Setting the Vent & Problems

2 Aspects

• Oxygenation

• Ventilation

Initial Settings

• Set mandatory breaths – Pressure or Volume

• Set Assist & Trigger

• Set PEEP and FiO2

• Set Rate

• Set Inspiratory Time

• Set Alarms

• Mandatory Breaths– Pressure – Normal Lungs start about 20cmH2O then titrate to

desired tidal volume.– Volume – Based on IBW – Start at 8ml/kg

• Assist - If Mandatory breaths are Pressure controlled set as (Inspiratory Pressure – PEEP)

• Trigger - 2 (L/min)

• PEEP – Start at 5 if normal lungs, 10 if not

• Rate – 12 unless metabolic acidosis then 15-25

• Inspiratory Time – Go for I:E 1:2

What’s the problem…..?

Causes of High AWP

• Patient– Bronchospasm– Sputum Plug– Coughing

• Tube– Blocked– Bronchial Intubation– Biting

Hypoxaemia (Generally a PO2 of >8kPa is fine)

• Is this to do with the vent settings?

Things that are nothing to do with vent settings should be excluded

first.

• Tension Pneumothorax

• Collapse / Consolidation

• Cardiogenic / Non-Cardiogenic Pulmonary Oedema

Vent Settings

• Oxygenation is proportional to mean airway pressure so can be increased by:– Increasing the inspiratory pressure (keeping tidal

volume <10ml/kg or <7ml/kg if ARDS and plateau pressure <30cm H2O)

– Increasing PEEP– Increasing the inspiratory time (which ends up as

inverse ratio)

• Only if this doesn’t work should FiO2 be increased.

Respiratory Acidosis

• This should be treated to a pH of >7.25 by lowering the pCO2 towards normal.

• If there is also a metabolic acidosis a decision needs to be made on an individual patient basis.

• Hypercapnia is corrected by increasing rate or tidal volume.

Lung Protective Ventilation

• Ventilator induced damage to lungs causes the release of cytokines causing multi-organ failure.

• Possibly only an issue in ARDS

• ARDSnet trial (2000) – Ventilation at 12ml/kg (Pplat <50) vs 6ml/kg (Pplat <30) dropped mortality from approx 40 to 30% with lower Vt.

• ‘Permissive hypercapnia’ unles concerns such as a raised ICP.

Fighting the Ventilator

What does that mean?

Possible Causes

• Not enough sedation

• Not enough analgesia

• Airway obstruction

• Inappropriate vent settings

How would you assess and treat?

•Check vent settings – are you asking the patient to do something unreasonable?

•Check analgesia

•Check for tube blockage

•Assess respiratory system (is there a pneumothorax etc?)

•Would the patient be better spontaneously breathing (with assist)?

•Bolus of sedation

•Muscle relaxation is a last resort.

Ventilator Care Bundle

• Oral hygeine

• Supraglottic suction

• Cuff Pressure monitoring

• Stopping PPIs if no longer required

• Head elevation

• VTE prophylaxis

• Sedation holds (with a view to extubate)