How NIV improves ventilation

In this video from our Noninvasive Ventilation Masterclass course, we'll review the mechanisms by which NIV can improve ventilation and how this is achieved without directly influencing respiratory rate.

Noninvasive ventilation (NIV) is a powerful therapy that clinicians can add to their ventilation toolboxes. This course will cover the indications for NIV, initiation and optimization, how to monitor patients on NIV, and how to wean them from it. We’ll delve into the controversial uses of NIV, when NIV is a first-line therapy, and how to rationally test its effectiveness in these situations.

Noninvasive ventilatory support

[00:00]
You might think given the name, noninvasive ventilation, that this form of respiratory support is designed to improve the patient's ventilation. It certainly can improve gas exchange in a variety of pulmonary diseases. Ventilation refers to the exchange of oxygen for carbon dioxide. 

Minute ventilation: respiratory rate and tidal volume

[00:22]
The minute ventilation of the respiratory system is the amount of air moved in and out by a patient in one minute. It's defined as the respiratory rate times the tidal volume. The tidal volume is the volume of air inspired with each breath.

Spontaneous ventilation

[00:38]
Noninvasive ventilation is most commonly delivered as a spontaneous mode of ventilation. This means that patients control their intrinsic respiratory rate and the ventilator does not provide a minimum respiratory rate outside of emergency backup modes.

How noninvasive ventilation improves ventilation

[00:54]
We know that noninvasive ventilation improves patients' ventilation. But since it does not directly influence the respiratory rate, it must exert its effect on the tidal volume. Noninvasive ventilation allows an efficiency of breathing and the added pressure during inspiration augments the volume of air that is inspired, i.e. the tidal volume.

How noninvasive ventilation increases tidal volume

[01:15]
Increases in tidal volume improve ventilation of the entire lung. Another method of improving ventilation relates to the intrinsic pressure created by the airways at the end of expiration, which is termed intrinsic positive end expiratory pressure, or intrinsic PEEP.

Intrinsic PEEP and carbon dioxide exchange

[01:34]
In some disease states, the airway may be constricted making it more difficult for air and carbon dioxide to be released during expiration, and this results in hyper-inflated alveoli. Noninvasive ventilation can counteract this pressure to allow improved exploration. When the PEEP from the NIV ventilator is able to allow intrinsic pressure, that is intrinsic PEEP, from the alveoli to escape, there is improvement in ventilation and in carbon dioxide exchange.

So there you have it. The physiology behind how noninvasive ventilation can improve your patients' ventilation.