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Bi-level ventilators, also known by the trade name BiPAP®, are non-invasive ventilators that alternate between a high and low pressure to facilitate breathing.
Bi-level ventilators are capable of facilitating respiration in an individual that has almost zero ability to breathe on their own. However, in the case of ALS, spasticity (stiffness) of the diaphragm muscle may prevent sufficient respiration from occurring, even with the use of a bi-level machine that is configured to provide a great deal of support.
Bi-level ventilators are not strictly considered to be life-saving devices, however, it is possible for the user to be so dependent upon its function that they could lose their life if it were to fail or if they were to lose access to it.
Bi-level ventilators are typically only used at times of day when breathing difficulties are being encountered. Often, these difficulties are most pronounced when lying down. As a result, overnight use tends to be the most common time when the ventilator sees regular use.
The feeling of a ventilator can be challenging to adjust to, so it’s advisable to become accustomed to it during the day before trying to use it overnight.
Usage of the ventilator will increase as breathing difficulties worsen. Daytime use on an as-needed basis typically follows a period of only using it overnight. Eventually, the ventilator may be used constantly except for brief periods such as speaking, when consuming food, or maintaining oral hygiene.
Bi-level ventilators are fitted with heated water humidifiers to increase comfort for the user. Distilled water is recommended, however, clean municipal water may be used temporarily.
Water that is not distilled may cause boiler scale (calcium deposits) to form inside the reservoir.
Bi-level ventilators are designed to tolerate a modest amount of leakage in the hose and at the mask fitment interface. However, excessive leakage will negatively affect operation. The ventilator will compensate for leakage by increasing the flow volume; this may produce a feeling of having one's face in a strong breeze. Breathing is uncomfortable in this circumstance and can be challenging. If the leak is extreme, inadequate flow of air into the lungs will result, and the machine will trigger an alarm.
Leakage is usually easy to hear and feel; checking for leaks and attempting to mitigate them is prudent, especially before having the ventilator's settings changed.
The ventilator should be within reach of the user whenever possible.
The ventilator should always be placed at an elevation that is slightly lower than the user's head. The water reservoir in the machine may leak in some circumstances; having the user's head slightly higher reduces the risk of ingesting water through the vent tube.
The hose that connects the mask to the machine should be free of twists or kinks, and should be easy to move. It should be possible for the user to lie on either their right side or left side in bed, without the hose being under any tension. Leakage at the mask may occur if the hose becomes taught when lying in a certain position; in extreme circumstances, the mask may come right off.