Non Invasive Ventilation

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Introduction

Non-invasive ventilation (NIV) is a method of delivering ventilatory support without the need for an Artificial airway. It can eliminate the need for Intubation and maintain the patient's ability to communicate, cough and and swallow. The use of NIV in acute hospital settings and at home is on the rise.

Aims of NIV

• Improve oxygenation
• Improve ventilation
• Relieve Hypercapnea
• Reduce the Work of breathing
• Avert Intubation

Uses of NIV

• Acute respiratory failure
• Acute/Chronic Respiratory failure with or without OSA
• Respiratory insufficiency
• Nocturnal Hypoventilation
• End stage Cystic fibrosis awaiting transplant
• As an adjunct to airway clearance techniques

Indications

• Respiratory distress
• Failure to improve ABGs with standard treatment
• Inability to maintain SaO2 > 90%
• pH > 7.28 and pCO2 < 10
• Poor inspiratory effort/Tidal volume causing ineffective airway clearance

Contra-indications

• Facial trauma
• Morbidity
• Cardiovascular collapse
• Uncontrolled arhythmias
• Pneumothorax
• Bronchopleural fistula
• Inability to clear secretions

Equipment check list

• Bi-level positive airway pressure (BiPAP) generator
• Anti-bacterial filter
• Smooth bore tubing
• Exhalation port
• Face mask, spacer and headgear
• Oxygen tubing
• Heated humidifier and tubing (if required)
• Oximeter with integral recorder

Setting up the equipment

• Measure the patient for the mask
• Connect the headgear and spacer
• Connect all the components from the machine as far as the exhalation port
• Set Mode to "Spontaneous/timed (S/T)"
• Set IPAP to 6cm initially
• Set EPAP to lowest default setting (2cm or 4cm, depending on the machine being used)
• Have all of this done before bringing the machine to the patient
• Discuss the target settings with the rest of the team, as well as whether supplemental oxygen is required

Explanation to the patient

• This will HELP your breathing, it will NOT control your breathing
• It will reduce the effort of breathing
• It will improve your oxygen level
• You will still be able to communicate, drink and cough
• We will try it for a short period of time at first and I will stay with you while you get used to it
• You will feel a rush of air initially but try a few breaths of varying lengths and you will realise that you control the machine and not the other way around
• We will start at low pressure - feel it on your hand
• When you have adjusted to it, you will feel more comfortable and may fall asleep

Sequence

• Fit and adjust the nasal mask and headgear - do not overtighten and draw the skin out from under the mask to improve the seal
• Check the oximeter readings and leave the oximeter on the patient
• Turn the machine on and connect it to the patient
• Encourage the patient to adjust breathing as per the instructions given above
• If oxygen saturation improves, ensure that the patient is aware as this will encourage compliance

Parameters

• EPAP - range from 2/4cm to 20cm depending on the model. Acts like PEEP, which serves to increase FRC
• IPAP - range from 2cm to 30 cm. Rarely effective below 12cm. Must be individualised.
• BPM - range from 4bpm to 30 bpm. On S/T mode, set the baseline to 12bpm
• IPAP - used only with Timed mode (not used at ward level, mainly in ICU)

Settings

• Establish target settings in consultation with the rest of the team before going to the bedside.
• When the patient is comfortable at 6cm, start moving the settings in 2cm increments until the target settings are reached.
• Review when the target settings are attained and if the desired gas exchange has not been achieved, discuss supplemental oxygen or respiratory stimulant with the team. If there is still no improvement, the patient may need Intubation.
• In the non-acute patient there should be signs of improvement within 2 hours of initiation of NIV.
• Complete the patient record and leave it at the bedside along with an Instruction sheet.
• Discuss with the nursing staff before leaving.

Troubleshooting

• Nasal dryness or rhinorrhoea - add a humidifier
• Bloating or belching - try sips of peppermint water
• Soreness on the bridge of the nose - use a triangle of Granuflex

Suggested reading

• eMedicine.com article on Non-invasive ventilation

Sources

• NIV Guidelines, Physiotherapy Department, St. Vincent's University Hospital, Ireland (2001)
• eMedicine.com article on Non-invasive ventilation