Nellcor N-395 Pulse Oximeter

snork1 wrote: . . . luckily the hardware designer was more together than the software guy.

You knew he would be, didn't you? Hardware designers always get the job done. Software guys, well . . ., they always just seem to quit when time runs out, regardless of whether they're done or not. .

snork1 wrote: . . . it also won't tell me when the funky connector disconnects . . .

Ya know duck tape can fix that, don't ya. After you plug the probe in, just secure it in place by wrapping duck tape around the entire oximeter. Ya shouldn't have any problem at all with the probe coming loose after that.

I once used duck tape when the air inlet hose in my Honda disintegrated years ago. That worked just fine for years. Never had to replace the duck tape. It outlasted the original hose material. That's saying something since it was under the hood.

Regards,
Bill (kinda wondering himself how serious his recommendation should be taken)

NightHawkeye wrote:

snork1 wrote: . . . it also won't tell me when the funky connector disconnects . . .

Ya know duck tape can fix that, don't ya. After you plug the probe in, just secure it in place by wrapping duck tape around the entire oximeter. Ya shouldn't have any problem at all with the probe coming loose after that.

I once used duck tape when the air inlet hose in my Honda disintegrated years ago. That worked just fine for years. Never had to replace the duck tape. It outlasted the original hose material. That's saying something since it was under the hood.

Regards,
Bill (kinda wondering himself how serious his recommendation should be taken)

Snork,

Is the connector to the N395 different from what I showed in the photos ?

DSM

dsm wrote:Snork,

Is the connector to the N395 different from what I showed in the photos ?

DSM

The connector on the front panel of the N-395 is a D-sub but with flakey sliding contacts in a center strip instead of the usual robust pins. It uses the "push on the sides" to open jaws retainer.

Another thought I had was to replace the connector system at the front panel with a more standard micro-D-sub set up with pins and a more robust latching system. Of course that means I would have to replace the cable connector too.

I have a question for you guys with the N-395.

I am preparing a serial cable for linking to my notebook ready for doing software dev to capture data from my N-200.

Early on there was mention of a 15-pin connector. I didn't actually take a really close look at my N-200's serial port until this past w/e & it is not 15-pin but a standard and universal DB9 (same as most computers).

I then dug up some docs on the N400 & N1000 & they to talk of DB9.

Can someone just confirm to me that the N-395 does actually use a DB15 as the output serial connector ?

Puzzled

DSM

dsm wrote:Can someone just confirm to me that the N-395 does actually use a DB15 as the output serial connector ?

Guaranteed! Wired it myself. Wired one end to a 15 pin, and wired the other end to a 9 pin.

You can find the "official" details on the Nellcor website.

Regards,
Bill

dsm wrote:Puzzled

The N-395 has a number of independent outputs available, mostly analog I think. Rather than put all the analog ports on a different connector it looks like they chose to add 'em onto the serial port connector, hence the connector had to grow from 9-pins to the next larger size of 15-pins. Anyway, that's my take on it.

Regards,
Bill

Hello Snork1,
I certainly use to agree with this statement:

snork1 wrote:well the pulse ox is nice, but it has more beeps than a cheap radar detector going through a strip mall.
I think the software guy was paid by the number of tones that they made this Nellcor N-395 beep.

Fortunately, there is a solution in Section 4 of the Nellcor Service Manual. Almost everything you want to learn about calming that hyper-active toy is there, including how to turn the volume down to small beeps. For certain when you’re done making the adjustments you’ll begin to think you didn’t really buy this oximeter for the aggravation. I can’t for the life of me understand what the engineers were thinking when they created all those alarms and short cycles. Did they think someone life was on the line?

