What is Non-Invasive Ventilation?
Non-invasive ventilation (NIV) refers to the administration of mechanical ventilation to the lungs using methods such as a face mask, without the need of an invasive artificial airway, such as an endotracheal tube (ETT) or tracheal tube (TT).
Invasive ventilation is application of mechanical ventilation via an endotracheal or tracheotomy tube.
Non-invasive ventilation has been used as an alternative to invasive mechanical ventilation (being placed on a ventilator) for people with respiratory failure or chronic respiratory insufficiency who can no longer breathe adequately on their own. In acute settings, NIV delivers effective therapy with less risk of infection and improved survival in patients with respiratory failure.
The growing use of non-invasive ventilation over the last 2 decades to treat respiratory distress has made NIV an integral part in the management of both acute and chronic respiratory failure, in both the home setting and in the hospital setting. The flexibility and comfort offered by non-invasive ventilation make it a valuable addition in the management of patients with respiratory failure.
Main Types of Non-Invasive Ventilation
There are two main types of non-invasive ventilation; positive-pressure and negative-pressure non-invasive ventilation.
In positive pressure non-invasive ventilation, positive pressure is applied to the airway to inflate the lungs directly through a nasal mask, face mask, or nasal plugs. It is the most commonly used non-invasive ventilator mode in the intensive care unit (ICU). CPAP (continuous positive airway pressure) and BiPAP (Bilevel Positive Airway Pressure) are the most common examples of positive-pressure ventilation.
In negative-pressure non-invasive ventilation, negative pressure is applied to the thorax and abdomen to draw air into the lungs through the upper airway using a device that encases the thoracic cage starting from the neck, with devices ranging from a whole-body tank to a cuirass shell. Iron lung or tank ventilator is the most common example of a negative-pressure ventilator.
Indications and Contraindications for Non-Invasive Ventilation
Some of the common indications for non-invasive ventilation include:
- Chronic obstructive pulmonary disease (COPD)
- Acute asthma exacerbation
- Immunocompromised patients
- Acute cardiogenic pulmonary oedema
- Acute respiratory failure
- Decompensated heart failure
- Palliative care
- Acute deterioration of disorders associated with sleep hypoventilation
Some of the common contraindications for non-invasive ventilation include:
- Respiratory or cardiac arrest
- Facial surgery, trauma, or deformity
- Untreated pneumothorax
- Haemodynamic instability
- Inability to protect airway or clear secretions
- Agitated or uncooperative
Eligibility Criteria for Non-Invasive Ventilation
Some of the criteria that need to be fulfilled prior to beginning NIV treatment include:
- Ability to protect his or her airway
- Adequate level of consciousness, with the exception of hypercapnic COPD patients
- Expected level of compliance with non-invasive interface
- Ability to manage respiratory secretions
- Ability to recover to a quality of life of acceptable standard
Failure to fulfil any one of these criteria contributes to the patient being considered ineligible for NIV.
Mechanisms of Action of Non-invasive Ventilation
The favourable effects of non-invasive ventilation in patients with acute respiratory distress include:
- Reduction in inspiratory muscle work and avoidance of respiratory muscle fatigue
- Increases the volume of air moved into and out of the lungs during each breathing cycle
- CPAP counterbalances the energy expended to inhale and exhale a breathing gas by delivering constant and steady air pressure by keeping the airways continuously open
- NIV improves respiratory system compliance by reversing microatelectasis (complete or partial collapse of the lung)
- Enhances cardiovascular function
Benefits of Non-Invasive Ventilation
Some of the benefits of non-invasive ventilation when compared with invasive ventilation include:
- Prevents resistive work of breathing imposed by an endotracheal tube
- Prevents complications associated with endotracheal tube intubation, such as aspiration, trauma, and injury to the trachea, larynx, or hypopharynx
- Decreases infectious complications, such as pneumonia, sepsis, or sinusitis
- Enhances patient comfort
- Decreases the need for sedation
- Allows intermittent use
- Protects speech, swallowing, and expectoration
- Flexibility in wearing and removing mechanical ventilation
- Less cost
Risks and Complications of Non-Invasive Ventilation
Some of the risks and complications associated with non-invasive ventilation include:
- Gastric distension
- Facial skin necrosis
- Air leakage through mask
- Eye irritation
- Transient hypoxemia (abnormally low level of oxygen in the blood)
- Lack of airway access and protection
- Increased initial time engagement
- Delayed correction of gas exchange irregularity