IPPV - failure to tolerate ventilation

Agitation or ‘fighting the ventilator’ may occur at any time. If paralysed or heavily sedated, poor ventilator tolerance may be indicated by hypoxaemia, hypercapnia, ventilator alarms, or cardiovascular instability. The first priority is to assess the patient.

• Is the patient cyanosed?

• Is the chest moving?

• Are breath sounds present and equal?

• Are there abnormal breath sounds?

• Has the SpO2 changed?

Basic clinical assessment is necessary to judge how serious the problem is and whether immediate resuscitative steps are required. If the problem is serious, the first response must be to disconnect the ventilator and manually ventilate.

Manual ventilation with 100% O2 and a non-rebreathing bag allows assessment of how difficult it is to inflate the lungs, how long exhalation

takes, and whether the problem with ventilation relates to patient (problem persists) or ventilator (problem resolved) factors.

Poor initial tolerance

• Increase FIO2 to 1.0 and start manual ventilation.

• Check endotracheal tube is correctly positioned and both lungs are being inflated. Consider tube replacement, intra-tracheal obstruction,

pneumothorax, or bronchospasm.

• Check ventilator circuit is both intact and patent, and ventilator is functioning correctly. Check ventilator settings, including FIO2, PEEP,

I:E ratio, set tidal volume, respiratory rate, and/or pressure control. Check ‘pressure limit’ settings as these may be set too low causing

ventilator to cycle to expiration prematurely.

Poor tolerance after previous good tolerance

If agitation occurs in a patient who has previously tolerated mechanical ventilation, either the patient’s condition has deteriorated, or there is a problem in the ventilator circuit (including artifi cial airway) or the ventilator itself.

• The patient should be removed from the ventilator and placed on manual ventilation with 100% O2 while the problem is resolved. Resorting to increased sedation 9 muscle relaxation in this circumstance is dangerous until the cause is understood.

• Check patency of the endotracheal tube (e.g. with a suction catheter) and re-intubate if in doubt.

• Consider chest X-ray to identify endotracheal tube malposition (e.g. cuff above vocal cords, tip at carina, tube in main bronchus).

• Seek and treat changes in the patient’s condition, e.g. bronchospasm, tension pneumothorax, sputum plug, pain, raised intra-abdominal

pressure, pulmonary oedema.

• Where patients are making spontaneous respiratory effort, consider increasing pressure support or adding mandatory breaths.

• If patients fail to synchronise with IMV by stacking spontaneous and mandatory breaths, increasing pressure support and reducing

mandatory rate may help. Use of pressure support ventilation may also be appropriate.