As for the loose connections, I use Nellcor’s DS-100 reusable probe and find that I need to wear a “pant-leg strap” (used when wearing winter pants on a bicycle to keep the cloth out of the chain) on my wrist to control the cable. I toss and turn so much at night that I find I push the probe around and sometimes pull it off with my bed-bouncing exercises. When this happens, the Nellcor would goes nuts, but now that I’ve permanently moved the delay to its maximum setting, turned off the reminder alarms and dropped the volume down to almost nothing, the number of times the Nellcor goes into Fire Alarm mode has dropped to near nothing, and the best part is you don't have to reset them each time you turn the machine on because you can use the new settings as the default values for your use.

As for connections, there is so much cable it is hard for me to think the loose fitting cable at the unit is causing the alarms. Before you go bending too many things, work through the Service Manual so you can get the beast to calm down. Then work on getting the probe stable on your finger. If the probe moves around on your finger, the unit needs to go through another cycle where it confirms a reading. If it doesn’t confirm the reading before the alarm cycle terminates the alarm-cycle kicks off its favorite one-note tune.

I don’t think I would leave the speaker disconnected because it gives you feedback when you’re changing settings. If you’ve got it disconnected, then consider putting back on until you go through the settings phase. When you’re doing the settings, look at the low side desaturation value and consider if you want that to be lower before it triggers an alarm. When the probe is moving around, it can cause the unit to think the oxygen saturation has dropped below the alarm lower limits when it fact it is going through another connection cycle.

Roger ,
Thanks for the tip on section 4. I will check into that. I get the impression the default settings can be changed from your description? Having to reset everything in the middle of the night if you get up to use the bathroom is really an issue. I definitely have some learning curve on this machine! Its probably NOT a good purchase for the non-technically oriented!

I am not sure why I would need the beeps for making the settings? The dome buttons have tactile feedback and I can read the results on the monitor.

I REALLY like the machine, so far with the speaker disconnected, and its easily reversible if I change my mind. I was thinking of adding a switch for REALLY turning the speaker on and off from outside of the box and independent of the beep happy software design.

Thats a VERY good tip on setting the delay time to max. I am also a restless sleeper and I am still trying to figure out why it seems to reset sometimes when I reseat the probe or put it back on after a bathroom break and sometimes I have to either hit the alarm off switch or even power it down to get it to a realistic setting again.

I grabbed one of my bike cuff velcro clips but it wasn't elastic and didn't work right. I am going to try an old "scrunchie" I found tucked in a drawer next for helping the wire stay in place. I was debating using tape or self-adhering ace bandage, but bathroom breaks might be problematic.

Last night I got weird results on the pulse ox....when it was working... and figured it was just not working right or something....Until I looked at my machine results and discovered indeed it WAS a bad night. I had taken my anti-RLS meds which I usually avoid, and now I am thinking there may be more to why I wake up groggy after taking that medicine. This pulse ox could really be a handy item once I figure it out!

I am still trying to find in the manual where it explains the two numbers under SPO2 when zooming into an area and moving the bar. Sometimes they range as wide as 82:95 with the bar in one spot. The low number seems to go really low occasionally. Any quick explanations to save me digging through the manual? (which I am off to start digging into now)

Thanks for ALL the tips!

OK, where in the manuals do I find how to read the "zoom" feature on the stored data, under "trends", especially the %SPO2 76:95 (or similar) that changes at each point as the bar scrolls across the stored data?

It is NOT the high-low alarm limit and does correspond with the graph going up and down. I can't seem to find ANY mention of the softkey "trends" feature in the manuals.

Thanks for any and all hints!

snork1 wrote:I am still trying to find in the manual where it explains the two numbers under SPO2 when zooming into an area and moving the bar. Sometimes they range as wide as 82:95 with the bar in one spot. The low number seems to go really low occasionally. Any quick explanations to save me digging through the manual? (which I am off to start digging into now)

Those two numbers are the range of SPO2 for the point your bar is at. It's a sampled data issue. Each pixel on your display represents not just a single measurement, but a number of time measurements. As you zoom in further the 82:95 spread should narrow. At the next zoom you might see 82:89 for instance. The next zoom, maybe 82:85. The oximeter records data every ten seconds (at least that's the best resolution shown with the software), but every pixel on your display represents a larger span of time.

