GoodKnight 420G CPAP - Product Review

The Puritan Bennett GoodKnight 420G CPAP

A Subjective Product Review

©2004, 2007 by Steven K. Roberts
Nomadic Research Labs

(updated May, 2005 and Nov, 2006 and April, 2007)

At this writing, the smallest and lowest-power CPAP on the market, ideal for traveling sufferers of Obstructive Sleep Apnea (OSA)

DISCLAIMER: I have no experience with any other CPAP units, so this is not a comparative review.

When I was diagnosed in June 2004 with sleep apnea, my first thought was that a big, power-hungry "blower" would be completely incompatible with my upcoming Microship expedition. I immediately began looking into alternatives to the CPAP machine (Continuous Positive Airway Pressure) so that I would be free of bulky hardware. What I found, in short, is that the available surgeries are not only real "character builders," but also have disappointingly low success ratings (I heard numbers as low as 20%, with indications that a failed surgery can introduce new problems, including the inability to use a CPAP).

So I set out in search of the ideal machine for a nomadic lifestyle. Reading the alt.support.sleep-disorder archives (conveniently browsable at the talkabout site or through Google Groups) as well as nosing about the net with search terms like "low power CPAP," I soon discovered the GoodKnight 420 units from Puritan Bennett. The linked page describes the differences between their 420G entry-level unit, the 420S with compliance tracking, and the 420E auto-pap... but what they have in common is that they are small (2.9" X 5.6" X 7.7"), light (1.54 pounds), and low power (operating on a 12V DC supply).

Fortunately, I didn't need any of the more advanced features, so I settled on the 420G... quickly discovering that the price range was insane, ranging from under $300 from some of the online vendors to an absurd $2500 or even more if provided via a DME (Durable Medical Equipment) provider contracted through the sleep center. With my minimal health insurance, the choice was obvious... so I bought from CPAP Supplies Plus/Direct in Illinois and was very pleased with their service.

Note added Nov 24, 2006: I had occasion to deal with this company again while I was on a boat trip this past August. I fried my machine while in Canada, possibly due to an intermittent power connection to my 12-volt system. The cpapplus.com folks were absolutely heroic in getting me a new machine as fast as possible via International Fedex (even under warranty, with Puritan-Bennet's approval... even though the time had officially expired). At the same time, I bought another, just to have a backup of this essential life-support unit. I also picked up the new 2.5-ounce Resmed Mirage Swift nasal pillow mask, and it has displaced my trusty Conjo (which was in turn better than the more traditional masks I had used... though this "interface" choice is highly subjective).

I've had the unit for about 3 years now, and have been very impressed with its quiet operation and unobtrusive presence on my bedside table. It came with a zippered carrying case, and it's easy to pack along with the 12-volt wall wart, hose, and interface; I've taken it on overnight trips with no difficulty (I measured 500mA supply current at 6 cm pressure). This photo gives you an idea of its size and form factor, which is slightly fatter than a pair of VHS tapes stacked together:

GoodKnight 420G CPAP on bedside table

Operation is simple: when going to bed, just push a single button to turn it on. When first getting used to the hose-head life, you can use the "Ramp" function that slowly raises the pressure from 4 cm to the target value prescribed in your sleep study; there is a separate button for this. A maintenance menu allows tweaking these parameters, setting the clock, and observing total time used... and it's easy to get at the "secret" menu which allows setting the pressure. It's a pretty clean user interface, overall.

The 420G control panel

The only maintenance item on board is a small rectangle of filter foam over the air intake, which is easily rinsed out every week or so.

One thing I haven't tried yet, but is definitely required in some cold environments, is the use of a heated humidifier. Like any CPAP, this is compatible... a short jumper hose connects from the blower to the humidifier, then the long hose continues from that to the patient interface. The same company now has a unit mated to this machine.

At this point, I know of no other CPAP unit that would be anywhere near as well suited to traveling as this one, and can enthusiastically recommend it for that as well as standard home use. Good luck, and sleep well!


Brief Guide to the 420G Hidden Menu Go to hidden menu by simultaneously depressing the hidden button under the letters "Go" in the "GoodKnight" name and the Information Access button for one second. The first parameter shown is the pressure. Use ON/OFF (up) and Ramp (down) keys to adjust the value. Each time you press Information Access, it advances to the next setting. These are: Pressure Level Ramp time Starting ramp pressure Hour meter value Compliance meter value Offset of pressure sensor One more press of Information Access exits this parameter-setting mode. This information is from the publicly available PDF Practitioner and Home Care Provider Manual and is provided for your convenience. DO NOT meddle with your pressure settings unless you know what you are doing!

Additional Resources

The circadiana blog has an excellent article about sleep patterns.

If you need more information on sleep apnea, there are a number of good books available:

Here are some CPAP-related items (masks, hoses, accessories) currently on eBay: