We left off with a patient who would have developed central apneas while using other forms of PAP such as CPAP or BPAP and thus might qualify for the diagnosis of complex sleep apnea or CompSA. These patients often benefit from a switch to adaptive servo-ventilation devices or ASV, which functions like bilevel in that a dual pressure system provides higher levels of air pressure on inhalation and lower levels on exhalation.
ASV also has some additional features that may be differ for different brands. We use mostly the RESMED ASV devices. In general, ASV attempts to gauge the volume of breath that is most natural to the patient, after which it attempts to deliver 90% or more of that “natural” breath. However, it also has a back-up rate feature in which it continuously insures delivery of the air volume let’s say 14 times in a minute or say 20 times in a minute as two examples.
In the course of the night, the volume of air needed can change just as the rate of respiration can change. If you start to breathe slower or faster, the ASV device will adjust accordingly. This capacity to make changes maintains an airflow sensation that feels very natural to most people who are regular users of the ASV device. Indeed, from most ASV users and more so than with any other type of PAP therapy device, I hear the unusual comment, “sometimes I cannot even detect the machine is doing anything because it feels so natural to breathe with ASV, especially compared to when I tried CPAP.”
However, getting used to the ASV delivery of pressurized air is somewhat distinctive, especially compared to every other form of PAP. The main distinction is that ASV’s back up rate initially may provoke a stronger sense of being controlled by the machine, because the machine really does have the ability to “force” a breath upon you. As you may know if you were using CPAP or BPAP or APAP and as an experiment you chose to hold your breath, you would notice the machine stops delivering pressurized air. But, with ASV, if you held your breath, the machine would still send a new “breath of air” at the most recently detected respiratory rate.
Nonetheless, the “secret” to rapid adjustment to an ASV device is to stabilize your own breathing (we’re not talking about synchronizing your breathing to the machine) by taking regular but more shallow breaths for the first few minutes when initiating use of the device. By doing so, the ASV device detects a specific volume of air and responds by delivering the 90% or so of that volume back to the patient. As this process unfolds, the individual usually notices nothing overwhelming about the pressurized air.
Now, consider the opposite scenario in an individual with anxiety, panic or claustrophobia. Because of his or her erratic breathing pattern, the volume of each breath will likely differ and in all likelihood in a wide range. The machine is likely to response in a wide range as well, and suddenly this type of patient may experience a “blow-out” effect in which the volume delivered was fairly huge and quite startling to the patient. When this effect occurs, most patients are awake and currently trying to fall asleep, but the overwhelming sensation of too much air thwarts efforts to adjust to the device let alone fall asleep.
To reiterate, when you put the mask on, for the first few minutes breathe in with less depth to each breath, in other words, more shallowly. It may or may not matter how fast you breathe. When you try this technique, some people breathe slower, some might breathe a bit faster, but the secret is to breathe more shallowly, which keeps the machine from delivering too much airflow back at you.
There is a second set of benefits from breathing more shallowly, and these benefits derives from what we discussed about carbon dioxide in Part III. By breathing shallowly, you will not push out too much carbon dioxide like someone who hyperventilates. Thus, you now have a stronger drive to breathe with the slight build-up of carbon dioxide in your system. And, by strengthening your respiratory drive, you are more unlikely to develop central apneas or engage in an erratic breathing pattern. Also, by following this step to breathe shallowly, many people report falling asleep very rapidly when using the ASV device. Last, of course, this entire process prevents the wild or erratic swings in breathing, which could have thwarted the capacity for the machine to function properly.
Remarkably, many cases—anywhere from 70 to 90% patients attempting ASV—end up using the device regularly. Notably, most of these patients at our center were individuals with the worst insomnia or mental health problems, which previously had caused them to struggle bitterly in their efforts to use other PAP devices. ASV turned into a godsend for these vulnerable patients.
As I mentioned previously, I am certain there are very successful and effective HST models in the practice of sleep medicine. Nonetheless, I maintain that learning to apply advanced technologies especially the ASV modality to patients with insomnia and related mental health issues serves not just as viable option but in many cases the only option.