Breath Flow Rate
December 11, 2017
After reviewing the many ways to treat Upper Airway Resistance Syndrome (UARS), it was clear that I needed a way to be able to monitor whether a particular treatment was helping. My plan is to try several different treatments one at a time. I needed a way to see how well a given treatment was working. As such, I started thinking about how best to go about collecting sleep data.
Although professional sleep studies can provide a lot of high quality data, they’re expensive and I don’t really like the travel and related inconvenience. One the other hand, there are much less expensive home sleep studies like the ones offered by AXG Sleep Diagnostics LLC that allow a person to monitor their sleep in their own bed. Still, the cost is several hundred dollars and I just don’t need the sort of professional analysis that these studies provide. I needed a way to inexpensively get a sense of my sleep quality that I could do myself. So what was it that I actually needed to monitor.
In Evaluating Sleep Study Data, I talk about the importance of monitoring breath flow rate. It’s really the all critical piece of data that a person wants to collect. If you can see the shape of the breath-by-breath flow rate curve, you pretty much know how well a person is breathing. You’ll know if their sleep disordered breathing has been addressed.
When I think about sleep studies in general, monitoring brain waves, chest/belly/leg movement, heart rate, and blood oxygen levels is more about quantifying the severity of the disordered breathing than anything else. Take a look at Sleep Jargon and read over the definitions of the various types of disordered breathing like hypopnea and apnea. If you’re going to score these types of events, you need to be monitoring other “channels” such as brain waves, chest/belly movement, and so on.
In my case, I just needed a way to be able to tell if a particular treatment was working. From my understanding, I just needed to be able to monitor breath flow rate. So I looked for a week to trying and find an inexpensive way to do this. If you read Additional Sleep Disorder Indicators, you know I’ve used an infrared camera with a microphone taped under my nose to monitor breathing. This is definitely an inexpensive way to get a pretty good sense for how a person is breathing. However, sleep expert, Dr. Krakow emphasizes the importance of smoothing out the breath flow rate. As such, I felt like I needed a better approach than a mic taped under my nose. I needed to be able to see the breath flow rate curves on a graph.
Alice PDx Type III HST
Eventually, I found a used, professional grade, home sleep study kits being sold on Amazon. Given that I didn’t know that I could simply use Sleepyhead Software to read and display various data including breath flow rate from my Positive Airway Pressure (PAP) machine, I purchased a used Alice PDx home sleep study system for $1,700. Yeah, I know. That’s a lot of money, but high quality sleep is important and I figured with the number of times I was going to be checking my sleep quality, that it would save me money and hassle in the long run. Besides, I wanted to check friends and family.
The basic Alice PDx is a Type III Home Sleep Test (HST). It measures breath flow rate, body position, chest/belly movement, heart rate, and blood oxygen levels. From this data, the Respironics Sleepware G3 software that comes with the device also displays graphs of PAP pressures, tidal volume, snoring, and total effort. Being a professional device, you can purchase and add on additional components to monitor channels such as brain waves and leg movement. The G3 Sleepware software is fairly complex in the number of factors that can be monitored and includes a suite for patient management.
In this Alice PDx trial, they conclude “In a population with a high suspicion of OSA (Obstructive Sleep Apnea), the Alice PDX showed a high level of diagnostic agreement with a simultaneous PSG (Polysomnogram/Lab Sleep Study)and performed valid home diagnostic studies for OSA. If manually scored, the portable device can be used by sleep specialists for diagnosing moderate-to-severe obstructive sleep apnea in cases with a high pretest probability for the disease over a wide range of disease severity. The technology can be deployed reliably outside of the sleep laboratory setting.”
Alice PDx Evaluation
After the device arrived and the excitement wore off, I struggled to figure out the basics on how to use the device. Granted, there are videos on line explaining to patients how to use the Alice PDx. However, there is virtually no information on how to transfer the data from the SD card in the Alice PDx into the Sleepware G3 software and then use this software to view and analyze the data.
It took me days to figure this out. I kept trying to use the data cable that connects directly between the Alice PDx and my computer USB port to transfer data. Little did I know, but this cable is primarily meant for configuring the type of data the device should record along with taking live, on-the-fly measurements, and I suppose calibrating and testing. Basically, it’s for telling the Alice PDx who the patient is and what channels it should record.
After two days, I finally figured out I needed to use a SD card reader that allowed me to directly plug the SD card into my PC to actually import the recorded data into the software. You simply remove the card from the Alice PDx, plug it into your PC, and click to Import. It seems obvious now but at the time, I was really befuddled by the software and data cable. I’m guessing there isn’t one other person that is going to go down this road so I’ll spare you other details like how to “Build a Channel Configuration” and so on. Note: While writing this article, I found this Sleepware G3 Quick Start Guide.
