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

2 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.

3 Indications for Mechanical Ventilator Hypoxemic respiratory failure: PaO 2 60% Hypercapnic respiratory failure: pH 50mmHg Respiratory rate > 35/min Others

4 Types of Mechanical Ventilator Positive pressure vs. Negative pressure Invasive vs. Non-invasive

5 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

6 Positive end-expiratory pressure (PEEP) Prevent collapse of alveoli Improve oxygenation Intrinsic and Extrinsic PEEP

7

8 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)

9 ModeIndependent Variables (Set by User) Dependent Variables (Monitored by User) Trigger/Cycle Limit ACMV 1. FI O2 2. Tidal volume 3. Ventilator rate 4. Level of PEEP 5. Inspiratory flow pattern 6. Peak inspiratory flow 7. Pressure limit 1. Peak airway pressure, Pa O2, Pa CO2 2. Mean airway pressure 3. I/E ratio Patient/timer Pressure limit ACMV From Harrison’s principles of internal medicine, table 252-1

10 AdvantagesDisadvantagesInitial Settings 1. Timer backup 2. Patient-vent synchrony 3. Patient controls minute ventilation 1. Not useful for weaning 2. Potential for dangerous respiratory alkalosis (Tachypnea) 1. FI O2 = V t = 10 – 15 mL/kg 3. f= 12 – 15/min 4. PEEP = 0 – 5 cmH 2 O 5. Inspiratory flow = 60 L/min ACMV From Harrison’s principles of internal medicine, table 252-1

11 ACMV

12 ModeIndependent Variables (Set by User) Dependent Variables (Monitore d by User) Trigger/Cycle Limit PCV 1. FI O2 2. Inspiratory pressure level 3. Ventilator rate 4. Level of PEEP 5. Pressure limit 6. I/E ratio 1.Tidal volume 2. Flow rate, pattern 3. Minute ventilation 4. Pa O2, Pa CO2 Timer/patient Timer/pressure limit PCV From Harrison’s principles of internal medicine, table 252-1

13 AdvantagesDisadvantagesInitial 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 FI O2 = 1.0 PC = 20 – 40 cmH 2 O PEEP = 5 – 10 cmH 2 O f= 12 – 15/min I/E = 0.7/1 – 4/1 PCV From Harrison’s principles of internal medicine, table 252-1

14 PCV

15 ModeIndependent 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

16 AdvantagesDisadvantage s Initial Settings Allows assessment of spontaneous function Helps prevent atelectasis No backupFIO2= 0.5–1.0b CPAP = 5–15 cmH2O CPAP From Harrison’s principles of internal medicine, table 252-1

17 CPAP

18 ModeIndependent Variables (Set by User) Dependent Variables (Monitored by User) Trigger/Cycle Limit PSVFI O2 Inspiratory pressure level PEEP Pressure limit Same as for PCV + I/E ratio Inspiratory flow Pressure limit PSV From Harrison’s principles of internal medicine, table 252-1

19 AdvantagesDisadvantagesInitial Settings Assures synchrony Good for weaning No timer backupFI O2 = 0.5 – 1.0 PS = 10 – 30 cmH 2 O 5 cmH 2 O usually the level used PEEP = 0 – 5 cmH 2 O PSV From Harrison’s principles of internal medicine, table 252-1

20 PSV

21 Weaning from Mechanical Ventilator Discontinuation of mechanical ventilatory support

22 Modes for Weaning SIMV PSV (8-10cmH 2 O) Spontaneous T-piece trial

23 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

24 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

25 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

26 THE END Thanks for your attentions!