Non-invasive Ventilation

Dr Liam Doherty,Consultant Respiratory Physician,Bon Secours, Cork

Positive Airway Pressure

CPAP = continuous positive airway pressure

BiPAP = Bilevel positive airway pressure = Inspiratory pressure (IPAP)

and expiratory pressure (EPAP)

Why?

Invasive ventilation

SedatedCan’t speakCan’t eatHigh infection riskIncreased bleeding riskBarotraumaLimited ICU beds

Non-invasive ventilation

Not sedatedCan speakCan eatLow infection riskAvailable on well-supervised medical wards

How does it work?

In summary

Stents airway

Recruitment of alveoli

Decreases right to left intrapulmonary shunting

Decreases work of breathing

Overcomes PEEPi

Lowers left ventricular transmural pressure reducing afterload and increasing cardiac output

Who gets NIV?

Acute Type 2 Respiratory failure

COPD, pH <7.35 despite maximum Rx on controlled O2Cardiogenic pulmonary oedema with hypoxia. Decompensated obstructive sleep apnoea. Chest wall trauma who remain hypoxic. (CPAP)Diffuse pneumonia who remain hypoxic despite maximum Rx (CPAP)Weaning from invasive ventilation.

Who can’t have NIV?

Recent facial or upper airway/upper GI surgery, Facial burns or trauma, Fixed obstruction of the upper airway, Vomiting.Inability to protect the airway, Copious respiratory secretionsLife threatening hypoxaemia, Severe co-morbidity, Confusion/agitation, Bowel obstruction.

Which ventilator

Types of NIV

Negative pressure ventilation e.g. “iron-lung”, tank, shell, cuirass, rocking bed,

pneumo-belt

Positive pressure ventilation Pressure limited (CPAP, Bilevel PAP) Volume limited

N.B. Diaphragm-pacing, glosso-pharyngeal breathing,

cough insufflator-exsufflator

Which interface

How do you commence NIV?

Monitoring progress

OximetryRespiratory ratePatient comfortPCO2

Patient-ventilator synchronisation

Give breaks for drinks/foodKeep on for as long as possible (2 days+)

When things go wrong!

Is ventilation inadequate?

Observe chest expansion

Increase target pressure (or IPAP) or volume

Consider increasing inspiratory time

Consider increasing respiratory rate (to increase minute ventilation)

Consider a different mode of ventilation/ventilator, if available

Is the patient synchronising with the ventilator?

Observe patient

Adjust rate and/or IE ratio (with assist/control)

Check inspiratory trigger (if adjustable)

Check expiratory trigger (if adjustable)

Consider increasing EPAP (with bi-level pressure support in COPD)

Downside to NIV

Horrendous to wear

Can’t talk

Can’t eat/drink

Can’t sleep

Agitation, claustrophobia

Poor synchrony

Delays intubation

Final messages

Give appropriate oxygen!

Non-invasive ventilators just blow air

Try to synchronise ventilator to patient i.e. ventilator should support normal ventilation

When in doubt use CPAP

NIV doesn’t work for everyone

(30% failure rate)

Never forget need for intubation!