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Respiratory failure

Indications for ventilation in respiratory failure

This is a difficult decision and should always take place in consultation with a senior doctor. If the patient is causing you or the referring medical or nursing staff significant worry, discuss with your seniors immediately.

 

Indications for ventilation

Hypoxaemia

Hypercarbia

Exhaustion

Increase in work of Breathing

 

The non-invasive methods of respiratory support described below are useful if the patient is likely to respond quickly (e.g. LVF, acute exacerbation of COPD). If the patient is in respiratory failure because of an illness that is likely to be prolonged (e.g. ARDS, pneumonia) then invasive ventilation is usually more appropriate.

CPAP

This is the application of continuous positive pressure to the patient's respiratory system. It normally refers to the non invasive application of a tight fitting mask that is connected to an oxygen delivery system which has an outlet valve (or something similar). This valve allows the build up of pressure especially on expiration. The tight fitting mask is essential to maintain the positive pressure. A hood that covers the patient's head is also in use and can be more comfortable than a face mask.

Pressures usually employed are between 5 and 10 cm of H2O.

CPAP is usually used to improve oxygenation not to treat hypercarbia.

Continuous Positive Airway Pressure (CPAP) is an extremely useful technique for some forms of respiratory failure. CPAP systems can deliver high FiO2. CPAP works particularly well for cardiogenic pulmonary oedema and can allow time for medical therapy to work. It may also help in ARDS. The effect is more variable in other forms of respiratory failure.

Non-Invasive Ventilation (NIV)

Usually refers to the application of positive pressure ventilation in a non invasive way. This is achieved by using a tight fitting face mask and a ventilator that is capable of of delivering two levels of pressure; inspiratory (high pressure e.g. 8 cm H2O) and expiratory (lower pressure e.g. 4 cm H2O).

If the inspiratory and expiratory pressures are similar, this is not called NIV; it is called CPAP.

NIV is usually used to improve oxygenation and increase minute volume, thus reducing PaCO2.

Patients with hypercapnic, acidotic exacerbations of COPD should be offered Non Invasive Ventilation (NIV) on the medical wards at an early stage in the illness. This reduces mortality and the need for intubation. Most NIV equipment cannot deliver high FIO2.

Think about NIV When called to see any patient with respiratory failure. Beware that if the patient is in distress then NIV is not appropriate. In this case the correct course of action would be to proceed to invasive ventilation as soon as possible. Always discuss with your senior cover.

If the underlying disease is not likely to resolve quickly (e.g. pneumonia) and the patient becomes dependent on NIV, then invasive ventilation is likely to be the best option. This is because this group of patients do not tolerate even short periods without NIV. This will make it difficult to deliver other aspects of patient care e.g. feeding, drinking, mouth care..etc. This is different to COPD patients with acute exacerbations, as they can normally tolerate a few minutes off NIV to eat or drink.

 

CONTRAINDICATIONS TO NIV

Coma (except in CO2 narcosis when a short trial of NIV might be attempted by an experienced clinician)

Need for airway protection

Agitation/delirium

Facial & anatomical abnormalities

Recent upper GI surgery with anastomosis

Patient refusal

 

 

NIV can also be used as a bridge to invasive ventilation, but always discuss with your senior cover.

 

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