Non-invasive ventilation (NIV) refers to systems which support gas exchange between the atmosphere and the lungs without the need for endotracheal intubation or tracheostomy.

The two main uses of NIV in acute medicine are:

• Management of acute type 2 respiratory failure (T2RF) complicating an exacerbation of chronic obstructive pulmonary disease (COPD) (Chapter 61; Figure 61.1), when it can reduce the need for invasive ventilation and improve survival.
• Management of patients with chronic T2RF maintained on home NIV presenting with worsening respiratory failure.

Less commonly, acute decompensated T2RF is the first presentation of chronic diseases causing T2RF (kyphoscoliosis, spinal injuries, neuromuscular diseases, e.g. motor neuron disease, or morbid obesity) and may require similar management with NIV.

Contraindications to the use of NIV are summarized in Table 113.1. When a relative contraindication is present, NIV may be considered on the ward, if invasive ventilation and ICU care is inappropriate.

NIV is often ineffective in treating severe hypoxaemia, as oxygen delivery is not controlled and depends on the pressure settings of the machine.

Non-Invasive Ventilation in Exacerbation of COPD

NIV should be considered for respiratory acidosis which persists despite maximal medical therapy given within 60 min of admission (pH 7.25–7.35, PaCO₂ >6 kPa (>45 mmHg)). The patient should be conscious and cooperative, and the treatment should be in keeping with the patient's wishes.

Immediate maximal medical therapy consists of:

• Salbutamol 2.5–5 mg by nebulizer
• Ipratropium 500 μgm by nebulizer
• Prednisolone 30 mg PO (hydrocortisone 100 mg IV if oral route not possible)
• Antibiotic therapy where indicated
• Controlled oxygen using a Venturi system (see Chapter 118)

Before starting NIV, a plan of management should be decided and documented, with consultant involvement. Options include:

• Requires immediate intubation and ventilation
• Suitable for NIV and suitable for escalation to intensive care treatment/intubation and ventilation if required
• Suitable for NIV but not suitable for escalation to intensive care treatment/intubation and ventilation
• Not suitable for NIV but for full active medical management
• Palliative care agreed as most appropriate management

Set-Up of Non-Invasive Ventilation

NIV should be prescribed by a doctor trained in the use of NIV, and delivered in a setting where it can be managed by experienced staff (e.g. nurses and NIV physiotherapists working in ICUs, HDUs, acute medical units or respiratory wards).

NIV typically refers to bi-level ventilation delivering two set pressures:

• IPAP: the inspiratory positive airways pressure that delivers the pressure support required to ventilate the patient
• EPAP: the expiratory positive airways pressure that recruits under-ventilated areas of the lungs and holds the airways open

The set-up of bilevel NIV is summarized in Table 113.2.

CPAP is another form of NIV that provides one fixed pressure and is used mainly to improve oxygenation in type 1 respiratory failure due to cardiogenic pulmonary oedema (Chapter 47).

Up to 30% of patients are unable to tolerate NIV; the set-up is crucial to its success. Time spent with the patient in the first 30 min helps to reassure the patient and prevents future problems.

Management of the Patient Receiving Non-Invasive Ventilation

Weaning of Non-Invasive Ventilation

Problems

Admissions in Patients on Long-Term Home NIV

Increasing numbers of patients are being cared for in the community with home NIV. It is important to review the ventilatory status as part of any admission in this group:

• Assess for symptoms of excessive daytime sleepiness (indicative of sleep fragmentation)
• Ask about early morning headaches (indicative of persisting hypercapnia)
• Enquire about snoring whilst on NIV (may suggest inadequate pressures to keep the upper airways patent)
• Check daytime arterial oxygen saturation: are the oxygen saturations < 92% on air?

These features may indicate inadequate treatment. Check arterial or capillary blood gases and seek specialist advice.

When admitted with unrelated problems, patients have occasionally had their NIV omitted in error. Ongoing NIV is crucial to prevent decompensation, and should be continued unless a contraindication has developed.

Use the patient's own NIV where possible. Inform the respiratory team/team responsible for their NIV therapy. In those who have presented with worsening/decompensated T2RF, both the respiratory and intensivecare teams should be involved as appropriate. The reasons for deterioration include:

• Presenting condition worsens respiratory function, for example pneumonia
• Decreased use of NIV prior to admission, for example because of vomiting
• NIV not tolerated
• NIV interface no longer adequate
• High mask leak
• Settings no longer adequate, for example following weight gain
• Worsening of underlying condition

Identify and treat the underlying cause and consider either increasing the hours of NIV usage or increasing the NIV pressure settings.

Many patients on NIV have a poor prognosis because of the underlying diagnosis:

• Check if they have advanced care plans
• Check current or previously expressed wishes about future treatments, such as 24 h-a-day NIV use, invasive ventilation and resuscitation
• Consider palliative care involvement
• NIV can be weaned in end-of-life care if wished by the patient and a protocol for weaning NIV in this setting should be followed