ALS From Both Sides, ALS Patient Care
By Diane Huberty, Retired RN, Certified Neuro Nurse
...and ALS Patient

Is it NIV, Bi-Level, BiPAP, AVAP or a Ventilator?

Any machine used to move air into the lungs is a ventilator. Some measure each breath given by the pressure, others by the volume, so a ventilator can be categorized as a pressure or a volume ventilator. That means diddly to an ALS patient having trouble breathing. What we care about is whether the air is delivered with a mask or requires a tube inserted into the airway. That categorizes ventilators into Non-Invasive Ventilation (NIV) with a mask, and Invasive Ventilation through an airway tube. Invasive ventilators don't have an abbreviation because for many years they were the only ventilators. They are commonly referred to simply as a vent.


The first NIV machine was the Iron Lung which used negative air pressure to lift the rib cage and draw air in. The Iron Lung isn't used today but there are vest sized machines that still use negative pressure.

NIV machines using Positive Airway Pressure (PAP) were developed in the 1980s to help people with sleep apnea, a condition where the airway collapses during sleep causing the person to stop breathing repeatedly. By pushing air directly into the lungs through a mask worn over the nose, the machine keeps the airway inflated so it won't collapse. This is CPAP, Continuous Positive Airway Pressure. It is not the correct NIV for people with ALS because the constant pressure makes it difficult to exhale when abdominal muscles are weak. The result is a feeling of suffocation which is no improvement over not being able to inhale without the machine! If your doctor is recommending a CPAP machine, it is definitely time to see a Pulmonologist familiar with ALS.

BiPAPIn the 1990s computer technology added a new dimension to NIV. Now the machine could push air in until a preset pressure was reached, then reduce the pressure to allow the person to exhale easily. Repeating this cycle made breathing more comfortable and suitable for people with neuromuscular diseases who could not exhale against the higher pressure. This type of machine was sold by Respironics using the brand name BiPAP (Bi-Level Positive Airway Pressure). Like the patented brand names "Kleenex" and "Band-Aide", BiPAP has become the common name for all such products even though there are other brands of Bi-Level machines.

A typical Bi-Level machine's settings are limited to

Bi-Level machines continue to become more advanced and make important changes in respiratory care. Like CPAP, Bi-Level machines were developed for home use but are increasingly used in Emergency Departments, during procedures, and even in Intensive Care. Computer technology has added the ability to store details of use in newer machines which can help in adjusting settings for optimal use. This information can be brought up on the machine's viewer or using an SD memory card. Another change to newer Bi-Level machines is that nearly all now have alarms to alert caregivers to problems in delivering air. A change that is slowly coming is the addition of an internal battery. Without an internal battery, the machine has to plugged in or be connected to an external battery to run. The use of external lithium battery packs has made them more portable than lugging around a car battery sized battery. A few Bi-Levels do have an internal battery that can power it for up to 5 hours.

The newest innovation in NIV is AVAP (Average Volume Assured Pressure Support) In the past, Bi-Level machines relied entirely on pressure to deliver the amount of air per breath. Volume monitoring was previously only available on Vents. AVAPS continuously detects the volume of air in each breath, averages it, and adjusts the amount of pressure gradually to assure the patient receives the right volume of air. Because the changes are adjusted whenever needed and are gradually applied, they aren't noticed by the user. Air leaks are adjusted for as well as changing masks and altitude changes. Like some other Bi-Levels, it can be set to gradually ramp up to its settings when you first put it on. All of this adds up to significantly more comfort as well as better control of CO2 levels.

Invasive Ventilators

There are several critical distinctions between NIV and an Invasive Ventilator:

One final comparison between NIV and invasive ventilation is the warning that a invasively ventilated person requires 24/7 care. That is true and yet misleading.

HomeVentGuide.pdf is an excellent resource on all the types of ventilation devices. It shows those available in different parts of the world and the settings, size, weight, power source, and alarms on each type and brand.

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