One thing Roger and I have both observed is that sometimes deep desaturations occur quickly and sometimes they occur slowly. The slow desaturations are definitely apnea related and these can occur over a minute or two, sometimes even longer. For the quick deep desaturations we've speculated as to the cause, but have really don't know for sure. These could be physiological, as in circulatory issues, or they could simply be measurement issues.

Here's an example of a slow desaturation I saw last night which corresponds with a recorded apnea from the Encore Pro software:


Hope that makes things a little clearer.

Regards,
Bill

Thanks for the clarification on the "dual numbers" reading(xx:xx). I was starting to suspect it was something along those lines but I wasn't sure. I was also suprised by how much that spread can sometimes be in such a short time.

I think I am getting the machine pretty much dialed-in, thanks to the help here.

Last night I used a scrunchie around my wrist and the sensor wire and that worked out pretty well with my thrashing about, although I think I could fine tune that even further.

I fixed the loose connector problem at the face of the unit by using several layers of thin "scotch tape" around the connector so it fits a bit more snugly in the pocket. This makes a HUGE difference for keeping a clean connection. At least now I know not to use that type of D-sub connector and latch system in any of MY designs, which is actually very useful info for me.

I set the machine to 120 seconds before alarm, per suggestion here, and just made sure to punch the alarm button when my bathroom break took just over 120 seconds.

And I am absolutely delighted with my decision to unplug the speaker. I have not missed ANY of the beeps AT ALL for my use. When I was searching through the manuals I noted two things about the alarms. It does not allow you to change the default to alarms OFF, and they do indeed describe it as a feature that it beeps every 3 minutes to remind you that you turned the beeps off. Thank gawd the hardware designer anticipated how stupid THAT was and made the speaker easy to disconnect.

Anyway, I got a nice clean night of readings last night. I should be able to start trying out CPAP variables now and maybe trying out my Aveo TSD device again.

Hey, I just got a new job and will be back designing medical devices again in a couple of weeks, working on portable sonagram machines. Avionics and defense is just not for me. So all my fiddling with CPAP stuff is really just "job training".

Snork1 wrote:Hey, I just got a new job and will be back designing medical devices again in a couple of weeks, working on portable sonagram machines. Avionics and defense is just not for me. So all my fiddling with CPAP stuff is really just "job training".

Should we go out and buy stock in that company yet?

Congratulations!

Best wishes,

Den

snork1 wrote:Hey, I just got a new job and will be back designing medical devices again in a couple of weeks, working on portable sonagram machines. Avionics and defense is just not for me. So all my fiddling with CPAP stuff is really just "job training".

Ditto on the congratulations. Small projects like that are sure the most fun.

Regards,
Bill

snork1 wrote: I set the machine to 120 seconds before alarm, per suggestion here, and just made sure to punch the alarm button when my bathroom break took just over 120 seconds.

When I need to get out of bed during the night, I press the Alarm button, remove the probe and then press the Alarm button again. This tells the oximeter to relax until I get back. When I return, I just put the probe back on and dive back into the sack.

As for the reminder Alarm, that CAN be disabled. I have disabled it on my machine using the Service Manual procedure. However, you can’t disable the disconnect Alarm which is why I’ve turned my volume down to near nothing. Still, near-nothing isn’t nothing, so your room will be quieter than mine.

When I went through the Service Manual to change the defaults, the machine uses “Beeps” it returns to the key press commands. These return “Beeps” are the only indication you have that a default setting was changed. I don’t remember if it beeps when it doesn’t work or beeps when a command does work, but I know that I found some of the changes a little confusing at first, but knew what was happening because of how the machine responded. With all the default startup setting established to how I want them, I only have to turn the machine on and then connect the probe before turning off the light.

Glad to hear you are now getting some sleep again. It will go a long way when it comes time to making design decisions.