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
Sedated
Can’t speak
Can’t eat
High infection risk
Increased bleeding
risk
Barotrauma
Limited ICU beds
Non-invasive ventilation
Not sedated
Can speak
Can eat
Low infection risk
Available on wellsupervised 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 O2
Cardiogenic 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 secretions
Life 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
Oximetry
Respiratory rate
Patient comfort
PCO2
Patient-ventilator synchronisation
Give breaks for drinks/food
Keep 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!