So while the Alice PDx did comes with very nice sleep data management and analysis software, Sleepware G3, it did not come with an instruction manual. For that, you can actually order a training DVD and replacement parts from various online medical vendors. However, I quickly learned that I actually needed a prescription for this.
I found this out the hard way when I went to order replacement cannulas. Amazingly, no one will even sell you a thin plastic tube (cannula) for the Alice PDx without a doctor’s prescription. Happily, I was able to purchase a whole box of new cannulas from a guy on eBay for a fraction of what they would have cost through a medical supplier. It took me quite a while researching what cannulas would actually work with the Alice PDx, as the Phillips Respironics catalog simply isn’t set up for the do-it-yourself types. After figuring out the catalog number, a simple Google search lead me to eBay suppliers.
However, I do worry about the tiny wires, belts, and finger sensor. If these break, I’ll have to go through a medical supplier. As such, my wife spoke to her nurse practitioner explaining that I’d purchased the device to monitor her sleep quality in order to determine if this was an issue for her. And I did in part. After all, many post-menopausal women suffer from sleep disordered breathing. We now have a script to purchase Alice PDx replacement parts and other accessories.
While I’m on the topic of discussing the negatives of the Alice PDx, I have to say that the breath flow rate is very coarsely measured. Compared to the smooth sinusoidal curves that I’ve seen recorded at the sleep lab and by reviewing PAP data from a Resmed VPAP machine using SleepyHead software, the Alice PDx graph of flow rate is very choppy. It abruptly rises up, stays high albeit with a jagged edge, and then abruptly drops down. From Evaluating Sleep Study Data, we know that this is not how breath flow rate graphs typically look.
Phillips Respironics Sleepware G3 Output
Now you might think to yourself that the used unit I purchased needs to be re-calibrated or is just downright failing. However, I’ve seen flow rate graphs from the Alice PDx displayed in the Sleepware G3 software, and it looked the same. So you can see the rate, relative amplitude, and get the calculate tidal volume, but it is very hard to get a sense for the quality of the breath from the Alice PDx. Given the importance of a smooth flow rate curve as discussed by Dr. Krakow, this is a real deficiency. Note: I may have had a faulty cannula or the flow rate curves may be different with and without PAP; I’ve still got some testing to do.
In addition to the course flow rate graphs, I also had issues with thesoftware installation and the hardware connectors. The software requires you to install Microsoft SQL Server in order to be able to store your sleep data on your computer. As I’m not very familiar with databases, this took me several attempts. Luckily, I always image my hard drive so when I got the Sleepware G3 install totally messed up, I simply blasted my last configuration onto my drive and five minutes later, I started over. If someone is really interested, here are my Sleepware G3 Install Notes.
The last issue I had with the Alice PDx was with the SD card and finger oximeter ports. Both of these connections on the Alice PDx rely on very tiny fingers of metal to make the electrical connection. On the SD card, they contact the metal touch pads. On the DB9 COM connector on the end of the finger oximeter cable, they contact the metal pins.
These are flimsy strips of metal that over time become permanently misshapen – the metal fatigues and they don’t make good contact. There are more robust ways to make these connections. For example, instead of tiny metal fingers that over time get slightly bent, an entire sleeve a metal can be used to contact the pins on a DB9 connector. The bottom line is that these connections are prone to intermittent failure with increasing use.
In fact, if you watch this Alice PDx Usage video, they show how the DB9 connection may need to be pressed back in place during the night. I’ll spare you the details, but I actually got so tired of having to wiggle the DB9 plug through out the night to keep it connected that I took the Alice PDx apart and made a very tiny tool to realign the contact fingers. I had to use a PC USB microscope with LED lighting because the work was so small. I know, it was a gutsy move but I really hate stuff that doesn’t work right. Anyway, it’s all good now.
The Alice PDx is a professional grade home sleep study (HST) device. The trial study above shows that is useful for detecting obstructed breathing. Except for the deficiencies noted, it is well made and definitely sophisticated. There are no less than three complex circuit boards packed inside the device. In addition, you can even purchase add-ons like an ECG Yoke to measure brain waves to change it from a Type III to a Type II device – although it is quite expensive.
Given that I will be trying several approaches to improving my sleep disordered breathing, I needed a way to be able to monitor sleep quality by myself. I don’t like guessing. Furthermore, I don’t have the time or money to pay for multiple sleep studies, even if they are the less expensive Type III studies – not to mention the necessity of getting a prescription.
The Alice PDx does a pretty good job. Although, there are some steep software learning curves, used hardware can be buggy, and the flow rate graphs are rather course. Nonetheless, if a person has the money and is planning on doing a lot of DIY treatments, it may be worth it to be able to do your own Type III Home Sleep Test (HST). Having said this, there are less expensive alternatives that actually do a better job monitoring breath flow rate – more in Sleep DIY Testing.
Note: As the Alice PDx is meant to be used by professionals only, don’t expect any support from the manufacturer.