CPAP and NIV

Question 1

Non-invasive ventilation (NIV) and continuous positive airway pressure (CPAP) are forms of ventilatory support used in acute respiratory failure when a patient remains hypoxic despite optimisation of
medical management

what is NIV

Answer 1

NIV is a form of breathing support delivering air, usually with added oxygen, via a facemask by positive pressure, used in respiratory failure. The term NIV is often used interchangeably with the trade name BiPAP

NIV delivers differing air pressure depending on inspiration and expiration. The inspiratory positive airways pressure (iPAP) is higher than the expiratory positive airways pressure (ePAP).

Question 2

when is NIV/BiPaP used

Answer 2

In the acute setting, NIV is used in type 2 respiratory failure with respiratory acidosis (for example in a COPD exacerbation).

Question 3

what is CPaP

Answer 3

CPAP supplies constant fixed positive pressure throughout inspiration and expiration. keeps airways open. If delivered with oxygen, it can allow a higher degree of inspired oxygen than other oxygen masks.

Question 4

when is CPaP used

Answer 4

severe obstructive sleep apnoea (splinting the upper airway) and in the acute setting for type 1 respiratory failure, for example in acute pulmonary oedema (recruiting collapsed alveoli).

Question 5

indications for NIV

Answer 5

COPD with respiratory acidosis (pH <7.35)
Hypercapnic respiratory failure secondary to chest wall deformity (scoliosis, thoracoplasty) or neuromuscular disease
Weaning from tracheal intubation

Question 6

indications for CPAP

Answer 6

Indications for CPAP include:

Hypoxia in the context of chest wall trauma despite adequate anaesthesia and high flow oxygen (pneumothorax should be ruled out using a chest x-ray prior to commencing CPAP)
Cardiogenic pulmonary oedema
Pneumonia: as an interim measure before invasive ventilation or as a ceiling of treatment
Obstructive sleep apnoea

Question 7

contraindications for NIV or cPAP

Answer 7

Vomiting/excess secretions (aspiration risk)
Confusion/agitation*
Impaired consciousness*
Bowel obstruction*
Facial burns/trauma
Recent facial/upper gastrointestinal/upper airway surgery*
Inability to protect airway*
Pneumothorax (undrained)*

Question 8

complications of NIV and cPAP

Answer 8

If ePAP is set too high venous return can be impaired leading to hypotension.
If iPAP is set too high it can impair venous return, cause the mask to leak, reduce patient tolerance and cause stomach inflation increasing the risk of aspiration.
NIV can cause pressure sores due to the tight-fitting mask, particularly over the bridge of the nose.