Intrinsic and Extrinsic PEEP

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Ventilator Modes

• Assist control mode ventilation (ACMV)

• Pressure-Control ventilation (PCV)

• Synchronized intermittent mandatory ventilation (SIMV)

• Continuous Positive Airway Pressure (CPAP)

• Pressure-support ventilation (PSV)

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Mode Independent Variables (Set by User)

Dependent Variables (Monitored by User)

Trigger/Cycle Limit

ACMV 

1. FIO2

2. Tidal volume3. Ventilator rate4. Level of PEEP5. Inspiratory flow pattern6. Peak inspiratory flow7. Pressure limit

1. Peak airway pressure, PaO2, PaCO2

2. Mean airway pressure3. I/E ratio

Patient/timer

Pressure limit

ACMV

From Harrison’s principles of internal medicine, table 252-1

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Advantages Disadvantages Initial Settings

1. Timer backup2. Patient-vent

synchrony3. Patient controls

minute ventilation

1. Not useful for weaning2. Potential for dangerou

s respiratory alkalosis(Tachypnea)

1. FIO2 = 1.02. Vt = 10–15 mL/k

g3. f= 12–15/min4. PEEP = 0–5 cmH

2O5. Inspiratory flow

= 60 L/min

ACMV

From Harrison’s principles of internal medicine, table 252-1

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ACMV

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Mode

Independent Variables (Set by User)

Dependent Variables (Monitored by User)

Trigger/Cycle Limit

PCV  1. FIO2

2. Inspiratory pressure level

3. Ventilator rate4. Level of PEEP5. Pressure limit6. I/E ratio

1.Tidal volume2. Flow rate,

pattern3. Minute

ventilation4. PaO2, PaCO2

Timer/patient

Timer/pressure limit

PCV

From Harrison’s principles of internal medicine, table 252-1

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Advantages Disadvantages Initial Settings

1. System pressures regulated

2. Useful for barotrauma treatment

3. Timer backup

1. Requires heavy sedation

(inverse I/E ratio when severe hypoxemia)

2. Not useful for weaning

FIO2= 1.0PC = 20–40 cmH2OPEEP = 5–10 cmH2Of= 12–15/minI/E = 0.7/1–4/1

PCV

From Harrison’s principles of internal medicine, table 252-1

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PCV

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Mode Independent Variables (Set by User)

Dependent Variables (Monitored by User)

Trigger/Cycle Limit

CPAP FIO2

Level of CPAP

Tidal volume

Rate, flow pattern

Airway pressure

PaO2, PaCO2

I/E ratio

No trigger

Pressure limit

CPAP

From Harrison’s principles of internal medicine, table 252-1

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Advantages Disadvantages

Initial Settings

Allows assessment of spontaneous function

Helps prevent atelectasis

No backup FIO2= 0.5–1.0b

CPAP = 5–15 cmH2O

CPAP

From Harrison’s principles of internal medicine, table 252-1

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CPAP

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Mode

Independent Variables (Set by User)

Dependent Variables (Monitored by User)

Trigger/Cycle Limit

PSV FIO2

Inspiratory pressure level

PEEPPressure limit

Same as for PCV + I/E ratio

Inspiratory flowPressure limit

PSV

From Harrison’s principles of internal medicine, table 252-1

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Advantages Disadvantages Initial Settings

Assures synchrony

Good for weaning

No timer backup FIO2= 0.5–1.0PS = 10–30 cmH2O5 cmH2O usually the level use

dPEEP = 0–5 cmH2O

PSV

From Harrison’s principles of internal medicine, table 252-1

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PSV

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Weaning from Mechanical Ventilator

• Discontinuation of mechanical ventilatory support

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Modes for Weaning

• SIMV

• PSV (8-10cmH2O)

• Spontaneous T-piece trial

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Factors in the weaning process

• Weaning parameters• Endotracheal tube• Arterial blood gases• Nutrition• Secretions• Neuromuscular factors• Obstruction of airways• Wakefulness

From Washington’s Manual, table 8-3

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Guidelines for assessing withdrawal of mechanical ventilation

• Patient’s mental status• PaO2 > 60mmHg with an FiO2 < 50%• PEEP < 5cmH2O• PaCO2 and pH acceptable• Spontaneous tidal volume > 5ml/kg• Vital capacity > 10ml/kg• MV < 10L/min

From Washington’s Manual, table 8-4

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Guidelines for assessing withdrawal of mechanical ventilation

• Pimax < -25cmH2O• Respiratory rate < 30/min• Static compliance > 30ml/ cmH2O

– Tidal Volume/ (plateau pressure – PEEP)– Static compliance reflects elasticity

• Rapid shallow breathing index (RSI) < 105 breaths/min/L– Ratio of Breathing frequency to Tidal volume

• Stable vital signs after one 1- to 2-hr spontaneous breathing trial

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THE END

Thanks for your attentions!